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Bibliografias temáticas / Regioselective reduction

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Literatura científica selecionada sobre o tema "Regioselective reduction"

Autor: Grafiati

Publicado: 23 de novembro de 2024

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Artigos de revistas sobre o assunto "Regioselective reduction"

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Butler, Christopher R., Justin Bendesky e Allen Milton Schoffstall. "Regioselective Reduction of 1H-1,2,3-Triazole Diesters". Molecules 26, n.º 18 (15 de setembro de 2021): 5589. http://dx.doi.org/10.3390/molecules26185589.

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Regioselective reactions can play pivotal roles in synthetic organic chemistry. The reduction of several 1-substituted 1,2,3-triazole 4,5-diesters by sodium borohydride has been found to be regioselective, with the C(5) ester groups being more reactive towards reduction than the C(4) ester groups. The amount of sodium borohydride and reaction time required for reduction varied greatly depending on the N(1)-substituent. The presence of a β-hydroxyl group on the N(1)-substituent was seen to have a rate enhancing effect on the reduction of the C(5) ester group. The regioselective reduction was attributed to the lower electron densities of the C(5) and the C(5) ester carbonyl carbon of the 1,2,3-triazole, which were further lowered in cases involving intramolecular hydrogen bonding.

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Hussaini, Syed Raziullah, e Mark G. Moloney. "Regioselective Reduction of β‐Enaminoesters". Synthetic Communications 35, n.º 8 (1 de abril de 2005): 1129–34. http://dx.doi.org/10.1081/scc-200054223.

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Hirota, Kosaku, Hironao Sajiki, Ryuji Hattori, Yasunari Monguchi, Genzoh Tanabe e Osamu Muraoka. "Regioselective BH3–hydride reduction of inosine derivatives". Tetrahedron Letters 43, n.º 4 (janeiro de 2002): 653–55. http://dx.doi.org/10.1016/s0040-4039(01)02209-2.

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Bruhn, Torsten, e Christian Brückner. "Origin of the Regioselective Reduction of Chlorins". Journal of Organic Chemistry 80, n.º 10 (6 de março de 2015): 4861–68. http://dx.doi.org/10.1021/acs.joc.5b00137.

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Setamdideh, Davood, e Behzad Zeynizadeh. "Mild and Convenient Method for Reduction of Carbonyl Compounds with the NaBH4/Charcoal System in Wet THF". Zeitschrift für Naturforschung B 61, n.º 10 (1 de outubro de 2006): 1275–81. http://dx.doi.org/10.1515/znb-2006-1014.

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The NaBH4/C (charcoal) system reduces a variety of carbonyl compounds such as aldehydes, ketones, acyloins and α-diketones to their corresponding alcohols in high to excellent yields. Reduction reactions were carried out in wet THF at r. t. In addition, regioselective 1,2-reduction of α,β - unsaturated aldehydes and ketones was achieved perfectly with this reducing system. By decreasing the amount of aprotic solvent, all reductions took place fast and efficiently under solid-gel condition

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Katagiri, Takayuki, e Yutaka Amao. "Visible light driven selective NADH regeneration using a system of water-soluble zinc porphyrin and homogeneous polymer-dispersed rhodium nanoparticles". New Journal of Chemistry 45, n.º 35 (2021): 15748–52. http://dx.doi.org/10.1039/d1nj02856a.

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We discovered the catalytic activity of Rh nanoparticles dispersed by polyvinylpyrrolidone for regioselective NAD+ reduction to 1,4-NADH. Only 1,4-NADH was produced as the reduction product of NAD+ with visible-light irradiation.

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Nguyen, Mai, Issam Kherbouche, Sarra Gam-Derouich, Iman Ragheb, Stéphanie Lau-Truong, Aazdine Lamouri, Georges Lévi et al. "Regioselective surface functionalization of lithographically designed gold nanorods by plasmon-mediated reduction of aryl diazonium salts". Chem. Commun. 53, n.º 82 (2017): 11364–67. http://dx.doi.org/10.1039/c7cc05974d.

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Ishii, Hideki, Sergei V. Dzyuba e Koji Nakanishi. "Lactone-free ginkgolides via regioselective DIBAL-H reduction". Organic & Biomolecular Chemistry 3, n.º 19 (2005): 3471. http://dx.doi.org/10.1039/b509129b.

