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Journal articles on the topic 'N-phenyl nitrones'

Author: Grafiati

Published: 18 May 2024

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1

Gallis, David E., James A. Warshaw, Bruce J. Acken, and DeLanson R. Crist. "Electronic Nature of α-Methoxy, Amino, Cyano, and Mercapto Nitrones." Collection of Czechoslovak Chemical Communications 58, no. 1 (1993): 125–41. http://dx.doi.org/10.1135/cccc19930125.

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The electronic nature of various C-substituted nitrones was investigated by IR spectroscopy and 13C NMR as well as MNDO calculations. These include α-methoxy nitrones (imidate N-oxides) RC(OMe)=N(O)t-Bu with R = p-MeOC6H4 (Ia), C6H5 (Ib), p-NO2C6H4 (Ic), and H (Id) and nitrones YCH=N(O)t-Bu with Y = CN (IIIa), n-BuS (IIIb), C6H5CH2NH (IIIc). Upfield 13C shifts of C(α), the iminyl (C=N) carbon, of imidate N-oxides I versus the corresponding imidates are less than the usual upfield shifts of imine N-oxides versus imines, suggesting less buildup of electron density on C(α) in the case of alcoxy nitrones. Charge density and π bond order values from MNDO calculations for C-methoxy-C-phenyl nitrones versus model systems confirm this result and indicate a more localized C=N π bond in nitrones bearing an α-methoxy group. For N-tert-butyl nitrones with an α heteroatom (nitrogen or sulfur), phenyl, or cyano group, C(α) shifts move downfield for π-donating groups and upfield for π-accepting groups. This "reverse substituent effect" as well as C=N stretching frequencies can also be readily explained by C=N π bond containment by lone pair groups. The reported enhanced cycloaddition reactivity of α-alkoxy nitrones and their electrochemical behavior are discussed in terms of HOMO energy levels.

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2

Marano, Stefania, Cristina Minnelli, Lorenzo Ripani, Massimo Marcaccio, Emiliano Laudadio, Giovanna Mobbili, Adolfo Amici, Tatiana Armeni, and Pierluigi Stipa. "Insights into the Antioxidant Mechanism of Newly Synthesized Benzoxazinic Nitrones: In Vitro and In Silico Studies with DPPH Model Radical." Antioxidants 10, no. 8 (July 29, 2021): 1224. http://dx.doi.org/10.3390/antiox10081224.

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Synthetic nitrone spin-traps are being explored as therapeutic agents for the treatment of a wide range of oxidative stress-related pathologies, including but not limited to stroke, cancer, cardiovascular, and neurodegenerative diseases. In this context, increasing efforts are currently being made to the design and synthesis of new nitrone-based compounds with enhanced efficacy. The most researched nitrones are surely the ones related to α-phenyl-tert-butylnitrone (PBN) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) derivatives, which have shown to possess potent biological activity in many experimental animal models. However, more recently, nitrones with a benzoxazinic structure (3-aryl-2H-benzo[1,4]oxazin-N-oxides) have been demonstrated to have superior antioxidant activity compared to PBN. In this study, two new benzoxazinic nitrones bearing an electron-withdrawing methoxycarbonyl group on the benzo moiety (in para and meta positions respect to the nitronyl function) were synthesized. Their in vitro antioxidant activity was evaluated by two cellular-based assays (inhibition of AAPH-induced human erythrocyte hemolysis and cell death in human retinal pigmented epithelium (ARPE-19) cells) and a chemical approach by means of the α,α-diphenyl-β-picrylhydrazyl (DPPH) scavenging assay, using both electron paramagnetic resonance (EPR) spectroscopy and UV spectrophotometry. A computational approach was also used to investigate their potential primary mechanism of antioxidant action, as well as to rationalize the effect of functionalization on the nitrones reactivity toward DPPH, chosen as model radical in this study. Further insights were also gathered by exploring the nitrone electrochemical properties via cyclic voltammetry and by studying their kinetic behavior by means of EPR spectroscopy. Results showed that the introduction of an electron-withdrawing group in the phenyl moiety in the para position significantly increased the antioxidant capacity of benzoxazinic nitrones both in cell and cell-free systems. From the mechanistic point of view, the calculated results closely matched the experimental findings, strongly suggesting that the H-atom transfer (HAT) is likely to be the primary mechanism in the DPPH quenching.

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3

Chamorro, Beatriz, Iwona E. Głowacka, Joanna Gotkowska, Rafał Gulej, Dimitra Hadjipavlou-Litina, Francisco López-Muñoz, José Marco-Contelles, Dorota G. Piotrowska, and María Jesús Oset-Gasque. "Nucleobase-Derived Nitrones: Synthesis and Antioxidant and Neuroprotective Activities in an In Vitro Model of Ischemia–Reperfusion." International Journal of Molecular Sciences 23, no. 6 (March 21, 2022): 3411. http://dx.doi.org/10.3390/ijms23063411.

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Herein, we report the synthesis, antioxidant, and neuroprotective properties of some nucleobase-derived nitrones named 9a–i. The neuroprotective properties of nitrones, 9a–i, were measured against an oxygen-glucose-deprivation in vitro ischemia model using human neuroblastoma SH-SY5Y cells. Our results indicate that nitrones, 9a–i, have better neuroprotective and antioxidant properties than α-phenyl-N-tert-butylnitrone (PBN) and are similar to N-acetyl-L-cysteine (NAC), a well-known antioxidant and neuroprotective agent. The nitrones with the highest neuroprotective capacity were those containing purine nucleobases (nitrones 9f, g, B = adenine, theophylline), followed by nitrones with pyrimidine nucleobases with H or F substituents at the C5 position (nitrones 9a, c). All of these possess EC50 values in the range of 1–6 μM and maximal activities higher than 100%. However, the introduction of a methyl substituent (nitrone 9b, B = thymine) or hard halogen substituents such as Br and Cl (nitrones 9d, e, B = 5-Br and 5-Cl uracil, respectively) worsens the neuroprotective activity of the nitrone with uracil as the nucleobase (9a). The effects on overall metabolic cell capacity were confirmed by results on the high anti-necrotic (EC50′s ≈ 2–4 μM) and antioxidant (EC50′s ≈ 0.4–3.5 μM) activities of these compounds on superoxide radical production. In general, all tested nitrones were excellent inhibitors of superoxide radical production in cultured neuroblastoma cells, as well as potent hydroxyl radical scavengers that inhibit in vitro lipid peroxidation, particularly, 9c, f, g, presenting the highest lipoxygenase inhibitory activity among the tested nitrones. Finally, the introduction of two nitrone groups at 9a and 9d (bis-nitronas 9g, i) did not show better neuroprotective effects than their precursor mono-nitrones. These results led us to propose nitrones containing purine (9f, g) and pyrimidine (9a, c) nucleobases as potential therapeutic agents for the treatment of cerebral ischemia and/or neurodegenerative diseases, leading us to further investigate their effects using in vivo models of these pathologies.

