Sodium Borohydride in Carboxylic Acid Media. A Review of the Synthetic Utility of Acyloxyborohydrides

Gribble, Gordon W.; Nutaitis, Charles F.

doi:10.1080/00304948509355522

Cited by 168 publications

(43 citation statements)

References 108 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Two alternative procedures were developed for preparation of 1-alkyl-substituted 1,2,4-triazepane-3-thiones/ones. The first involves reductive alkylation of 2,4,5,6-tetrahydro-3H-1,2,4triazepine-3-thiones/ones 3 with sodium borohydride in carboxylic acid media [69][70][71][72]. We found that monocyclic triazepines 3a,b smoothly reacted with NaBH4 (6 equiv.)…”

Section: Resultsmentioning

confidence: 94%

“…This reaction was completed with 10 equivalents of NaBH4 and 108.3 equivalents of AcOH to produce the target 7n in 94% yield with excellent trans-diastereoselectivity (trans:cis = 98:2, Table 2, entry 16). Higher stereoselectivity in the reduction of 3k with NaBH(OAc)3, in situ generated from NaBH4 and AcOH [69], compared with NaBH3CN (trans:cis = 82:18, Table 1, entry 11) can be explained in terms of steric approach control (see Figure 2) considering a greater steric bulk of reducing reagent in the first case.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

A General Stereoselective Approach to 1,2,4-Triazepane-3-thiones/ones via Reduction or Reductive Alkylation of 2,4,5,6-Tetrahydro-3H-1,2,4-triazepine-3-thiones/ones

Fesenko

Шуталев

2018

22nd International Electronic Conference on Synthetic Organic Chemistry

View full text Add to dashboard Cite

A general stereoselective approach to previously unknown 1,2,4-triazepane-3-thiones/ones based on reduction or reductive alkylation of readily available 2,4,5,6-tetrahydro-3H-1,2,4-triazepine- 3-thiones/ones has been developed. The approach involved treatment of tetrahydrotriazepines with sodium cyanoborohydride in MeOH at pH 3 or with sodium borohydride and excess of carboxylic acid in tetrahydrofuran to give 1-unsubstituted or 1-alkyl-substituted 1,2,4-triazepane-3- thiones/ones, respectively. The latter were also prepared by reaction of 1-unsubstituted 1,2,4- triazepane-3-thiones/ones with sodium cyanoborohydride and aldehyde in MeOH in the presence of AcOH.

show abstract

Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

A General Stereoselective Approach to 1,2,4-Triazepane-3-thiones/ones via Reduction or Reductive Alkylation of 2,4,5,6-Tetrahydro-3H-1,2,4-triazepine-3-thiones/ones

Fesenko

Шуталев

2018

22nd International Electronic Conference on Synthetic Organic Chemistry

View full text Add to dashboard Cite

show abstract

“…indoles [9] and other heterocycles [10]; and (ii) the wide use of borohydride reducing agents for the reduction of imines generated either in situ or via a two-step process from a variety of aromatic aldehydes and amines [11], the use of a reductive alkylation strategy for the modification of 1 using a series of hydroxybenzaldehydes appeared as an attractive starting point for our study.…”

Section: Discussionmentioning

confidence: 99%

Reductive alkylation of aminofluorans: A simple route to intrinsically thermochromic fluorans

2013

View full text Add to dashboard Cite

“…(6) Nas reduções de ácidos carboxílicos por borano tem sido proposta também a formação de triacetoxiboro-hidretos como intermediários (Equação 7) 52 . Entretanto, os efeitos estéricos e indutivos dos três grupos acetoxila tornam este tipo de intermediário desfavorecido termodinamicamente e sugerem um envolvimento pouco significativo de triacetoxiboro-hidretos no mecanismo de redução de ácidos carboxílicos por boranos.…”