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Davey, C. "Regioselective reduction of substituted dinitroarenes using baker's yeast". Tetrahedron Letters 35, n.º 41 (10 de outubro de 1994): 7867–70. http://dx.doi.org/10.1016/s0040-4039(00)77393-x.

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Davey, Claire L., Lawson W. Powell, Nicholas J. Turner e Andrew Wells. "Regioselective reduction of substituted dinitroarenes using baker's yeast". Tetrahedron Letters 35, n.º 42 (outubro de 1994): 7867–70. http://dx.doi.org/10.1016/0040-4039(94)80139-8.

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Teses / dissertações sobre o assunto "Regioselective reduction"

1

Hassan, Hassan Abbas. "Partial synthesis and regioselective reduction of steroidal 11,12-seco-dioic anhydrides". Thesis, University of Glasgow, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281225.

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Fox, Stephen Carter. "Regioselective Synthesis of Novel Cellulose Derivatives for Drug Delivery". Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/77263.

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New methods were developed for the regioselective synthesis of new classes of cellulose derivatives with properties that could help improve the delivery of pharmaceutical drugs within the human body. The specific synthetic targets of this research were regioselectively carboxylated and regioselectively aminated cellulose derivatives. While different avenues to the carboxylated cellulose were ultimately explored without success, a new method for the synthesis of selectively O-acylated 6-amino-6-deoxy-cellulose esters was devised. A key reaction that enabled the synthesis of the new cellulose derivatives described in this dissertation was the one-pot conversion of microcrystalline cellulose to 6-bromo-6-deoxy-cellulose esters. This reaction resulted in the highly selective displacement of the primary hydroxyl groups attached to the 6-carbon (C-6) on each anhydroglucose unit (AGU) in cellulose with bromide, with little or no bromination occurring at carbons 2 and 3 (C-2 and C-3). The brominated cellulose was then completely esterified by adding acetic, propionoic, or butyric acid anhydride to the reaction solution. The reaction products were readily soluble in many common organic solvents, including acetone, dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, and chloroform. It was shown that the bromides could be converted to iodides under Finkelstein reaction conditions. The presence of halides at C-6 allows a variety of new functional groups to be regioselectively introduced to cellulose via nucleophilic substitution. In one case, the 6-bromo-6-deoxy-cellulose esters were reacted with sodium cyanide to produce regioselectively synthesized cellulose nitriles. These compounds were synthesized with the idea that they could be converted to regioselectively carboxylated cellulose derivatives as an alternative pathway to the rhodium-catalyzed carbonyl insertion reactions also attempted in this research. However, the cellulose nitriles were highly susceptible to alkaline degradation, and conversion to the carboxylated cellulose was not achieved. The 6-bromo-6-deoxy-cellulose esters were also reacted with sodium azide to successfully produce 6-azido-6-deoxy-cellulose esters. The azide groups were then reduced to amines using the Staudinger reaction. This very mild and selective reaction allowed the conversion of the azides to amines in the presence of the ester groups still attached to the cellulose backbone. Such derivatives could have properties useful for a range of biomedical applications, including the delivery of anionic drugs.
Ph. D.

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Arnaout, Abdulkarim al. "Synthese regioselective de dihydropyridines et de pyridines 2- ou 4-fonctionnalisees : applications". Poitiers, 1987. http://www.theses.fr/1987POIT2254.

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4

Rodrigo, Sanjeewa K. "Nickel Catalyzed Regioselective Reductive Coupling Reactions". University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1396532622.

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5

Ma, Zhiwei. "Progress Towards the Total Synthesis of Yaku'amide A". BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/6002.

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The synthetic progress towards yaku'amide A is described. The study leads to development of new synthetic methodologies. Base-free regioselective aminohydroxylation is convenient to deliver β-tert-hydroxyamino acids. A sequence consisting of alkylative esterification, Martin sulfurane mediated anti dehydration, a tandem azide reduction-O→N acyl transfer allows the rapid access of E- and Z-dehydroisoleucine-containing peptides from β-tert-hydroxyisoleucine derivatives. Those methods are effective in constructing complicated peptides and advanced subunits of yaku'amide A.

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6

BOUTOUTE, PATRICK. "Reductions electrochimique et electroenzymatique regioselectives ou enantiogenique de systemes insaturees". Clermont-Ferrand 2, 1995. http://www.theses.fr/1995CLF21710.