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4

Nakajima, Akira, Yuto Ueda, Nobuyuki Endoh, Kunihiko Tajima, and Keisuke Makino. "Electron spin resonance analysis of the oxidation reactions of nitrone type spin traps with gold(III) ion." Canadian Journal of Chemistry 83, no. 8 (August 1, 2005): 1178–84. http://dx.doi.org/10.1139/v05-132.

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When cyclic nitrones, such as 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), 4-phenyl-5,5-dimethyl-1- pyrroline-N-oxide (PDMPO), and 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO) were mixed with hydrogen tetrachloro aurate(III), DMPOX (5,5-dimethyl-1-pyrrolid-2-one-N-oxyl) type free radicals appeared with the precipitation of Au(0). The reaction did not proceed with noncyclic nitrones, such as N-tert-butyl-α-phenyl-nitrone (PBN) and α-(4-pyridyl-1-oxide)-N-tert-butyl-nitrone (POBN). The order of the HAuCl4 decrease was DMPO > PDMPO > M4PO. The reaction was depressed by the addition of chloride or hydroxide ions. 1-Hydroxy-5,5-dimethyl-1-pyrrolid-2-one (HDMPN), the precursor of DMPOX, was also oxidized to DMPOX by HAuCl4. Every step of the gold reduction from Au(III) to Au(0) can be used for the oxidation of HDMPN to DMPOX. Based on these and previous results, the reaction was assumed to proceed by the following scheme consisting of a ligand exchange interaction of AuCl4 with >N+O in DMPO, then nucleophilic addition of a water molecule to DMPO, then the stepwise intramolecular transfer of three electrons from DMPO to Au(III), and finally the precipitation of Au(0). Key words: ESR, nitrone, spin traps, DMPO, DMPOX, gold(III) ion.

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5

Rosselin, Marie, Fanny Choteau, Kamal Zéamari, Kevin M. Nash, Amlan Das, Robert Lauricella, Elisabeth Lojou, Béatrice Tuccio, Frederick A. Villamena, and Grégory Durand. "Reactivities of Substituted α-Phenyl-N-tert-butyl Nitrones." Journal of Organic Chemistry 79, no. 14 (July 3, 2014): 6615–26. http://dx.doi.org/10.1021/jo501121g.

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6

Kliegel, W., L. Preu, Steven J. Rettig, and James Trotter. "Structural studies of organoboron compounds. XXI. Crystal and molecular structures of 3-(phenylmethylidene)-4-methyl-1-phenyl-2,6,7-trioxa-3-azonia-1-boratabicyclo-[2.2.2]octane and N-(4-nitrophenylmethylidene)-5-methyl-2-phenyl-1,3-dioxa-2-bora-5-cyclohexaneamine N-oxide." Canadian Journal of Chemistry 63, no. 2 (February 1, 1985): 509–15. http://dx.doi.org/10.1139/v85-083.

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Crystals of 3-(phenylmethylidene)-4-methyl-1-phenyl-2,6,7-trioxa-3-azonia-1-boratabicyclo[2.2.2]octane are orthorhombic, a = 8.0732(7), b = 11.8499(10), c = 31.679(2) Å, Z = 8, space group Pbca, and those of N-(4-nitrophenylmethylidene)-5-methyl-2-phenyl-1,3-dioxa-2-bora-5-cyclohexaneamine N-oxide are monoclinic, a = 6.1873(6), b = 23.206(2), c = 11.3081(11) Å, β = 92.326(5)°, Z = 4, space group P21/n. Both structures were solved by direct methods and were refined by full-matrix least-squares procedures to final R values of 0.041 and 0.036 for 943 and 1679 reflections with I ≥ 3σ(I), respectively. Both compounds are condensation products of bis(hydroxyalkyl)nitrones and phenylboronic acid. 3-(Phenyl-methylidene)-4-methyl-1-phenyl-2,6,7-trioxa-3-azonia-1-boratabicyclo[2.2.2]octane was found to possess a bicyclic structure resulting from intramolecular O → B coordination (O—B = 1.604(7) Å) and is the first such bicyclic boron compound to be structurally characterized. In N-(4-nitrophenylmethylidene)-5-methyl-2-phenyl-1,3-dioxa-2-bora-5-cyclohexaneamine N-oxide, which has weakened nitrone basicity, the O → B interaction does not occur, resulting in a monocyclic system incorporating a trigonal planar boron atom.

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7

Mekheimer, Ramadan A., Khadijah Al-Zaydi, Mahmoud A. A. Ibrahim, Asma Al-Shamary, and Kamal Sadek. "Regio- and stereoselective 1,3-dipolar cycloaddition reactions of C-aryl (or hetaryl)-N-phenylnitrones to monosubstituted ylidene malononitriles and 4-benzylidene-2-phenyloxazol-5(4H)-one." Zeitschrift für Naturforschung B 72, no. 5 (May 1, 2017): 317–26. http://dx.doi.org/10.1515/znb-2016-0263.

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AbstractThe first example of 1,3-dipolar cycloaddition reactions of C-aryl (or hetaryl)-N-phenylnitrones to monosubstituted ylidene malononitriles and 4-benzylidene-2-phenyl-oxazol-5(4H)-one is described. The reaction of C-(4-(dimethylamino)phenyl)-N-phenyl-nitrone (1a) with 2-(4-substituted-benzylidene)malononitriles 2a, b in dry toluene, in the absence of catalyst, at reflux temperature furnished the novel cycloadducts 2-(3-aryl-2-phenyl-2,3-dihydro-1,2,4-oxadiazol-5-yl)-3-(4-methoxyphenyl)acrylonitriles 3a, b. Refluxing C-aryl (or hetaryl)-N-phenylnitrones 1b–i with 2-(4-methoxy-benzylidene)malononitrile (2a) in dry toluene, in the absence of catalyst, gave the unexpected 2-cyano-3-(4-methoxyphenyl)-acrylamide (5), as the sole product. On the other hand, refluxing 4-benzylidene-2-phenyloxazol-5(4H)-one (7) with an equimolar amount of C-aryl (or hetaryl)-N-phenyl-nitrones 1a–c, f–i in absolute EtOH afforded the previously unknown 5-anilino-4-benzoyl-2-phenyloxazole (10), as the only isolable product. The resulting products were formed with a high degree of regio- and stereoselectivity. Quantum chemical calculations were performed to verify stereoselectivity of the studied reaction. A mechanistic proposal is presented to rationalize the formation of these products.

