Academic literature on the topic 'Grignard-mediated reduction'
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Journal articles on the topic "Grignard-mediated reduction"
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Essa, Ali H., Reinner I. Lerrick, Eçe Çiftçi, Ross W. Harrington, Paul G. Waddell, William Clegg, and Michael J. Hall. "Grignard-mediated reduction of 2,2,2-trichloro-1-arylethanones." Organic & Biomolecular Chemistry 13, no. 20 (2015): 5793–803. http://dx.doi.org/10.1039/c5ob00541h.
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2,2,2-Trichloro-1-aryl-ethanones can be reduced by RMgX to the corresponding 2,2-dichloro-1-arylethen-1-olates and trapped with a range of electrophiles. In addition we demonstrate that 2,2-dichloro-1-arylethen-1-olates undergo counter-ion controlled Darzens condensations.
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Stoner, Eric J., Darlene A. Cothron, Mary K. Balmer, and Brian A. Roden. "Benzylation via Tandem Grignard reaction —iodotrimethylsilane (TMSI) mediated reduction." Tetrahedron 51, no. 41 (October 1995): 11043–62. http://dx.doi.org/10.1016/0040-4020(95)00659-v.
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STONER, E. J., D. A. COTHRON, M. K. BALMER, and B. A. RODEN. "ChemInform Abstract: Benzylation via Tandem Grignard Reaction - Iodotrimethylsilane (TMSI) Mediated Reduction." ChemInform 27, no. 5 (August 12, 2010): no. http://dx.doi.org/10.1002/chin.199605124.
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Le Bailly, Bryden A. F., Mark D. Greenhalgh, and Stephen P. Thomas. "Iron-catalysed, hydride-mediated reductive cross-coupling of vinyl halides and Grignard reagents." Chem. Commun. 48, no. 10 (2012): 1580–82. http://dx.doi.org/10.1039/c1cc14622j.
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Le Bailly, Bryden A. F., Mark D. Greenhalgh, and Stephen P. Thomas. "ChemInform Abstract: Iron-Catalyzed, Hydride-Mediated Reductive Cross-Coupling of Vinyl Halides and Grignard Reagents." ChemInform 43, no. 26 (May 31, 2012): no. http://dx.doi.org/10.1002/chin.201226050.
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Shin, Inji, Stephen D. Ramgren, and Michael J. Krische. "Reductive cyclization of halo-ketones to form 3-hydroxy-2-oxindoles via palladium catalyzed hydrogenation: a hydrogen-mediated Grignard addition." Tetrahedron 71, no. 35 (September 2015): 5776–80. http://dx.doi.org/10.1016/j.tet.2015.05.085.
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Shin, Inji, Stephen D. Ramgren, and Michael J. Krische. "ChemInform Abstract: Reductive Cyclization of Halo-Ketones to Form 3-Hydroxy-2-oxindoles via Palladium Catalyzed Hydrogenation: A Hydrogen-Mediated Grignard Addition." ChemInform 46, no. 48 (November 12, 2015): no. http://dx.doi.org/10.1002/chin.201548128.
Full textDissertations / Theses on the topic "Grignard-mediated reduction"
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Kasprzyk, Milena, and milena kasprzyk@freehills com. "Synthetic Studies Towards the Tridachione Family of Marine Natural Products." Flinders University. Chemistry, Physics and Earth Sciences, 2008. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20081107.085933.
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Since the middle of the 20th century, significant interest has evolved from the scientific community towards the polypropionate family of marine natural products. A number of these compounds have been shown to possess significant biological activity, and this property, as well as their structural complexity, has driven numerous efforts towards their synthesis. The first chapter provides an introduction into the world of polypropionates, with a discussion on synthetic studies into a number of members of the tridachiapyrone family. Fundamental synthetic concepts utilised in this thesis towards the preparation of polyketides are also described, with a focus on their application towards the synthesis of 9,10-deoxytridachione, anti tridachiahydropyrone and syn tridachiahydropyrone.