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Ce travail presente les differents resultats obtenus dans l'etude de la reduction purement electrochimique ou electroenzymatique de molecules presentant une ou plusieurs insaturations. Ainsi, differentes 2-aroyl et 2-acetylchromones ont ete etudiees en vue de leur reduction regioselective. Il a ete montre que dans le cas des 2-aroylchromones, la fonction carbonyle du substituant en position 2 du cycle chromone a ete reduite regioselectivement tandis que pour la 2-acetylchromone, c'est la double liaison du cycle qui est reduite. Les produits obtenus conduisent apres une nouvelle electroreduction a des dimeres extremement instables. Un phenomene d'autoprotonation a ete observe avec les chromones substituees par des fonctions phenol ou chlorhydrate d'amine. La reduction enzymatique d'-ceto-carboxylates par proteus mirabilis avec regeneration electrochimique du systeme enzyme-cofacteur par un mediateur (viologene) a conduit a des -hydroxyacides de configuration (r) avec d'excellents exces enantiomeriques. Le choix de la solution tampon et l'influence d'additions de tensioactifs ont ete discutes. Dans le cas d'un cetocarboxylate racemique, l'electrochimie a permis de mettre en evidence une enantioselectivite des reductases vis-a-vis du substrat par le suivi de l'intensite du courant d'electrolyse. L'etude electrochimique d'-dicetones a mis en evidence une certaine regioselectivite dans la reduction de diones dissymetriques en particulier dans le cas de la 1-phenylpropane-1,2-dione pour laquelle seule la fonction carbonyle en du groupement phenyle est reduite. La reduction microbiologique de ces diones toujours par proteus mirabilis a conduit a un unique cetol de configuration (2s) avec une tres bonne purete optique pour les 2,3-diones et la 1-phenylpropane-1,2-dione. La reduction electroenzymatique de ces composes n'a pas donne de bons resultats, les differentes molecules etudiees se reduisant a un potentiel trop proche de celui des mediateurs utilises. Differentes techniques d'analyses (rmn, point de fusion, microanalyses, pouvoir rotatoire, chromatographie en phase vapeur sur colonne chirale ou non chirale, rpe, ir), ont permis d'identifier et de caracteriser les produits obtenus

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7

Palucci, Benedetta. "Rhodium and Palladium Catalysed Unusual Regioselective Hydroformylation and Rhodium Catalysed Reductive Carbonylation". Doctoral thesis, Universitat Rovira i Virgili, 2020. http://hdl.handle.net/10803/670491.