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8

Kliegel, Wolfgang, Jörg Metge, Steven J. Rettig, and James Trotter. "Aromatic aldonitrones of 2-(hydroxyamino)benzyl alcohol and their cyclic isomers. Crystal and molecular structures of a 1-hydroxy-1,2-dihydro-4H-3,1-benzoxazine, a boron chelate, and its parent nitrone ligand." Canadian Journal of Chemistry 76, no. 4 (April 1, 1998): 389–99. http://dx.doi.org/10.1139/v98-023.

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The synthesis of a series of C-aryl-N-[2-(hydroxymethyl)phenyl]nitrones, 5 (that can also exist under certain conditions as isomeric 1-hydroxy-2-aryl-1,2-dihydro-4H-3,1-benzoxazines, 8), via 2-(hydroxyamino)benzyl alcohol, 4, and their subsequent reactions with oxybis(diphenylborane), (Ph2B)2O, leading to the 5-(arylmethylene)-7,7-diphenyl-6,8-dioxa- 5-azonia-7-borata-5H-6,7,8,9-tetrahydrobenzocyclo- heptenes 6 are described. Crystals of 1-hydroxy-2- (4-methoxyphenyl)- 1,2-dihydro-4H-3,1-benzoxazine, 8b, are monoclinic, a = 9.379(2), b = 10.699(2), c = 12.9392(7) Å, β = 99.916(2)°, Z = 4 (two independent molecules), space group Pa; those of C-[4-(dimethylamino)phenyl]-N-[(2-hydroxymethyl)phenyl]nitrone, 5c, are monoclinic, a = 7.687(1), b = 7.891(1), c = 11.5053(9) Å, β = 92.781(9)°, Z = 2, space group P21; and those of 5-[4-(dimethylamino)phenylmethylene]-7,7-diphenyl-6,8-dioxa-5-azonia-7-borata-5H-6,7,8,9- tetrahydro-benzocycloheptene, 6a, are monoclinic, a = 10.771(1), b = 13.1057(9), c = 16.8724(7) Å, β = 90.005(5)°, Z = 4, space group P21/n. The structures were solved by direct methods and refined by full-matrix least-squares procedures to R(F2) = 0.120 (Rw(F2) = 0.135) for all 3149 reflections (R(F) = 0.071, Rw(F) = 0.063 for 1500 reflections with I >3 σ (I)) for 8b and R(F) = 0.035 and 0.036 (Rw(F) = 0.031 and 0.038) for 1071 and 3594 reflections with I >3 σ (I), respectively, for 5c and 6a. Compound 8b is the first structurally characterized 1-hydroxy-1,2-dihydro-4H-3,1-benzoxazine derivative and 6a features a relatively rare seven-membered boron-containing heterocycle.Key words: C-aryl-N-[2-(hydroxymethyl)phenyl]nitrones, 1-hydroxy-2-aryl-1,2-dihydro-4H-3,1-benzoxazines, organoboron compounds, crystal structures

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9

Suda, Kohji, Toshio Tsujimoto, and Masashige Yamauchi. "13C and1H NMR of Arylnitrones. Substituent Effects of α-Phenyl-N-(p-substituted phenyl)nitrones." Bulletin of the Chemical Society of Japan 60, no. 10 (October 1987): 3607–11. http://dx.doi.org/10.1246/bcsj.60.3607.

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10

Chamorro, Beatriz, David García-Vieira, Daniel Diez-Iriepa, Estíbaliz Garagarza, Mourad Chioua, Dimitra Hadjipavlou-Litina, Francisco López-Muñoz, José Marco-Contelles, and María Jesús Oset-Gasque. "Synthesis, Neuroprotection, and Antioxidant Activity of 1,1′-Biphenylnitrones as α-Phenyl-N-tert-butylnitrone Analogues in In Vitro Ischemia Models." Molecules 26, no. 4 (February 20, 2021): 1127. http://dx.doi.org/10.3390/molecules26041127.

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Herein, we report the neuroprotective and antioxidant activity of 1,1′-biphenyl nitrones (BPNs) 1–5 as α-phenyl-N-tert-butylnitrone analogues prepared from commercially available [1,1′-biphenyl]-4-carbaldehyde and [1,1′-biphenyl]-4,4′-dicarbaldehyde. The neuroprotection of BPNs1-5 has been measured against oligomycin A/rotenone and in an oxygen–glucose deprivation in vitro ischemia model in human neuroblastoma SH-SY5Y cells. Our results indicate that BPNs 1–5 have better neuroprotective and antioxidant properties than α-phenyl-N-tert-butylnitrone (PBN), and they are quite similar to N-acetyl-L-cysteine (NAC), which is a well-known antioxidant agent. Among the nitrones studied, homo-bis-nitrone BPHBN5, bearing two N-tert-Bu radicals at the nitrone motif, has the best neuroprotective capacity (EC50 = 13.16 ± 1.65 and 25.5 ± 3.93 μM, against the reduction in metabolic activity induced by respiratory chain blockers and oxygen–glucose deprivation in an in vitro ischemia model, respectively) as well as anti-necrotic, anti-apoptotic, and antioxidant activities (EC50 = 11.2 ± 3.94 μM), which were measured by its capacity to reduce superoxide production in human neuroblastoma SH-SY5Y cell cultures, followed by mononitrone BPMN3, with one N-Bn radical, and BPMN2, with only one N-tert-Bu substituent. The antioxidant activity of BPNs1-5 has also been analyzed for their capacity to scavenge hydroxyl free radicals (82% at 100 μM), lipoxygenase inhibition, and the inhibition of lipid peroxidation (68% at 100 μM). Results showed that although the number of nitrone groups improves the neuroprotection profile of these BPNs, the final effect is also dependent on the substitutent that is being incorporated. Thus, BPNs bearing N-tert-Bu and N-Bn groups show better neuroprotective and antioxidant properties than those substituted with Me. All these results led us to propose homo-bis-nitrone BPHBN5 as the most balanced and interesting nitrone based on its neuroprotective capacity in different neuronal models of oxidative stress and in vitro ischemia as well as its antioxidant activity.

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11

Durand, Grégory, Marie Rosselin, Pierre-André Klein, Kamal Zéamari, Fanny Choteau, and Béatrice Tuccio. "α-Phenyl-N-cyclohexyl Nitrones: Preparation and Use as Spin-Traps." Journal of Organic Chemistry 82, no. 1 (December 20, 2016): 135–42. http://dx.doi.org/10.1021/acs.joc.6b02262.