Chapter 2 describes the work undertaken towards the total synthesis of 9,10-deoxytridachione. The novel tandem conjugate addition-Dieckmann condensation of complex enones developed previously in the Perkins group was used to generate anti methylated cyclohexenones as key synthetic intermediates. The conversion of the cyclohexenones into the corresponding cyclohexadienes via allylic alcohols was attempted, utilising a Grignard-mediated reaction to achieve the selective 1,2-reduction. Studies into the Grignard-mediated reduction were also undertaken on seven additional cyclohexenones, in order to investigate the utility and scope of the reaction.
The extension of the methodology previously developed for the synthesis of cyclohexenones is the subject of Chapter 3. This section describes investigations into the synthesis of stereochemically-diverse cyclohexenones from complex enones. The conjugate addition-Dieckmann condensation strategy was extended successfully towards the synthesis of a syn methylated cyclohexenone, which allowed the synthesis of the proposed true structure of tridachiahydropyrone to be pursued.
The methodology developed in Chapter 3 was utilised in Chapter 4 to synthesise a model system of syn tridachiahydropyrone. A comparative analysis of the NMR data of the syn model, an anti model and anti tridachiahydropyrone with the natural product indicated that the true structure of tridachiahydropyrone may indeed have syn stereochemistry. The synthesis of syn tridachiahydropyrone was attempted, and to this end a suitable cyclohexanone was successfully synthesised. However, the subsequent methylation-elimination cascade failed to furnish the desired syn methylated cyclohexenone, producing only an anti methylated cyclohexanone. The stereochemistry of the methylation was deduced using high and low variable temperature NMR coupled with selective irradiation NOESY.
Book chapters on the topic "Grignard-mediated reduction"
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Taber, Douglass F. "The Nicolaou/Li Synthesis of Tubingensin A." In Organic Synthesis. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190200794.003.0095.
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The complex indole diterpene alkaloids, isolated both from Aspergillus sp. and from Eupenicillium javanicum, display a wide range of physiological activity. K.C. Nicolaou of Scripps/La Jolla and Ang Li, now at the Shanghai Institute of Organic Chemistry, conceived (J. Am. Chem. Soc. 2012, 134, 8078) a divergent strategy for the assembly of these alkaloids that enabled syntheses of both anominine (not illustrated) and tubingensin A 3. A key step in the assembly of the carbocyclic skeleton of both alkaloids was the radical cyclization of 1 to 2, establishing the second of the two alkylated quaternary centers of 3. The starting point for the preparation of 1 was commercial pulegone 4. Methylation followed by acid-mediated retro aldol condensation delivered the enantiomerically pure 2,3-dimethyl cyclohexanone 5. To maximize yield, the subsequent Robinson annulation was carried out over three steps, formation of the silyl enol ether, condensation of the enol ether with methyl vinyl ketone 6, and base-mediated cyclization and dehydration of the 1,5-diketone to give 7. The secondary hydroxyl group was introduced by exposure to Oxone of the methyl dienol ether derived from 7. The mixture of diastereomers from the radical Ueno-Stork cyclization of 1 was equilibrated to the more stable 2 by exposure to acid. The authors took advantage of the regioselective enolization of 2, preparing the silyl enol ether, which could then be condensed with formaldehyde to give 10. This hydroxy ketone was carried onto 11 over four steps, commencing with silylation and proceeding through Wittig condensation, desilylation, and oxidation. The addition of the Grignard reagent 12 to the aldehyde 11 gave a secondary alcohol, which was readily dehydrated to the diene 13. The diene resisted thermal cyclization, but on exposure to CuOTf at room temperature it was smoothly cyclized and oxidized to 14. The elaboration of the sidechain had already been worked out in the anominine synthesis. The free lactol derived from 14 resisted many nucleophiles, but vinyl magnesium bromide did add. Bis acetylation of the resulting diol followed by Pd-mediated ionization and reduction of the allylic acetate, and reductive removal of the residual acetate, delivered the terminal alkene 15. Metathesis with isobutylene gave 16, which was deprotected to give tubingensin A 3.
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Taber, Douglass F. "The Trost Synthesis of (−)-Lasonolide A." In Organic Synthesis. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190646165.003.0093.