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La present tesi doctoral té com a objectiu el desenvolupament de sistemes per aconseguir una regioselectivitat no convencional en l’hidroformilació d'alquens terminals. Degut a que nombroses substàncies naturals perfumades contenen un grup aldehid. Els processos d’hidroformilació, on es fan reaccionar monòxid de carboni i hidrogen amb olefines, han esdevenit mètodes inestimables per a les empreses de fragàncies per a la producció d’aquests derivats. La regioselectividad del procés, per a l’obtenció del producte lineal o ramificat, és extremadament dependent del substrat. Com a tendència general en l’hidroformilació catalitzada per Rh, els alquens terminals, com l’1-octè, reaccionen per a la producció d’aldehids lineals, mentre que els alquens vinílic, com l’estirè, proporcionen els productes ramificats corresponents. No obstant, per a la síntesis de noves substàncies perfumades, l’accés als aldehids oposats seria sens dubte beneficiós. Al Capítol 3 es descriu la síntesis de nous lligands bidentats centrats en fòsfor i nitrogen i la seva aplicació en l’hidroformilació de 1-hexè catalitzada per rodi, obtenint el producte ramificat. Al Capítol 4 s’aporta la síntesi d’una nova família de lligands fosfina-fosfit i fosfina-fosforamidit i la seva aplicació en l’hidroformilación de l’1-octè cap a l’aldehid ramificat, catalitzada per rodi. El Capítol 5 es centra en la hidroformilació d’estirè catalitzada per rodi amb lligands bis (dipirrolil-fosforamidit), cap a la producció del producte lineal. El Capítol 6 ofereix el desenvolupament d'un procés sense precedents anomenat "carbonilació reductora catalitzada per rodi" de l'acetat al·lílic, per a la producció de l'aldehid corresponent. A més d’un estudi de la reactivitat del sistema catalític mitjançant RMN d'alta pressió. Finalment, al Capítol 7 es presenten els resultats obtinguts en l’hidroformilació d’estirè catalitzada per pal·ladi, utilitzant formaldehid com a substitut de gas de síntesi.
La presente tesis doctoral tiene como objetivo el desarrollo de sistemas para la obtención de regioselectividad no convencional en la hidroformilación de alquenos terminales. Debido a que numerosas sustancias naturales perfumadas contienen un grupo aldehído. Los procesos de hidroformilación, en los cuales monóxido de carbono e hidrógeno son añadidos a las olefinas, se han convertido en métodos invaluables para la producción de estos derivados en empresas de fragancias. La regioselectividad del proceso, en el cual se obtiene el producto lineal o ramificado, depende en gran medida del sustrato. Como tendencia general en la hidroformilación catalizada por Rh, los alquenos terminales, como por ejemplo el 1-octeno, reaccionan para producir aldehídos lineales mientras que los alquenos vinílicos, como el estireno, forman los correspondientes productos ramificados como productos favorecidos. Sin embargo, para la síntesis de nuevas sustancias perfumadas sería beneficioso el acceso a los aldehídos contrarios. En el Capítulo 3 se describe la síntesis de nuevos ligandos bidentados centrados en nitrógeno y fósforo y su aplicación en la hidroformilación catalizada por rodio de 1-hexeno hacia el producto ramificado. En el Capítulo 4 se aporta la síntesis de una nueva familia de ligandos fosfina-fosfito y fosfina-fosforamidita y su aplicación en la hidroformilación de 1-octeno catalizada por rodio, formando el aldehído ramificado. El Capítulo 5 se centra en la hidroformilación de estireno catalizada por rodio con ligandos de bis (dipirrolilfosforamidita), en este caso, hacia la obtención del producto lineal. El Capítulo 6 presenta el desarrollo de un proceso sin precedentes denominado “carbonilación reductora catalizada por rodio” del acetato alílico, para la producción del aldehído correspondiente. Además de un estudio de la reactividad del sistema catalítico mediante RMN de alta presión. Finalmente, el Capítulo 7 ofrece los resultados obtenidos en la hidroformilación de estireno catalizada por paladio, utilizando en este caso formaldehído como sustituto del gas de síntesis.
The current Ph.D. Thesis deals with the development of systems for achieving unconventional regioselectivity in the hydrofomylation of terminal alkenes. Numerous scented natural substances contain an aldehyde group. As such, hydroformylation processes, where carbon monoxide and hydrogen are added onto olefins, have become invaluable methods for the fragrance companies to produce these derivatives. The regioselectivity between linear and branched product of the process is extremely substrate dependent. As a general trend, terminal alkenes, such as 1-octene, react to yield linear aldehydes while vinyl arenes, such as styrene, afford the corresponding branched products, as favoured products in Rh-catalysed hydroformylation. However, to synthetise new scented substances, accessing the opposite aldehydes would be undoubtedly beneficial. In Chapter 3 the application of newly synthetised bidentate phosphorus-nitrogen-centred ligands in the rhodium catalysed hydroformylation of 1-hexene towards the branched product, is described. In Chapter 4 is reported a novel family of phosphine-phosphite and phosphine-phosphoramidite ligands and their application in the rhodium catalysed hydroformylation of 1-octene, towards the branched aldehyde. Chapter 5 is focused on the rhodium catalysed hydroformylation of styrene with bis(dipyrrolyl-phosphoramidite) ligands, towards the production of linear product. Chapter 6 deals with the development of an unprecedent process so called “rhodium catalysed reductive carbonylation” of allylic acetate to produce the corresponding aldehyde. Furthermore, the results obtained via high pressure NMR in the study of the reactivity of the catalytic system are described. Finally, Chapter 7 presents the results obtained in the palladium catalysed hydroformylation of styrene, using formaldehyde as syngas surrogates.

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Gommenginger, Clément. "Des ynamides pour la synthèse de molécules azotées fluorées inédites". Electronic Thesis or Diss., Strasbourg, 2024. http://www.theses.fr/2024STRAF024.