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12

Diez-Iriepa, Daniel, Beatriz Chamorro, Marta Talaván, Mourad Chioua, Isabel Iriepa, Dimitra Hadjipavlou-Litina, Francisco López-Muñoz, José Marco-Contelles, and María Jesús Oset-Gasque. "Homo-Tris-Nitrones Derived from α-Phenyl-N-tert-butylnitrone: Synthesis, Neuroprotection and Antioxidant Properties." International Journal of Molecular Sciences 21, no. 21 (October 26, 2020): 7949. http://dx.doi.org/10.3390/ijms21217949.

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Herein we report the synthesis, antioxidant and neuroprotective power of homo-tris-nitrones (HTN) 1-3, designed on the hypothesis that the incorporation of a third nitrone motif into our previously identified homo-bis-nitrone 6 (HBN6) would result in an improved and stronger neuroprotection. The neuroprotection of HTNs 1-3, measured against oligomycin A/rotenone, showed that HTN2 was the best neuroprotective agent at a lower dose (EC50 = 51.63 ± 4.32 μM), being similar in EC50 and maximal activity to α-phenyl-N-tert-butylnitrone (PBN) and less potent than any of HBNs 4-6. The results of neuroprotection in an in vitro oxygen glucose deprivation model showed that HTN2 was the most powerful (EC50 = 87.57 ± 3.87 μM), at lower dose, but 50-fold higher than its analogous HBN5, and ≈1.7-fold less potent than PBN. HTN3 had a very good antinecrotic (IC50 = 3.47 ± 0.57 μM), antiapoptotic, and antioxidant (EC50 = 6.77 ± 1.35 μM) profile, very similar to that of its analogous HBN6. In spite of these results, and still being attractive neuroprotective agents, HTNs 2 and 3 do not have better neuroprotective properties than HBN6, but clearly exceed that of PBN.

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13

Diez-Iriepa, Daniel, Damijan Knez, Stanislav Gobec, Isabel Iriepa, Cristóbal de los Ríos, Isaac Bravo, Francisco López-Muñoz, José Marco-Contelles, and Dimitra Hadjipavlou-Litina. "Polyfunctionalized α-Phenyl-tert-butyl(benzyl)nitrones: Multifunctional Antioxidants for Stroke Treatment." Antioxidants 11, no. 9 (August 31, 2022): 1735. http://dx.doi.org/10.3390/antiox11091735.

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Nowadays, most stroke patients are treated exclusively with recombinant tissue plasminogen activator, a drug with serious side effects and limited therapeutic window. For this reason, and because of the known effects of oxidative stress on stroke, a more tolerable and efficient therapy for stroke is being sought that focuses on the control and scavenging of highly toxic reactive oxygen species by appropriate small molecules, such as nitrones with antioxidant properties. In this context, herein we report here the synthesis, antioxidant, and neuroprotective properties of twelve novel polyfunctionalized α-phenyl-tert-butyl(benzyl)nitrones. The antioxidant capacity of these nitrones was investigated by various assays, including the inhibition of lipid peroxidation induced by AAPH, hydroxyl radical scavenging assay, ABTS+-decoloration assay, DPPH scavenging assay, and inhibition of soybean lipoxygenase. The inhibitory effect on monoamine oxidases and cholinesterases and inhibition of β-amyloid aggregation were also investigated. As a result, (Z)-N-benzyl-1-(2-(3-(piperidin-1-yl)propoxy)phenyl)methanimine oxide (5) was found to be one of the most potent antioxidants, with high ABTS+ scavenging activity (19%), and potent lipoxygenase inhibitory capacity (IC50 = 10 µM), selectively inhibiting butyrylcholinesterase (IC50 = 3.46 ± 0.27 µM), and exhibited neuroprotective profile against the neurotoxicant okadaic acid in a neuronal damage model. Overall, these results pave the way for the further in-depth analysis of the neuroprotection of nitrone 5 in in vitro and in vivo models of stroke and possibly other neurodegenerative diseases in which oxidative stress is identified as a critical player.

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14

Möhrle, H., and M. Jeandrée. "Chinazolinderivate durch Cyclodehydrierung von N-(2-substituierten Aryl)-Piperidinen / Quinazoline Derivatives by Cyclodehydrogenation of N-(2-Substituted Aryl)-Piperidines." Zeitschrift für Naturforschung B 54, no. 12 (December 1, 1999): 1577–88. http://dx.doi.org/10.1515/znb-1999-1217.

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Dehydrogenation of the N-[2-(aminocarbonyl)phenyl]piperidines 1 -5 using Hg(II)-EDTA, generated the quinazolinones 6 -9 . Increasing size of the 4-substituent in the piperidine decreased the oxidation rate and the product yield.N-[2-(Hydroxyiminomethyl)phenyl]piperidines 18-22 showed a different behaviour. While 18 with H g(II)-EDTA in water produced the oxime lactam 24 in quantitative yield, the 4- substituted piperidines 19-21 caused not only a lower reaction rate but also an altered product pattern. The double dehydrogenation to lactams was reduced and the cyclic nitrones, formed by two electron withdrawal, became dominant. From the spiro compounds 21 and 22, solely the quinazoline-N-oxides 29 and 30 resulted. The mechanism of the reactions is discussed.

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15

Chamorro, Beatriz, Sara Izquierdo-Bermejo, María Dolores Martín-de-Saavedra, Francisco López-Muñoz, Mourad Chioua, José Marco-Contelles, and María Jesús Oset-Gasque. "Neuroprotective and Antioxidant Properties of Cholestero Nitrone ChN2 and QuinolylNitrone QN23 in an Experimental Model of Cerebral Ischemia: Involvement of Necrotic and Apoptotic Cell Death." Antioxidants 12, no. 7 (June 29, 2023): 1364. http://dx.doi.org/10.3390/antiox12071364.

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Ischemic stroke is the leading cause of disability and the second leading cause of death worldwide. However, current therapeutic strategies are scarce and of limited efficacy. The abundance of information available on the molecular pathophysiology of ischemic stroke has sparked considerable interest in developing new neuroprotective agents that can target different events of the ischemic cascade and may be used in combination with existing treatments. In this regard, nitrones represent a very promising alternative due to their renowned antioxidant and anti-inflammatory effects. In this study, we aimed to further investigate the neuroprotective effects of two nitrones, cholesteronitrone 2 (ChN2) and quinolylnitrone 23 (QN23), which have previously shown great potential for the treatment of stroke. Using an experimental in vitro model of cerebral ischemia, we compared their anti-necrotic, anti-apoptotic, and antioxidant properties with those of three reference compounds. Both ChN2 and QN23 demonstrated significant neuroprotective effects (EC50 = 0.66 ± 0.23 μM and EC50 = 2.13 ± 0.47 μM, respectively) comparable to those of homo-bis-nitrone 6 (HBN6) and N-acetylcysteine (NAC) and superior to those of α-phenyl-N-tert-butylnitrone (PBN). While primarily derived from the nitrones’ anti-necrotic capacities, their anti-apoptotic effects at high concentrations and antioxidant powers—especially in the case of QN23—also contribute to their neuroprotective effects.

