Reductions in Organic Synthesis

A survey of hydride reductions in organic chemistry from its beginnings has been made. Persuaded by Alfred Stock's book entitled "The Hydrides of Boron and Silicon" that he received as a graduation gift in 1936 from his classmate (now his wife) Sarah Baylen, the senior author undertook research with Professor H. I. Schlesinger and Dr. A. B. Burg, exploring the chemistry of diborane. His Ph.D. research, begun in 1936 involved a study of the reaction of diborane with aldehydes and ketones, and other compounds with a carbonyl group. This development initiated the hydride era of organic reductions. Necessities of WWII research led to the discovery of sodium borohydride and the discovery of the alkali metal hydride route to diborane. The systematic study to modify sodium borohydride and lithium aluminum hydride led to a broad spectrum of reagents for selective reductions. It is now possible to selectively reduce one functional group in the presence of another. The study of the reduction characteristics of sodium borohydride led to the discovery of hydroboration and the versatile chemistry of organoboranes. An examination of the hydroboration of α-pinene led to the discovery of an efficient asymmetric hydroboration agent, diisopinocampheylborane, Ipc2BH. This led to the devlopment of a general asymmetric synthesis and to the discovery of efficient reagents for asymmetric reduction. Research progressed, one discovery leading to another, opening up a whole new continent of chemistry.