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Ces travaux décrivent l’utilisation d’ynamides et de N-allènamides comme intermédiaires clés pour la synthèse d’hétérocycles azotés et fluorés inédits. Une réaction de cyclisation intramoléculaire de mésyl N-allènamides trifluorométhylés promue par le TBAF a permis la synthèse de y-sultames trifluorométhylés alors que, l’utilisation d’un mélange TBAF/acide acétique, a permis l’obtention de y-sultames gem-difluorés. La formation de diènes trifluorométhylés substitués par une fonction amide, obtenue par une réaction de métathèse d’ène-ynamides avec un aldéhyde, a permis la synthèse de plateformes moléculaires hautement fonctionnalisées. Le traitement de ces diènes par des amines primaires, a permis l’obtention stéréosélective de y-lactames trifluorométhylés à l’aide d’un processus domino d’hydroamination/isomérisation/transamidation. Enfin, la réduction régio- et stéréosélective de chaque double liaison des N-allènamides trifluorométhylés a été explorée. Des allylamides ont été obtenus par réduction de la partie énamide des N-allènamides, alors que des énamides ont été formés par isomérisation, en milieu basique des allylamides
This work describes the use of ynamides and N-allenamides as key intermediates for the synthesis of novel nitrogen and fluorine containing heterocycles. A TBAF-promoted intramolecular cyclization reaction of trifluoromethylated mesyl N-allenamides led to the synthesis of trifluoromethylated y-sultams, while the use of a TBAF/acetic acid mixture afforded gem-difluorinated y-sultams. The formation of amide-substituted trifluoromethylated dienes, obtained through metathesis of ene-ynamides with an aldehyde, enabled the synthesis of highly functionalized molecular platforms. Treatment of these dienes with primary amines enabled the stereoselective production of trifluoromethylated y-lactams via a domino hydroamination/isomerization/transamidation process. Finally, the regio- and stereoselective reduction of each double bond of trifluoromethylated N-allenamides was explored. Allylamides were obtained by reduction of the enamide part of N-allenamides, while enamides were formed by isomerization, in basic medium of allylamides

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Sayah, Ghassemi Babak. "Chimie et réactivité des hexahydropyrroloindolizines : application à la synthèse des myrmicarines". Université Joseph Fourier (Grenoble), 2001. http://www.theses.fr/2001GRE10114.

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Parmi les composes naturels ou synthetiques possedant des activites biologiques interessantes, les alcaloides tiennent une part importante. Recemment une nouvelle famille d'alcaloides bicycliques et oligocycliques, nommee myrmicarine, a ete isolee de glandes a poisons de fourmis d'afrique de type mirmicinae. La plupart de ces composes possedent en totalite ou en partie un motif hexahydropyrroloindolizine contenant un centre stereogene dont la configuration absolue n'est pas connue. Nous avons entrepris la synthese de ces alcaloides sous forme enantiopure. Dans un premier temps, suivant une strategie divergente basee sur des reactions de substitution electrophile regioselective sur un noyau pyrrolique nous avons synthetise un motif hexahydropyrroloindolizinone sous forme enantiopure, et par la suite les myrmicarines 217 et 215 (a et b). Dans un deuxieme temps, nous avons etudie la regioselectivite des reactions d'acylation de type vilsmeier-haack sur le tricycle quasi-symetrique hexahydropyrroloindolizine. Des conditions ideales ont ete mises au point permettant une substitution electrophile regiospecifique. Cette etude a ouvert une deuxieme voie d'acces aux myrmicarines 217 et 215 (a et b). Enfin nous avons propose deux voies d'acces a la myrmicarine 430 dont une est basee sur l'auto condensation des myrmicarines 215 (a et b) et pourrait etre assimilee a une synthese biomimetique de cet alcaloide.

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Lemétais, Aurélie. "Catalyse tandem pour la protection régiosélective de saccharides : vers l’élaboration de sulfoglycolipides mycobactériens". Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112273.