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16

Downey, C. Wade, Erin N. Maxwell, and Danielle N. Confair. "Silyl triflate-accelerated additions of catalytically generated zinc acetylides to N-phenyl nitrones." Tetrahedron Letters 55, no. 35 (August 2014): 4959–61. http://dx.doi.org/10.1016/j.tetlet.2014.07.015.

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17

Al-Rawi, Jasmin M. A., Salim Y. Hanna, and Amer A. Al-Rhman. "Solvent effects on the 1H NMR spectra of some α-(2-hydroxy-1-phenyl)-N-(4-substituted phenyl)nitrones." Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 51, no. 14 (December 1995): 2585. http://dx.doi.org/10.1016/0584-8539(95)01484-5.

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18

Janzen, Edward G., and Coit M. Dubose. "Electron Impact Mass Spectra of Some Substituted C-Phenyl N-tert-Butyl Nitrones (PBN's)." Analytical Letters 26, no. 12 (December 1993): 2661–66. http://dx.doi.org/10.1080/00032719308017982.

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19

Deletraz, Anaïs, Béatrice Tuccio, Julien Roussel, Maud Combes, Catherine Cohen-Solal, Paul-Louis Fabre, Patrick Trouillas, Michel Vignes, Noelle Callizot, and Grégory Durand. "Para-Substituted α-Phenyl-N-tert-butyl Nitrones: Spin-Trapping, Redox and Neuroprotective Properties." ACS Omega 5, no. 48 (November 20, 2020): 30989–99. http://dx.doi.org/10.1021/acsomega.0c03907.

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20

Rosselin, Marie, Béatrice Tuccio, Pierre Pério, Frederick A. Villamena, Paul-Louis Fabre, and Grégory Durand. "Electrochemical and Spin-Trapping Properties of para-substituted α-Phenyl-N-tert-butyl Nitrones." Electrochimica Acta 193 (March 2016): 231–39. http://dx.doi.org/10.1016/j.electacta.2016.02.038.

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21

Marco-Contelles, José. "α-Phenyl-N-tert-Butylnitrone and Analogous α-Aryl-N-alkylnitrones as Neuroprotective Antioxidant Agents for Stroke." Antioxidants 13, no. 4 (April 7, 2024): 440. http://dx.doi.org/10.3390/antiox13040440.

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The recent advances in research on the use of the antioxidant and neuroprotective agent α-phenyl-N-tert-butylnitrone (PBN) for the therapy of stroke have been reviewed. The protective effect of PBN in the transient occlusion of the middle cerebral artery (MCAO) has been demonstrated, although there have been significant differences in the neuronal salvaging effect between PBN-treated and untreated animals, each set of data having quite large inter-experimental variation. In the transient forebrain ischemia model of gerbil, PBN reduces the mortality after ischemia and the neuronal damage in the hippocampal cornu ammonis 1 (CA1) area of the hippocumpus caused by ischemia. However, PBN fails to prevent postischemic CA1 damage in the rat. As for focal cerebral ischemia, PBN significantly reduces cerebral infarction and decreases neurological deficit after ischemia using a rat model of persistent MCAO in rats. Similarly, the antioxidant and neuroprotective capacity of a number of PBN-derived nitrones prepared in the author’s laboratory have also been summarized here, showing their high potential therapeutic power to treat stroke.

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22

Downey, C. Wade, Erin N. Maxwell, and Danielle N. Confair. "ChemInform Abstract: Silyl Triflate-Accelerated Additions of Catalytically Generated Zinc Acetylides to N-Phenyl Nitrones." ChemInform 46, no. 6 (January 23, 2015): no. http://dx.doi.org/10.1002/chin.201506076.

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23

Marano, Stefania, Cristina Minnelli, Giovanna Mobbili, Emiliano Laudadio, and Pierluigi Stipa. "Synthesis and Evaluation of New Nitrone-Based Benzoxazinic Antioxidants." Medical Sciences Forum 2, no. 1 (November 30, 2020): 17. http://dx.doi.org/10.3390/cahd2020-08610.

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Oxidative stress is often the cause of a wide range of human chronic pathologies including, but not limited to, stroke and cardiovascular and neurodegenerative diseases. In this setting, increasing efforts are currently being devoted to the design and synthesis of new derivatives with enhanced antioxidant efficacy. Among all the potential molecules of interest, synthetic nitrone spin-traps have attracted a great deal of research attention, particularly due to their dual function as effective inhibitors of oxidative stress and damage and as analytical tools for the detection and characterization of free radicals by means of the electron paramagnetic resonance (EPR) spectroscopy spin trapping technique. In this study, two derivatives of benzoxazinic nitrones (3-aryl-2H-benzo[1,4]oxazin-N-oxides) bearing an electron-withdrawing methyl-acetate group on the benzo moiety (in para and meta positions with respect to the nitronyl function) were synthesized. Their in vitro antioxidant activity was evaluated by means of the α,α-diphenyl-β-picrylhydrazyl radical (DPPH) scavenging assay, and their inhibitory effects on the erythrocyte hemolysis induced by the water-soluble free radical initiator 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) compared. In addition, EPR was employed to monitor the decay profiles of DPPH to evaluate the kinetic behavior of the different antioxidants tested. Results showed that the presence and the position of the electron-withdrawing methyl-acetate group strongly affects the radical scavenging activity of nitrones. In particular, the newly synthesized para-substituted derivative, when compared to both the meta-substituted isomer and the unsubstituted parent compound, acts as a more effective antioxidant both in cell and cell-free systems. Overall, these results clearly show that the introduction of an electron-withdrawing group on the phenyl moiety significantly increased the antioxidant capacity of benzoxazinic nitrones, thus showing exciting opportunities in the search for new therapeutic agents in the treatment of diseases associated with oxidative stress.

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24

Matsunaga, Y., N. Kamiyama, and Y. Nakayasu. "Liquid Crystalline Properties of Mixtures Composed of N-[4-(Dimethylamino)phenyl]- and N-(4-Nitrophenyl)-α-(4-alkoxyphenyl) nitrones." Molecular Crystals and Liquid Crystals 147, no. 1 (January 1987): 85–97. http://dx.doi.org/10.1080/00268948708084626.

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25

Jayapradha, S. R., and S. Muthusubramanian. "Novel Rearrangement During the Reaction of Diethylmalonate with α-(5-Substituted 2-hydroxyphenyl)-N-phenyl Nitrones." Synthetic Communications 40, no. 3 (January 6, 2010): 434–41. http://dx.doi.org/10.1080/00397910902985481.