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(−)-Lasonolide A 4, isolated from the Caribbean sponge Forcepia sp., showed remarkable anticancer activity in the NIH 60-cell screen. The central step in the synthesis of 4 reported (J. Am. Chem. Soc. 2014, 136, 88) by Barry M. Trost of Stanford University was the remarkably selective, convergent Ru-mediated coupling of 1 with 2 to give 3. To prepare 1, the authors took advantage of the underutilized Cu-mediated addition of a Grignard reagent 6 to propargyl alcohol 5, to give 7. Coupling with the acetonide 8 followed by deprotection led to the phosphonium salt 9. The other half of 1 was prepared from the acetonide 10 of the commodity chemical 1,1,1-tris(hydroxymethyl)ethane. Oxidation followed by Zn-catalyzed aldol addition of the ketone 11 led to the alcohol 12. Diastereoselective reduction followed by protection gave 13. Condensation with benzaldehyde proceeded with remarkable diastereoselection, setting the quaternary center of 14. Spontaneous intramolecular Michael addition proceeded under the conditions of the subsequent Horner-Emmons reaction, leading to the aldehyde 15. Wittig reaction with the phosphonium salt 9 followed by deprotection completed the preparation of the alkyne 1. The β-ketoester 18 prepared by the addition of 17 to 16 was prone to unwanted conjugation, and the terminal alkene was easily reduced under hydrogenation conditions. Enzymatic conditions were found to effect dynamic kinetic resolution and reduction, to give 19. The derived ketone 21, from coupling with 20 was reduced using the Corey organocatalyst, then hydrosilated, leading to 22. Under metathesis with 23, the product unsaturated aldehyde cyclized to 24. Homologation followed by allylation then completed the construction of 2. Acetone was the solvent of choice for the coupling of 1 with 2. This led to the acetonide 3, that was hydrolyzed and protected to give 25. Yamaguchi macrolactonization followed by deprotection then delivered (−)-lasonolide A 4. It is instructive to compare this work to the four previous total syntheses of 4, one of which (Org. Highlights November 26, 2007) we have previously highlighted.
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Taber, Douglass. "Alkaloid Synthesis: Paliurine F, Lepadiformine, and 7-Deoxypancratistatin." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0057.
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The sedative alkaloid paliurine F 7 is a pentapeptide bridged by an arene. Gwilherm Evano of the Université de Versailles took advantage of this in his synthesis (Angew. Chem. Int. Ed. 2007, 46, 572) of 7, although it was necessary to prepare, from serine, one of the amino acid derivatives, the protected 3-hydroxyprolinol 2. The key step in the synthesis was the Cu-catalyzed intramolecular coupling of 5 to give the macrolactam 6. Deprotection and acylation then gave paliurine F 7. Lepadiformine 14, isolated from the tunicate Clavelina lepadiformis, shows moderate cytotoxicity, and is also a K+ channel blocker. The synthesis of 14 (Angew. Chem. Int. Ed. 2007, 46, 2631) by Donald Craig of Imperial College started with the aziridine 8, prepared from the corresponding epoxide. Opening of the protected aziridine with the anion of methyl phenyl sulfone set the stage for condensation of the dianion derived from 9 with the aldehyde 10, to give, with high diastereocontrol, the amine 11. Deprotection followed by cyclization then led to the activated ether 12. While the opening of 12 with an alkyl Grignard reagent proceeded with undesired inversion at the reacting center, opening with the alkynyl Grignard delivered mainly the desired 13. Reduction followed by oxidation, epimerization and reduction then gave lepadiformine 14. The Amaryllidaceae alkaloid 7-deoxypancratistatin 21 has potent antiviral activity. A challenge in the assembly of 21 is that the ring fusion is trans, less stable than the corresponding cis diastereomer. The synthesis of 21 (J. Org. Chem. 2007, 72, 2570) by Albert Padwa of Emory University started with 17, the preparation of which by the combination 15 and 16 he had previously reported in the course of his synthesis of lycoricidine (OHL December 11, 2006). Ester 17 had the desired trans ring fusion, but with an angular ester substituent that had to be removed. While it would be expected from the mechanism that Rh-mediated decarbonylation of an aldehyde would proceed with retention of absolute configuration, and this had been confirmed experimentally, this reaction had not been applied to such a challenging substrate. In the event, the transformation proceeded smoothly, to give the desired trans 19. Dehydration and dihydroxylation of 19 led to the cyclic sulfate 20, selective SN2 opening of which delivered 7-deoxypancratistatin 21.