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L’accès par voie chimique à des oligosaccharides nécessite souvent le recours à de nombreuses étapes de protection-déprotection. Au cours de ce projet de thèse, une méthodologie pour la protection régiosélective et orthogonale des fonctions alcool de disaccharides dérivant de la biomasse a tout d’abord été développée. Les glycopyranosides protégés ont été préparés par catalyse tandem au FeCl3∙6H2O en réalisant dans le même pot des réactions d’acétalation, d’éthérification réductrice, d’acétylation et/ou d’ouverture réductrice régiosélective d’acétals. Dans un second temps, une stratégie de synthèse flexible, rapide et performante pour accéder à des sulfoglycolipides diacylés et tétraacylés comportant un cœur tréhalose a été mise au point. Ces molécules sont produites par Mycobacterium tuberculosis, l’agent pathogène responsable de la tuberculose, et les sulfoglycolipides diacylés pourraient permettre l’élaboration d’un nouveau vaccin contre cette maladie. Des sulfoglycolipides diacylés et tétraacylés comportant des chaînes monométhylées chirales ont été obtenus. Les précurseurs des acides gras chiraux utilisés au cours de la synthèse ont été analysés par spectroscopie RMN du deutérium en abondance naturelle dans des cristaux liquides chiraux
The synthesis of oligosaccharides often requires long sequences of protection-deprotection steps. For a rapid access to suitably protected glycopyranosides, we have developed a one-pot regioselective protection strategy based on FeCl3∙6H2O-tandem catalyzed reactions (acetalation, acetylation, reductive etherification, regioselective ring opening of acetal). This procedure was applied to persilylated disaccharides derived from biomass. This methodology allowed the development of a fast, efficient and flexible access to diacylated and tetraacylated sulfoglycolipids based on a trehalose core. These molecules are found in the cell wall of Mycobacterium tuberculosis and the diacylated sulfoglycolipids appear to be promising candidates for the development of a new tuberculosis vaccine. Synthetics diacylated and tetraacylated sulfoglycolipids bearing chiral monomethylated fatty chains were produced. The chiral fatty-acid precursors, used in the procedure, were synthetized and analyzed by NMR spectroscopy of natural abundance deuterium in chiral liquid crystals

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Capítulos de livros sobre o assunto "Regioselective reduction"

1

Brown, R. C. D. "Regioselective Reduction of Diepoxy Alcohols". In Alcohols, 1. Georg Thieme Verlag KG, 2008. http://dx.doi.org/10.1055/sos-sd-036-00665.

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Clayden, Jonathan. "Regioselective Synthesis of Organolithiums by C–X Reduction". In Organolithiums: Selectivity for Synthesis, 149–68. Elsevier, 2002. http://dx.doi.org/10.1016/s1460-1567(02)80035-6.

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Li, W.-R. "Regioselective Reduction with the Sodium Borohydride/Iodine System". In Three Carbon-Heteroatom Bonds: Esters and Lactones; Peroxy Acids and R(CO)OX Compounds; R(CO)X, X=S, Se, Te, 1. Georg Thieme Verlag KG, 2005. http://dx.doi.org/10.1055/sos-sd-021-00202.

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4

Pereira, M. Manuela A. "13.3. Regioselective 1,2-Reduction of an α,β-Unsaturated Ketone. A Green Experiment". In Comprehensive Organic Chemistry Experiments for the Laboratory Classroom, 784–88. The Royal Society of Chemistry, 2016. http://dx.doi.org/10.1039/9781849739634-00784.

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Taber, Douglass F. "The Boger Synthesis of (-)-Vindoline". In Organic Synthesis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199965724.003.0096.

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The periwinkle-derived alkaloids vinblastine 2a and vincristine 2b are still mainstays of cancer chemotherapy. The more complex half of these dimeric alkaloids, vindoline 1, presents a formidable challenge for total synthesis. Building on his previous work (Organic Lett. 2005, 7, 4539), Dale L. Boger of Scripps/La Jolla devised (J. Am. Chem. Soc. 2010, 132, 3685) a strikingly simple solution to this problem based on sequential cycloaddition. The starting point for the synthesis was the ester 3, derived from D-asparagine. This was extended to 4, condensation of which with 5 gave the enol ether 6. On heating, 7 cyclized to 8, which lost N2 to give the zwitterion 9. Addition of the intermediate 9 to the indole then gave 10. In one reaction, the entire ring system of vindoline, appropriately oxygenated, was assembled, with the original stereogenic center from D-asparagine directing the relative and absolute configuration of the final product. To complete the synthesis, the pendant carbon on 11 had to be incorporated into the pentacyclic skeleton. After adjusting the relative configuration of the secondary alcohol, the N was rendered nucleophilic by reduction of the amide to the amine. Oxidation delivered 14, which on activation as the tosylate smoothly rearranged to the ketone 15. Reduction and regioselective dehydration then completed the synthesis of vindoline 1.