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26

Deletraz, Anaïs, Kamal Zéamari, Kangyu Hua, Maud Combes, Frederick A. Villamena, Béatrice Tuccio, Noelle Callizot, and Grégory Durand. "Substituted α-Phenyl and α-Naphthlyl-N-tert-butyl Nitrones: Synthesis, Spin-Trapping, and Neuroprotection Evaluation." Journal of Organic Chemistry 85, no. 9 (April 8, 2020): 6073–85. http://dx.doi.org/10.1021/acs.joc.0c00563.

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27

Chang, Zen Yu, and Robert M. Coates. "Enantioselective synthesis of primary amines via Grignard additions to stereogenic N-(.alpha.-phenyl-.beta.-(benzyloxy)ethyl)nitrones." Journal of Organic Chemistry 55, no. 11 (May 1990): 3475–83. http://dx.doi.org/10.1021/jo00298a019.

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28

Bulut, Gülen, Mehmet Oktav, and Mert Ulgen. "The stability studies andin vitro hepatic microsomal metabolism of some α-phenyl-N-substituted nitrones in rats." European Journal of Drug Metabolism and Pharmacokinetics 29, no. 4 (December 2004): 237–48. http://dx.doi.org/10.1007/bf03190606.

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29

Aurich, Hans Günter, and Michael Soeberdt. "Darstellung enantiomerenreiner 3-Oxa-2,7-diazabicyclo[3.3.0]octane und ihre Umwandlung in andere bicyclische Ringsysteme/Preparation of Pure Enantiomeric 3-Oxa-2,7-diazabicyclo[3.3.0]octanes and their Conversion to Other Bicyclic Ring-Systems." Zeitschrift für Naturforschung B 54, no. 1 (January 1, 1999): 87–95. http://dx.doi.org/10.1515/znb-1999-0117.

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Pure Enantiomeric (S)-N-benzylalaninol (R1 = Me) and (S)-N-benzylvalinol (R1 = i-Pr) were allylated with Br-CH2-CH=CR2R3 (R2 = R3 = H; R2 = Ph, R3 = H; R2 = R3 = Ph). Swern oxidation followed by treatment with methylhydroxylamine afforded nitrones 6 (Me- N(O)=CH-CHR1-N(CH2Ph)CH2-CH=CR2R3) which underwent an intramolecular 1,3-dipolar cycloaddition providing 3-oxa-2,7-diazabicyclo[3.3.0]octanes, e.g. (1R,5R,8S)-7-benzyl-2,8- dimethyl-3-oxa-2,7-diazabicyclo[3.3.0]octane 7a (R1 = Me, R2 = R3 = H) and (1R,4R,5R,8S)- 7-benzyl-2,8-dimethyl-4-phenyl-3-oxa-2,7-diazabicyclo[3.3.0]-octane 7b (R1 = Me, R2 = Ph, R3 = H).Reductive ring opening of 7a and 7b afforded the corresponding a-hydroxyalkylated pyrrolidines (9a: R2 = H or 9b: R2 = Ph. resp.). Condensation of these compounds with benzaldehyde yielded a mixture of diastereomeric 4-oxa-2,8-diazabicyclo[4.3.0]- nonanes: 10a/11a (1R,3S,6R,9S)/(1R,3R,6R,9S) R1 = Me, R2 = R3 = H and 10b /lib (1R,3S,5R,6R,9S)/(1R,3R,5R,6R,9S) R1 = Me, R2 = Ph, R3 = H. Pyrrolidine 9b was converted to the mesylate which formed (1R,4S,5R,7S)-3-benzyl-4,6-dimethyl-7-phenyl-3,6-diazabicyclo[3.2.0]heptane 13 along with (4R,5S)-1-benzyl-3,5-dimethyl-4-styryl-imidazolidine 15 upon treatment with sodium hydroxide.

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30

Haire, D. Larry, Uwe M. Oehler, H. Duane Goldman, Robert L. Dudley, and Edward G. Janzen. "The first 1H and 14N ENDOR spectra of an oxygen-centered radical adduct of DMPO-type nitrones." Canadian Journal of Chemistry 66, no. 9 (September 1, 1988): 2395–402. http://dx.doi.org/10.1139/v88-377.

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We report the first 1H and 14N electron nuclear double resonance (ENDOR) spectra of oxygen-centered radical adducts (i.e., derived from the addition of tert-butoxyl radicals) of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as well as the related cyclic nitrones: 4-phenyl-5,5-dimethyl-1-pyrroline-N-oxide (4-Ph-DMPO) and 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO). Features of the electron paramagnetic resonance (EPR) and ENDOR spectra of these cyclic (pyrrolidine) aminoxyl (nitroxide) species along with some deuterated analogues in liquid toluene solutions are highlighted. For instance, we found several long-range γ-H hyperfine splittings (HFS's) detectable by ENDOR that provide unique spectral signatures for these radical adducts. Conformational assignments of the pyrrolidine aminoxyl structures based upon the EPR and ENDOR findings are also discussed. Signs of the various hyperfine splittings (i.e., aN, [Formula: see text]) investigated by cross-relaxation intensity sequence patterns (CRISP) in the ENDOR spectra are also presented.

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31

Jayapradha, S. R., and S. Muthusubramanian. "ChemInform Abstract: Novel Rearrangement During the Reaction of Diethylmalonate with α-(5-Substituted 2-Hydroxyphenyl)-N-phenyl Nitrones." ChemInform 41, no. 25 (June 22, 2010): no. http://dx.doi.org/10.1002/chin.201025052.

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32

McCaig, Catherine, Paris Ataliotis, Anan Shtaya, Ayan S. Omar, A. Richard Green, Clive N. Kind, Anthony C. Pereira, et al. "Induction of the cell survival kinase Sgk1: A possible novel mechanism for α-phenyl-N-tert-butyl nitrone in experimental stroke." Journal of Cerebral Blood Flow & Metabolism 39, no. 6 (December 20, 2017): 1111–21. http://dx.doi.org/10.1177/0271678x17746980.