Section: Reatividade Das Amidas Em Reduções Por Boranosunclassified

Redução de amidas por boranos

2002

View full text Add to dashboard Cite

Recebido em 27/3/01; aceito em 25/7/01 REDUCTION OF AMIDES BY BORANES. Despite the fact that boranes are frequently used in amide reductions, the reaction mechanisms of the involved are note well known. This work presents the results of a bibliographic search on probable amide reduction mechanisms and an analysis of the existing literature. Steric and electronic effects were considered in light of reactivity since it could be concluded that the formation of intermediates and products depends mainly on the substitution patterns of both the boron and nitrogen atoms. Otherwise, results described in the literature for the reactions of boranes, sodium borohydride, lithium aluminum hydride, alkylboranes or haloboranes with others functional groups such as carboxylic acids, esters, ketones and alkenes were analysed with the aim to obtain something about the N-substituted amide reactions employing boranes.Keywords: amides; reactivity of boranes; reduction. INTRODUÇÃOAmidas estão envolvidas em vários processos químicos e bioló-gicos e têm sido empregadas em diversas classes de medicamentos como hipnóticos (zolpidem, zopiclone e acecarbromal), anticonvulsantes (carbamazepina, felbamato e progabida), tranqüilizan-tes (metilprilona e glutetimida), relaxantes musculares (alildietilacetamida, valnoctamida e oxanamida) e antivirais (AZT e ribavirin) 1-3 . Além disto, as amidas são empregadas também na síntese de agentes radiofarmacêuticos em medicina nuclear 4 .De um modo geral, as propriedades químicas e biológicas das amidas estão relacionadas com a ordem da ligação carbono-nitrogê-nio, a qual expressa a deslocalização eletrônica entre os heteroátomos, sendo influenciada por fatores estéricos e eletrônicos dos grupos substituintes presentes tanto no nitrogênio quanto no carbono carbonílico. Devido à deslocalização eletrônica, essa ligação (denominada também de ligação peptídica) apresenta um alto grau de rigidez, com barreiras de energia rotacional variando entre 50 e 100 kJ/mol 5,6 . A rigidez da ligação carbono-nitrogênio proporciona uma planaridade ao grupo amido em peptídeos e proteínas, a qual, somada aos efeitos de ligações de hidrogênio intramoleculares, determina formas estruturais helicoidais (Figura 1).Nos processos químicos, as reduções de amidas têm sido muito empregadas no desenvolvimento de metodologias para formação de aminas, substâncias também importantes quimicamente 8 . Os procedimentos utilizados para reduções de amidas podem ser agrupados em quatro tipos: reações eletroquímicas; reações com metais; reduções nucleofílicas e reduções eletrofílicas.As reações eletroquímicas e aquelas envolvendo metais são dependentes das condições de reação 9,10 , podendo levar à formação competitiva entre aminas, aldeídos ou álcoois [11][12][13][14][15][16][17] . As reduções nucleofílicas, empregando principalmente boro-hidreto de sódio (NaBH 4 ), hidreto de lítio e alumínio (LiAlH 4 ) e seus derivados 18-28 , proporcionam, além de aminas, a formação de outros produtos de reação. Assim, tris-(dialquilamino)-alumino-hidreto...

show abstract

Sodium Borohydride in Carboxylic Acid Media. A Review of the Synthetic Utility of Acyloxyborohydrides

Cited by 168 publications

References 108 publications

A General Stereoselective Approach to 1,2,4-Triazepane-3-thiones/ones via Reduction or Reductive Alkylation of 2,4,5,6-Tetrahydro-3H-1,2,4-triazepine-3-thiones/ones

A General Stereoselective Approach to 1,2,4-Triazepane-3-thiones/ones via Reduction or Reductive Alkylation of 2,4,5,6-Tetrahydro-3H-1,2,4-triazepine-3-thiones/ones

Reductive alkylation of aminofluorans: A simple route to intrinsically thermochromic fluorans

Redução de amidas por boranos

Contact Info

Product

Resources

About