Benzo[<i>b</i>]thiophene derivatives. XXV. Condensation and reductive alkylation of 3‐aminoalkylbenzo[<i>b</i>]thiophenes with formaldehyde

Eresko

2011

Chem Heterocycl Comp

Section: Methyl-1-benzothiophen-3-yl)ethylamine (1a)mentioning

confidence: 99%

A convenient method for the synthesis of 1-R-1,2,3,4-tetrahydrobenzothieno-[2,3-c]pyridine derivatives

Eresko

2011

Chem Heterocycl Comp

J. Chem. Soc., Chem. Commun.

“…From the result of the survey (Table l), the 4-p-chlorophenylthio substituent was selected as the most suitable for our purposes. It affords a crystalline substrate ( l f ) 7 which is readily reduced by the organisms chosen for further study, S. cerevisiae and C. guilliermondii, to optically active products (2f) and (3f) respectively. The products are crystalline and readily brought to >%YO e.e.…”

mentioning

confidence: 99%

Biotransformation in organic synthesis: applications of yeast reduction in the synthesis of 3,5-dihydroxy esters of high optical purity

Christen¹,

Crout²

1988

All four stereoisomers of methyl 6-(p-chlorophenylthio)-3,5-dihydroxyhexanoate have been synthesised by a route in which the key introduction of chirality was effected by an appropriate yeast reduction.Because polyoxygenated units occur in many polyether and biological conversion of a (3-keto ester into a (3-hydroxy ester macrolide antibiotics' their synthesis has attracted much followed by chain extension to generate a 3-oxo-5-hydroxy attention. We have investigated an approach which would ester. Reduction of the chain-extended system could then be provide an iterative route to such systems. As outlined in effected either by chemical procedures or by a further Scheme 1, this was envisaged as beginning with stereospecific biotransformation. We have found that such a sequence,

Reductive Aminations of Carbonyl Compounds with Borohydride and Borane Reducing Agents

2002

Reductive amination is an important tool for synthetic organic chemists in the construction of carbon‐nitrogen bonds. This reaction, also termed reductive alkylation, involves condensation of an aldehyde or ketone with an amine in the presence of a reducing agent. A wide variety of substrates can be used including aliphatic and aromatic aldehydes and ketones, and even benzophenones. A range of amines from ammonia to aromatic amines, including those with electron‐withdrawing substituents, can be employed. For particularly sluggish reactions, such as those involving weakly electrophilic carbonyl groups, poorly nucleophilic amines, or sterically congested reactive centers, additives such as molecular sieves or Lewis acids are often useful. This chapter focuses on those conditions in which the carbonyl component, amine, and reducing reagent react in the same vessel. This review is restricted to reductive aminations using borohydride and borane reducing agents. This chapter concentrates on reductive amination chemistry mediated by borohydride and other boron‐containing reducing agents from 1971, the year when sodium cyanoborohydride was introduced, through the middle of 1999. In addition to reductive aminations of aldehyde and ketone substrates, reactions of related structures including acetals, aminals, ketals, carboxylic acids, nitriles, and dicarbonyls that form a nitrogen‐containing ring are reviewed. Intramolecular processes in which the substrate contains both the carbonyl and amine moieties are described. The intramolecular variant is a useful method for preparing cyclic amines. All of the various boron‐containing hydride sources in reductive aminations, including labeled metal hydrides, are reviewed. Instances of reductive aminations that failed are described. Applications of this method to a solid support in parallel synthesis in combinatorial chemistry as well as reductive aminations that proceed in tandem with a second reaction such as reductive lactamizations are discussed.