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Nitrones (e.g. α-phenyl-N-tert-butyl nitrone; PBN) are cerebroprotective in experimental stroke. Free radical trapping is their proposed mechanism. As PBN has low radical trapping potency, we tested Sgk1 induction as another possible mechanism. PBN was injected (100 mg/kg, i.p.) into adult male rats and mice. Sgk1 was quantified in cerebral tissue by microarray, quantitative RT-PCR and western analyses. Sgk1+/+ and Sgk1−/− mice were randomized to receive PBN or saline immediately following transient (60 min) occlusion of the middle cerebral artery. Neurological deficit was measured at 24 h and 48 h and infarct volume at 48 h post-occlusion. Following systemic PBN administration, rapid induction of Sgk1 was detected by microarray (at 4 h) and confirmed by RT-PCR and phosphorylation of the Sgk1-specific substrate NDRG1 (at 6 h). PBN-treated Sgk1+/+ mice had lower neurological deficit ( p < 0.01) and infarct volume ( p < 0.01) than saline-treated Sgk1+/+ mice. PBN-treated Sgk1−/− mice did not differ from saline-treated Sgk1−/− mice. Saline-treated Sgk1−/− and Sgk1+/+ mice did not differ. Brain Sgk3:Sgk1 mRNA ratio was 1.0:10.6 in Sgk1+/+ mice. Sgk3 was not augmented in Sgk1−/− mice. We conclude that acute systemic treatment with PBN induces Sgk1 in brain tissue. Sgk1 may play a part in PBN-dependent actions in acute brain ischemia.

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33

Haire, D. Larry, Yashige Kotake, and Edward G. Janzen. "An EPR/ENDOR study of aminoxyls (nitroxides) capable of intramolecular bonding: hydroxyalkyl radical spin adducts of nitrones." Canadian Journal of Chemistry 66, no. 8 (August 1, 1988): 1901–11. http://dx.doi.org/10.1139/v88-307.

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A comparison of the effect of solvent and 13C labeling (of the radical addend) on the EPR (electron paramagnetic resonance) spectra of hydroxyalkyl vs. alkyl radical adducts of α-phenyl-N-tert-butyl nitrone (PBN) and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) has been investigated. The solution ENDOR spectra in toluene and in ethanol are the first examples studied of aminoxyls with hydroxyl substituents in close proximity to the free radical centre. Diastereomeric mixtures of hydroxyalkyl radical adducts are clearly resolved by ENDOR spectroscopy. Conformations of these radicals have been assigned based on the 1H and 13C hyperfine splittings (HFS's) and by differential optimum ENDOR temperatures. Definitive assignments of carbon-centered radical adducts of DMPO and PBN are shown to be feasible by monitoring the β-13C HFS's of the radical addend. Long-range γ-H HFS's from the added radical group can be observed when the deuterated spin trap PBN-d14 is used. The production of 13C labeled hydroxyalkyl adducts of nitrones (e.g., DMPO–13CH2OH, from the reaction of hydroxyl radicals with added 13CH3OH) is shown to be useful as an improved EPR spectroscopic method for the verification of the presence of hydroxyl radicals.

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34

Utenyshev, A. N., and S. M. Aldoshin. "Characteristic features of photochemical conversions ofC-(2-furyl-5-nitro)-N phenyl- andC,N-di(p-bromophenyl)nitrones in liquid and crystal phases." Russian Chemical Bulletin 45, no. 11 (November 1996): 2529–34. http://dx.doi.org/10.1007/bf01431109.

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35

Amutha, Chinnadurai, Sivaperuman Saravanan, and Shanmugam Muthusubramanian. "ChemInform Abstract: Acetic Anhydride Induced Rearrangement and Grignard Addition on C-Phenyl-N-(1-methyl-2-aryl)ethyl Nitrones." ChemInform 44, no. 35 (August 8, 2013): no. http://dx.doi.org/10.1002/chin.201335075.

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36

Gosh, Anindita, Avijit Banerji, and Julie Banerji. "ChemInform Abstract: 1,3-Dipolar Cycloadditions. Part 28. Selective 1,3-Dipolar Cycloadditions of C-Aryl-N-Phenyl Nitrones to Arylidene Acetones." ChemInform 46, no. 17 (April 2015): no. http://dx.doi.org/10.1002/chin.201517181.

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37

Lasri, Jamal, Naser Eltaher Eltayeb, Matti Haukka, and Yousef Alghamdi. "Crystal and molecular structure studies of (Z)-N-methyl-C-4-substituted phenyl nitrones by XRD, DFT, FTIR and NMR methods." Journal of Molecular Structure 1128 (January 2017): 70–78. http://dx.doi.org/10.1016/j.molstruc.2016.08.058.

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38

Chakraborty, Bhaskar, Prawin Kumar Sharma, Neelam Rai, Saurav Kafley, and Manjit Chhetri. "α-N-Methyl/phenyl furan derivatives as dipolarophiles for synthesis of spiro isoxazolidine derivatives with α-chloro and simple nitrones." Journal of Chemical Research 34, no. 3 (March 1, 2010): 147–50. http://dx.doi.org/10.3184/030823410x12675422347141.

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39

Chakraborty, Bhaskar, Prawin Kumar Sharma, Neelam Rai, Saurav Kafley, and Manjit Chhetri. "ChemInform Abstract: α-N-Methyl/Phenyl Furan Derivatives as Dipolarophiles for Synthesis of Spiro Isoxazolidine Derivatives with α-Chloro and Simple Nitrones." ChemInform 41, no. 36 (August 12, 2010): no. http://dx.doi.org/10.1002/chin.201036128.

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40

UTENYSHEV, A. N., and S. M. ALDOSHIN. "ChemInform Abstract: Specific Features of the Photochemical Conversion of C-(5-Nitro-2- furyl)-N-phenyl- and C,N-Di(p-bromophenyl)nitrones in Liquid and Crystal Phases." ChemInform 28, no. 16 (August 4, 2010): no. http://dx.doi.org/10.1002/chin.199716071.

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41

Eskandari, Khalil, Bahador Karami, and Saeed Khodabakhshi. "An Unexpected Catalytic Synthesis of Novel and Known Bis(Pyrazolyl) Methanes by the use of α-aryl-N-phenyl Nitrones in Aqueous Media." Journal of Chemical Research 38, no. 10 (October 2014): 600–603. http://dx.doi.org/10.3184/174751914x14114871789226.

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42

Eskandari, Khalil, Bahador Karami, and Saeed Khodabakhshi. "ChemInform Abstract: An Unexpected Catalytic Synthesis of Novel and Known Bis(pyrazolyl) Methanes by the Use of α-Aryl-N-phenyl Nitrones in Aqueous Media." ChemInform 46, no. 19 (April 23, 2015): no. http://dx.doi.org/10.1002/chin.201519162.

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43

Chakraborty, Bhaskar, and Esmita Chettri. "Synthesis of Some Novel Class of Regioselective Spiro Isoxazolidine Derivatives via 1,3-Dipolar Cycloaddition Reaction of N- Benzyl-C- fluoro-substituted Phenyl Nitrones in Ionic Liquid." Journal of Heterocyclic Chemistry 55, no. 5 (March 12, 2018): 1157–65. http://dx.doi.org/10.1002/jhet.3148.