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Taber, Douglass F. "The Tanino/Miyashita Synthesis of Solanoeclepin A." In Organic Synthesis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199965724.003.0104.
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Building on the Tanino synthesis of glycinoeclepin (Organic Highlights, January 3, 2011), the hatch-stimulating substance for the soybean cyst nematode, Keiji Tanino of Hokkaido University and Masaaki Miyashita, now at Kogakuin University, described (Nat. Chem. 2011, 3, 484) a convergent synthesis of solanoeclepin A 3, the hatch-stimulating substance for the potato cyst nematode. A key step in the synthesis was the diastereoselective Diels-Alder cyclization of 1 to 2. The starting point for the synthesis was the conjugate addition of 5 to 3-methyl cyclohexenone 4, followed by aldol condensation. The secondary acetate corresponding to 6 was readily resolved by lipase hydrolysis. The next challenge was the installation of the angular vinyl group. Enone transposition gave 7, to which vinyl Grignard added with high diastereocontrol, leading to the diol 8. TMSOTf-mediated epoxide rearrangement with concomitant 1,2 vinyl shift then delivered 9. Epoxidation followed by Stork cyclization completed the construction of the cyclobutane 10. The allylic alcohol 12 was enantiomerically pure, so the relative configuration of the sidechain cyclopropane could be set by the Charette protocol. Grieco dehydration of 14 then gave 16, a latent form of the cyclobutanone of 3. Condensation of the ketone 17 with 18 delivered the expected keto enamine, which rearranged nicely on exposure to Tf2O to the aldehyde 19. Diastereoselective addition of the furyl lithium 20 followed by Pd-catalyzed coupling with 21 then completed the assembly of the Diels-Alder substrate 1. The Me2AlCl-mediated intramolecular Diels-Alder cyclization of 1 led to 2 with remarkable diastereocontrol. Oxidation gave 22, that was further oxidized to the protected enol 23. Reduction, alkene cleavage, and protecting group manipulation then set the stage for the final oxidation of 24 to solanoeclepin A 3.
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Taber, Douglass. "Enantioselective Construction of Alkylated Centers." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0039.
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Unsaturated half acid esters such as 1 are readily prepared by Stobbe condensation between dialkyl succinate and an aldehyde. Johannes G. de Vries of DSM and Floris P. J. T. Rutjes of Radboud University Nijmegen observed (Adv. Synth. Catal. 2008, 350, 85) that these acids were excellent substrates for enantioselective hydrogenation. Kazuaki Kudo of the University of Tokyo designed (Organic Lett. 2008, 10, 2035) a resin bound peptide catalyst for the transfer reduction of unsaturated aldehydes such as 3 , using 4 as the net H2 donor. Note that 5 was produced with high enantiocontrol from 3 that was a ~ 2:1 mixture of geometric isomers. Motomu Kanai and Masakatsu Shibasaki of the University of Tokyo devised (J. Am. Chem. Soc. 2008, 130, 6072) a chiral Gd catalyst that mediated the conjugate cyanation of enones such as 6 with high ee. Eric N. Jacobsen of Harvard University prepared (Angew. Chem. Int. Ed. 2008, 47, 1762) a dimeric Al salen catalyst that showed improved activity over the monomeric catalysts. Even congested imides such as 8 could be cyanated efficiently, delivering alkylated quaternary stereogenic centers. Takahiro Nishimura and Tamio Hayashi of Kyoto University optimized (J. Am. Chem. Soc. 2008, 130, 1576) the Rh*-catalyzed enantioselective conjugate addition of silyl acetylenes to enones such as 10, to give 12. Adriaan J. Minnaard and Ben L. Feringa of the University of Groningen devised (Angew. Chem. Int. Ed. 2008, 47, 398) conditions for the enantioselective 1,6-conjugate addition of alkyl Grignard reagents to diene esters such as the inexpensive ethyl sorbate 14. The product 16 incorporated, in addition to the newly formed stereogenic center, a geometrically defined E alkene. William S. Bechara and André B. Charette of the Université de Montréal found (Organic Lett. 2008, 10, 2315) that alkyl Grignard reagents could be induced to add with high enantioselectivity to pyridyl sulfones such as 17. In a different approach, Gregory C. Fu of MIT developed (J. Am. Chem. Soc. 2008, 130, 3302; J. Am. Chem. Soc. 2008, 130, 2756) conditions for the enantioselective alkenylation of racemic bromo esters such as 19, The latter reference is to the analogous enantioselective coupling of organozinc bromides with racemic allylic chlorides.
