Standard Article

Reductive Aminations of Carbonyl Compounds with Borohydride and Borane Reducing Agents

  1. Ellen W. Baxter,
  2. Allen B. Reitz

Published Online: 15 APR 2004

DOI: 10.1002/0471264180.or059.01

Organic Reactions

Organic Reactions

How to Cite

Baxter, E. W. and Reitz, A. B. 2004. Reductive Aminations of Carbonyl Compounds with Borohydride and Borane Reducing Agents. Organic Reactions. 59:1:1–714.

Author Information

  1. The R. W. Johnson Pharmaceutical Research Institute, Drug Discovery Division, Spring House, Pennsylvania

Publication History

  1. Published Online: 15 APR 2004

Abstract

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.

Keywords:

  • organic reaction(s);
  • organic synthesis;
  • reaction(s);
  • synthesis;
  • reductive amination;
  • condensation;
  • alkylation;
  • reductive alkylation;
  • reduction;
  • amination;
  • carbonyl;
  • amine;
  • reducing agent(s);
  • borohydride;
  • borane;
  • carbon-nitrogen bond(s);
  • C[BOND]N bond(s)