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44

van Eijk, Peter J. S. S., Willem P. Trompenaars, David N. Reinhoudt, and Sybolt Harkema. "Reaction of four-membered cyclic nitrones with acetyl chlorideα. X-Ray crystal structures of 2-[(acetyloxy)amino]-N,N-diethyl-2-methyl-4-oxo-3-phenylpentanamide and 1-acetyl-3-chloro-N, N-diethyl-2-methyl-4-methylene-3-phenyl-2-azetidinecarboxamide." Recueil des Travaux Chimiques des Pays-Bas 107, no. 2 (September 2, 2010): 52–62. http://dx.doi.org/10.1002/recl.19881070204.

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45

Zhang, Yong-Kang, and Kirk R. Maples. "Synthesis and EPR Evaluation of the Nitrone PBN-[tert-13C] for Spin Trapping Competition." Zeitschrift für Naturforschung B 57, no. 1 (January 1, 2002): 127–32. http://dx.doi.org/10.1515/znb-2002-0116.

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N-[tert-13C]Butyl C-phenyl nitrone (PBN-[tert-13C]) has been synthesized for an EPR spin trapping competition study. The newly synthesized PBN-[tert-13C] shows different 13C-hyperfine splitting constants (a13C) when it traps free radicals as compared to another 13C-labeled PBN analogue, N-tert-butyl C-phenyl [nitronyl-13C]nitrone (PBN-[nitronyl-13C]). The PBN- [tert-13C] hydroxyl adduct gives a larger a13C value (5.14 G) as compared to the PBN-[nitronyl-13C] hydroxyl adduct (4.36 G). This gain ofthe a13C value decreases the chance of EPR signal overlap, thus providing a more resolved EPR spectrum when PBN-[tert-13C] is used as an internal standard for EPR spin trapping competition studies of hydroxyl radical formation.

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46

Rehorek, Detlef, Edward G. Janzen, and Yashige Kotake. "On the spin trapping of chlorine atoms. Competition from chloride ions." Canadian Journal of Chemistry 69, no. 7 (July 1, 1991): 1131–33. http://dx.doi.org/10.1139/v91-167.

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Chlorine atoms generated by photolysis of hexachloroethane add to C-phenyl-N-tert-butyl nitrone (PBN) to form persistent spin adducts that are readily detectable by EPR spectroscopy. The presence of chloride ions reduces spin adduct formation competitively. Chlorine atoms also react with tetraphenylarsenium ions to liberate phenyl radicals by radical replacement. Key words: EPR, spin trapping, C-phenyl-N-tert-butyl nitrone, PBN, photolysis, chlorine atoms, tetraphenylarsenium ion, hexachloroethane.

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47

Bouwman, Jordy, Andras Bodi, and Patrick Hemberger. "Nitrogen matters: the difference between PANH and PAH formation." Physical Chemistry Chemical Physics 20, no. 47 (2018): 29910–17. http://dx.doi.org/10.1039/c8cp05830j.

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Because of the large stability of the nitrile group, the N-substituted aromatic molecule quinoline does not form in the phenyl + acrylonitrile reaction, in contrast to naphthalene formation in the isoelectronic phenyl + vinylacetylene reaction.

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48

Heinemann, Frank W., Helmut Hartung, and Nadja Maier. "Kristall- und Molekülstruktur von 2-[3-(N,N-Diethylammonium)propylimino]-2-phenyl-dithioacetat / Crystal and Molecular Structure of 2-[3-(N,N-Diethylammonium)propylimino]-2-phenyl-dithioacetate." Zeitschrift für Naturforschung B 50, no. 1 (January 1, 1995): 81–85. http://dx.doi.org/10.1515/znb-1995-0116.

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The title compound, formed by the reaction of acetophenone with 3-diethylamino-1-propylamine and sulfur, crystallizes in the orthorhombic space group P212121 (Z = 4) with lattice constants a = 818.1(2) pm, b = 1225.1(2) pm and c = 1622.4(4) pm. The characterization of the molecule as a zwitterion is established by the observed bond parameters. Both spectroscopic investigations and the results of the X-ray structure determination show that a hydrogen atom is bonded to the amino nitrogen rather than to the imino nitrogen.

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49

Lu, Guifen, Xiufeng Zhang, Xu Cai, Yuanyuan Fang, Min Zhu, Weihua Zhu, Zhongping Ou, and Karl M. Kadish. "Synthesis, structural characterization and protonation/deprotonation of hydroxyl-substituted free-base tetraphenylporphyrins in nonaqueous media." Journal of Porphyrins and Phthalocyanines 17, no. 10 (September 9, 2013): 941–53. http://dx.doi.org/10.1142/s1088424613500557.

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A series of hydroxyl-substituted free-base tetraphenylporphyrins was synthesized and characterized by UV-vis spectroscopy, 1 H NMR and mass spectrometry. The porphyrins are represented as (HOPh) n(t BuPh )4-n PH 2, where Ph presents a phenyl group, HO and t Bu are substituents on the para-positions of the phenyl rings of the macrocycle, n = 0–4 and P represents the dianion of tetraphenylporphyrin. The UV-visible properties of each porphyrin were examined in dichloromethane (DCM), N,N′-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) before and after addition of trifluoroacetic acid (TFA) or sodium hydroxide (NaOH) to solution. Equilibrium constants for protonation ( log βn) and deprotonation [Formula: see text] of each compound were determined using standard equations. The protonations occur in a single step involving a simultaneous two proton addition at the porphyrin central nitrogens. The phenolic protons on (HOPh) n(t BuPh )4-n PH 2 are easier to deprotonate than the core nitrogen protons of the porphyrins and this reaction occurs in a single step involving the simultaneous loss of 1–4 protons on the hydroxyl groups followed by a loss of two protons from the central nitrogens. The effect of HO substituents on UV-visible spectra and the magnitude of the protonation/deprotonation constants ( log βn and [Formula: see text]) are discussed. Two of the porphyrins, (t BuPh )4 PH 2 and trans- (HOPh) 2(t BuPh )2 PH 2, are also characterized by a single-crystal X-ray analysis.

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50

Shchepina, Nadezhda E., Viktor V. Avrorin, Gennady A. Badun, Scott B. Lewis, and Sergey N. Shurov. "New Way of Direct Nitrogen Atom Phenylation in Quinoline Derivatives." ISRN Organic Chemistry 2012 (July 3, 2012): 1–4. http://dx.doi.org/10.5402/2012/526867.

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Comparison of ion-molecular reactions of free-phenyl cations generated by tritium β-decay with 2-methyl- and 2-phenylquinolines has been investigated. The reaction of direct nitrogen atom phenylation with the help of nucleogenic phenyl cations has been fulfilled for the first time and a new one-step synthesis of tritium-labeled N-phenyl-2-phenylquinolinium salt—lipophilic radioactive biological marker has been elaborated.

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