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Taber, Douglass F. "New Methods for C-C Bond Construction." In Organic Synthesis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199965724.003.0023.
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Luigino Troisi of the University of Salento found (Tetrahedron Lett. 2010, 51, 371) that a variety of primary and secondary amines could be coupled with a benzylic halide 1 under carbonylating conditions. Ilhyong Ryu of Osaka Prefecture University showed (Organic Lett. 2010, 12, 1548) that under reducing conditions, an iodide 3 coupled with CO to give the primary alcohol. Felicia A. Etzkorn of Virginia Tech observed (Organic Lett. 2010, 12, 696) that under Hg hydrolysis conditions, the orthothioester derived from 5 coupled with 6 to give 7. Yasuharu Yoshimi of the University of Fukui and Minoru Hatanaka of Iwate Medical University devised (Tetrahedron Lett. 2010, 51, 2332) conditions for the decarboxylative addition of the acid 8 to 9 to give 10. Yong-Min Liang and Xiaojun Yao of Lanzhou University and Chao-Jun Li of McGill University described (J. Org. Chem. 2010, 75, 783) a related procedure with α-amino acids. Yasutaka Ishii of Kansai University established (J. Am. Chem. Soc. 2010, 132, 2536) that t -butyl acetate 12 was an effective partner for the Ir-mediated oxidation-coupling-reduction of an alcohol 11. He used (J. Org. Chem. 2010, 75, 1803) a similar protocol to condense acetone with the diol 14, to give the long-chain diketone 16. The formation of allylic Grignard reagents can be inefficient because the excess reactive halide tends to couple with the Grignard reagent as it forms. Brandon L. Ashfeld of the University of Notre Dame found (Tetrahedron Lett. 2010, 51, 2427) a simple solution to this problem: inclusion of a catalytic amount of the inexpensive Cp2 TiCl2 to mediate the addition of 18 to 17. Brian T. Connell of Texas A&M University demonstrated (J. Am. Chem. Soc. 2010, 132, 7826) that with Mn, 21 could be added to 20. The acetate 21 is thus an easily prepared homoenolate equivalent. Note that although 21 is an E/Z mixture, the product 22 is cleanly Z. Gérard Cahiez of the Université de Paris 13 reported (Synlett 2010, 299) a detailed study of the Cu-catalyzed coupling of 24 with 23. Without supporting ligands, slow addition (syringe pump, 1 h) of 24 to 23 assured clean formation of 25. Manual slow addition (dropping funnel, 15 min) was not effective.
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Taber, Douglass. "Enantioselective Construction of Alkylated Stereogenic Centers." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0038.
