Reduction of Carboxylic acids....

[java]

Convenient Procedure for the Reduction of Carboxylic Acids via Acyloxyborohydrides
Byung Tae Cho and Nung Min Yoon

Bulletin of the Korean Chemical Society Volume 3, Number 4 (1982)

http://journal.kcsnet.or.kr/publi/bul/bu82n4/149.pdf

Abstract:A new convenient method for the reduction of carboxylic acids to the corresponding alcohols via acyloxyborohydrides was explored. Acyloxyborohydrides, prepared from the reaction of various carboxylic acids and sodium borohydride, underwent reduction to the corresponding alcohols readily by the addition of dimethyl sulfate or Lewis acids, such as boron trifluoride etherate and triphenyl borate, presumably through acyloxyboranes. By utilizing this procedure, aliphatic and aromatic acids are rapidly and quantitatively reduced to the corresponding alcohols in terahydrofuran either at room temperature (or at 65¡Æ). This procedure provides selective reduction of carboxylic acids in the presence of halogen, nitro, and heterocyclic rings such as furan and thiophene.

.....................

Conclusion
A new convenient method for the reduction of carboxylic acids to the corresponding alcohols vie acyloxyborohydrides was explored. Acyloxygorohydrides, prepared from the reaction of various carboxylic acisa and sodium borohydride, underwent reduction to the corresponding alcohols readily by the addition of dimethyl sulfate or Lewis acids such as boron trifluoride etherate and triphenylborate, presumably through acyloxyboranes. This procedure should be more convenient for the reduction of carboxylic acids than that with borane, especially in a large scale.the present study provides another major application of sodium borohydride, in borohydride reduction of organic functional groups.