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Brégier, Frédérique, Jérémy Godard, Jordan Thiais, Soukaina Bouramtane, Alexia Moulin, Yves Champavier, Alexis Mailleau, Vincent Chaleix e Vincent Sol. "Regioselective reduction of 5-aryl-10,15,20-tris(pyridyl) porphyrin to 5-aryl-10,15,20-tris(pyridyl)dihydroporphyrin (chlorin)". In Porphyrin Science by Women, 568–85. WORLD SCIENTIFIC, 2021. http://dx.doi.org/10.1142/9789811223556_0045.

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7

S. Alharbi, Abdulrahman, Abeer N. Al-Romaizan e Reda M. Abdel-Rahman. "A Review on Synthesis, Chemistry, and Medicinal Properties of Benzothiazines and their Related Scaffolds". In Advances in Organic Synthesis, 291–336. BENTHAM SCIENCE PUBLISHERS, 2022. http://dx.doi.org/10.2174/9789815040524122170008.

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Background: Sulfur and nitrogen heterocyclic systems, especially benzothiazine derivatives, play a vital role in the search for newer drugs due to a significant scientific interest owing to their broad range of synthetic values, various routes, and pharmacological properties. It is known that benzothiazines are divided into five units: 1,2-, 2,1-, 1,3-, 3,1-, and 1,4-benzothiazines. Incorporating two moieties (benzo and thiazine) increases the biological activity of both, and thus their values synthesize new heteropolycyclic systems. Considering their diverse roles in the biological area and synthesis chemistry, huge effects have been found in developing novel and efficient methodologies to synthesize various benzothiazine moieties with different substitutions. Methods: The present chapter comprises an inclusive vision of new and straightforward synthetic strategies to afford benzothiazine and related systems. This chapter covers various reactions for synthesizing benzothiazines, such as alkylation, acylation, aroylation, halogenation, elimination, rearrangement, ring enlargement, reduction, and oxidation. Besides, it also includes other reactions, like cyclization, addition, condensation, cyclocondensation, metal/acid-catalyzed, hydrolysis, aminolysis, hydrazinolysis, complexation, and enantio/regioselective. Moreover, many benzothiazines have been evaluated for their therapeutic activity. Result: The synthesis and chemical reactions of benzothiazines derivatives have been reported. The preparation approaches of some compounds have been found to involve many steps, and others one-pot, resulting in good to excellent yields. Also, many synthesized compounds have shown medicinal properties, such as aldose reductase,anti-inflammatory, analgesic, antimicrobial, antibacterial, antifungal, anticancer, antiviral, antioxidant, herbicidal, and anticarcinogenic, anti-tubercular, antianthelmintic, and antitumor probes. Conclusion: The chapter covers various methods to synthesize benzothiazines and their derivatives, thereby displaying their biological activities.

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Taber, Douglass F. "The Ma Synthesis of Gracilamine". In Organic Synthesis. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190200794.003.0103.

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The Am aryllidaceae alkaloid gracilamine 3 was isolated in 2005 from the Turkish plant Galanthus gracilis. The supply of the natural product was not sufficient to assess the biological activity. Dawei Ma of the Shanghai Institute of Organic Chemistry envisioned (Angew. Chem. Int. Ed. 2012, 51, 10141) that the pentacyclic skeleton of 3 could be assembled by intramolecular dipolar cycloaddition, converting 1 to 2. The successful completion of the synthesis also enabled the full establishment of the relative configuration of 3. The immediate precursor to the ylide 1 was the aldehyde 9. The preparation of 9 began with the reductive amination of piperonal 4 with tyramine 5. The crude product was formylated to give the amide 6. Oxidative cyclization converted 6 to 7, which was reduced to a 1:1 mixture of diastereomers, only one of which (illustrated) could be carried onto the natural product. The undesired diastereomer was oxidized and recycled. Further reduction gave the amine, which was protected to give 8. With 8 in hand, the stage was set for regioselective von Braun degradation. Exposure to Troc-Cl gave a benzylic chloride that was hydrolyzed with AgNO3 to the benzylic alcohol. Dess-Martin oxidation completed the preparation of the aldehyde 9. Condensation of 9 with leucine ethyl ester 10 gave an imine, which on heating cyclized to racemic 2 with 5:1 diastereocontrol. Other diastereomers were possible, but the constraints of the fused 5/5 system ensured that the alternative transition states were significantly higher in energy. On exposure of the amino alcohol from deprotection of 2 to modified Pfitzner-Moffatt conditions, the amine was again protected and the alcohol was oxidized to the ketone to give 11. On deprotection, the amine added in a conjugate sense to give a ketone that was reduced to gracilamine 3 The diene 9 is prochiral, so there is the possibility that chiral catalysis could set the absolute configuration of 2 and so of 3. Attempts by the authors to catalyze the intramolecular dipolar cycloaddition were, however, so far not successful.