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The enantioselectivity of alkene reduction usually depends on the geometric purity of the alkene. Bruce H. Lipshutz of the University of California, Santa Barbara used ( Organic Lett. 2007, 9, 4713) carboalumination of the alkyne 1 to prepare 2, which was selectively reduced to 3 in high ee. André B. Charette of the Université de Montréal reported ( Angew. Chem. Int. Ed. 2007, 46, 5955) a related reduction of unsaturated sulfones such as 4. Juan C. Carretero of the Universidad Autónoma de Madrid has developed ( J. Org. Chem. 2007, 72, 9924) a complementary route to enantiomerically-enriched sulfones, by conjugate addition to the unsaturated pyridyl sulfone 6 . Specifically for styrene derivatives, Hans-Günther Schmalz of the University of Cologne has shown (Organic Lett. 2007, 9, 3555) that the product 11 from enantioselective Rh-catalyzed hydroboration can be homologated to 13. Conjugate addition of stabilized carbanions can also be carried out with high enantiocontrol. David A. Evans of Harvard University has described (J. Am. Chem. Soc. 2007, 129, 11583) the Ni-catalyzed addition of malonate 15 to nitroalkenes such as 14. Claudio Palomo of the Universidad de País Vasco (Angew. Chem. Int. Ed. 2007, 46, 8431) and concurrently Yujiro Hayashi of the Tokyo University of Science (Organic Lett. 2007, 9, 5307) have developed organocatalytic protocols for the addition of nitromethane 18 to unsaturated aldehydes such as 17. J. Michael Chong of the University of Waterloo has found (J. Am. Chem. Soc. 2007, 129, 4908) that the Binol-mediated enantioselective conjugate addition of alkenylboronic acids such as 22 required the additional activation of the aryl ketone. Shun-Jun Li of Suzhou University and Teck-Peng Loh of Nanyang Technical University have extended (J. Am. Chem. Soc. 2007, 129, 276) enantioselective conjugate to unsaturated esters such as 24 to more highly substituted Grignard reagents. Alexandre Alexakis of the University of Geneva has demonstrated (Tetrahedron Lett. 2007, 48, 7408) that Ac2O is compatible with Et2 Zn conjugate addition conditions, leading directly to the trapped enolate 27. Selective cleavage of 27 can then be used to prepare acyclic derivatives.
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Taber, Douglass. "The Betzer and Ardisson Synthesis of (+)-Discodermolide." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0085.
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( + )-Discodermolide 3, a potent anticancer agent that works synergistically with taxol, may yet prove to be clinically effective. For the synthetic material to be affordable, a highly convergent synthesis is required. Jean-François Betzer and Janick Ardisson of the Université de Cergy- Pontoise have described (Angew. Chem. Int. Ed. 2007, 46, 1917) such a synthesis, coupling 1 and 2. A central feature of their approach was the repeated application of the inherently chiral secondary organometallic reagent 5. The first use of 5 was the addition to the aldehyde 4. The product 6 was ozonized, and the resulting aldehyde was carried on to the α, β-unsaturated ester. Exposure of the hydroxy ester to benzaldehyde under basic conditions delivered, by intramolecular Michael addition, the acetal 7. The next addition of the reagent 5 was to the aldehyde 10. The adduct 11 was deprotonated with t-BuLi to effect α-elimination, providing, after protection of the alcohol, the alkyne 12. Coupling of 12 with the amide 7 gave a ketone, enantioselective reduction of which under Itsuno-Corey conditions led, again after protection of the alcohol, to the alkyne 13. Oxidation followed by selective hydrogenation and iodine-tin exchange then completed the assembly of 1. Note that PtO2, not typically used for partial hydrogenation, was the catalyst of choice for this congested alkyne. The third application of the enantiomerically-pure reagent 5 was addition to the aldehyde that had been prepared by ozonolysis of 15. Advantage was then taken of another property of the alkenyl carbamate, Ni-mediated Grignard coupling, to form the next carbon-carbon bond with high geometric control. Deprotection of the diene 17 so prepared followed by iodination then completed the synthesis of 2. The convergent coupling of 1 with 2 was carried out under Suzuki conditions. Reduction of the iodide of 2 to the corresponding alkyl lithium followed by exchange with B-OMe-9-BBN gave an intermediate organoborane, that smoothly coupled with 1 under Pd catalysis to give 18.
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Taber, Douglass F. "The Dixon Synthesis of Manzamine A." In Organic Synthesis. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190200794.003.0100.