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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 Qin Synthesis of (+)-Gelsemine". In Organic Synthesis. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190200794.003.0093.

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(+)-Gelsemine 3 has no particular biological activity, but its intricate architecture continues to inspire the ingenuity of organic synthesis chemists. Yong Qin of Sichuan University devised (Angew. Chem. Int. Ed. 2012, 51, 4909) an enantiospecific synthesis of 3, a key step of which was the cyclization of 1 to 2. The starting material for the synthesis was the inexpensive diethyl tartrate 4, which was converted over six steps into the N-sulfonyl aziridine 5. The addition of 6 was highly regioselective, leading, after N-methylation, to the alkyne 7. After alcohol protection, the sulfonyl group was smoothly removed by sonication with Mg powder in methanol. Addition to acryonitrile then gave 8. Semihydrogenation of 8 set the stage for construction of the lactone 1. The anion of 1, generated by exposure to LDA, cyclized to 2 with significant diastereoselectivity. The lactone of 2 was selectively reduced with Dibal, to give an aldehyde that was protected as the acetal. The exposed primary alcohol was then oxidized to the aldehyde 9. Condensation of 9 with the enolate of 10 followed by dehydration delivered the alkene 11, with the stage set for a second intramolecular nitrile anion addition. In the event, the cyclization of 11 delivered 12, the wrong diastereomer. This was corrected by selenation and oxidation to give an alkene, which was hydrogenated to 13. Exposure to acid deprotected both the MOM group of 13 and the acetal, then promoted cyclization to 14. Reduction of the nitrile to the aldehyde followed by methylenation completed the synthesis of (+)-gelsemine 3. It should be noted that the hydrogenation to form 13 had to be carried out carefully to avoid premature removal of the N-methoxy group. That group was critical for the successful conversion of 13 to 14.

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Trabalhos de conferências sobre o assunto "Regioselective reduction"

1

Custódio, Cíntia de Andrade, e Simon J. Garden. "Regioselective reduction of 1-amino-2,4-dinitrobenzenes". In 15th Brazilian Meeting on Organic Synthesis. São Paulo: Editora Edgard Blücher, 2013. http://dx.doi.org/10.5151/chempro-15bmos-bmos2013_2013819201721.

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2

Maksutova, A. I., e M. D. Tsymliakov. "REGIOSELECTIVE 2,4-DINITROARENE REDUCTION AS A PATH TO VARIOUS HETEROCYCLIC COMPOUNDS AND POTENT QUINONE REDUCTASE 2 (NQO2) INHIBITORS". In MedChem-Russia 2021. 5-я Российская конференция по медицинской химии с международным участием «МедХим-Россия 2021». Издательство Волгоградского государственного медицинского университета, 2021. http://dx.doi.org/10.19163/medchemrussia2021-2021-404.

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Pino-González, M., Noé Bernal e Antonio Romero. "Reductions of Monosaccharide Derivative Epoxyamides to Epoxyalcohols and Regioselective Epoxide Opening". In The 12th International Electronic Conference on Synthetic Organic Chemistry. Basel, Switzerland: MDPI, 2008. http://dx.doi.org/10.3390/ecsoc-12-01226.

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Wang, Cai-Xia, Xin-Hua Li, Cai-Xia Zhao e Hong-Ping Xiao. "Reductive, Regioselective Addition of Benzenethiyl Radical to Alkynes via 2,2'-Dithiosalicylic Acid". In 2015 International Conference on Medicine and Biopharmaceutical. WORLD SCIENTIFIC, 2016. http://dx.doi.org/10.1142/9789814719810_0058.

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