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The pentacyclic alkaloid manzamine A 4, isolated from a sponge collected in the Okinawa Sea, displays a range of antibacterial, anticancer, and antimalarial activity. The preparation of 4 reported (J. Am. Chem. Soc. 2012, 134, 17482) by Darren J. Dixon of the University of Oxford showcases the versatility of the nitro group in organic synthesis. The nitro alkene 2 was prepared from the commercial bromide 5. Displacement with acetate followed by Swern oxidation led to the aldehyde 6, which was condensed with nitromethane to give 2. Lactam 1 was an intermediate in Professor Dixon’s synthesis (Org. Highlights May 3, 2010) of (–)-nakadomarin A. Lactam 1 was prepared from the tosylate 7, which was derived from pyroglutamic acid. The addition of 1 to the nitroalkene 2 delivered 3 as the dominant diastereomer of the four that were possible. Mannich condensation with formaldehyde and the amine 12 gave 13. The nitro group of 13 was removed by free radical reduction. Exposure of the reduced product to trimethylsilyl iodide gave, via ionization of the ketal, the primary iodide, which was carried onto the nitro compound 14. Dibal selectively reduced the δ-lactam. Partial reduction of the γ-lactam then gave an intermediate that engaged in Mannich condensation with the nitro-activated methylene to give 15. Although there are many protocols for the conversion of a nitro compound to a ketone, most of those were not compatible with the functional groups of 15. Fortunately, Ti(III) was effective. Ce-mediated addition of the Grignard reagent 16 to the ketone followed by deprotection and protection then delivered the silyl ether 17. Remarkably, the ketone 17 could be deprotonated and carried on to the enol triflate 18 without eliminating the TMSO group. Coupling with the stannane 19 then completed the synthesis of manzamine A 4. One-carbon homologation of 18 led to ircinol A, ircinal A, and methyl ircinate (not illustrated).
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Taber, Douglass. "New Methods for Carbon-Carbon Bond Construction." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0017.
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Mohammad Navid Soltani Rad of Shiraz University of Technology has shown (Tetrahedron Lett. 2007, 48, 6779) that with tosylimidazole (TsIm) activation in the presence of NaCN, primary, secondary and tertiary alcohols are converted into the corresponding nitriles. Gregory C. Fu of MIT has devised (J. Am. Chem. Soc. 2007, 129, 9602) a Ni catalyst that mediated the coupling of sp3-hybridized halides such as 3 with sp3-hybridized organoboranes such as 4, to give 5. Usually, carbanions with good leaving groups in the beta position do not couple efficiently, but just eliminate. Scott D. Rychnovsky of the University of California, Irvine has found (Organic Lett . 2007, 9, 4757) that initial protection of 6 as the alkoxide allowed smooth reduction of the sulfide and addition of the derived alkyl lithium to the amide 7 to give 8. Doubly-activated Michael acceptors such as 11 are often too unstable to isolate. J. S. Yadav of the Indian Institute of Chemical Technology, Hyderabad has shown (Tetrahedron Lett. 2007, 48, 7546) that Baylis-Hillman adducts such as 9 can be oxidized in situ, with concomitant Sakurai addition to give 12. Rather than use the usual Li or Na or K enolate, Don M. Coltart of Duke University has found (Organic Lett. 2007, 9, 4139) that ketones such as 13 will condense with amides such as 14 to give the diketone 15 on exposure to MgBr2. OEt2 and i -Pr2 NEt. Simultaneously, Gérard Cahiez of the Université de Cergy (Organic Lett. 2007, 9, 3253) and Janine Cossy of ESPCI Paris (Angew. Chem. Int. Ed. 2007, 46, 6521) reported that Fe salts will catalyze the coupling of sp2 -hybridized Grignard reagents such as 17 with alkyl halides. John Montgomery of the University of Michigan has described (J. Am. Chem. Soc. 2007, 129, 9568) the Ni-mediated regio- and enantioselective addition of an alkynes 20 to an aldehyde 19 to give the allylic alcohol 21. In a third example of sp2 - sp3 coupling, Troels Skrydstrup of the University of Aarhus has established (J. Org. Chem. 2007, 72, 6464) that Negishi coupling with alkenyl phosponates such as 23 proceeded efficiently.