Boranes in Organic Chemistry

Publisher Summary This chapter discusses boranes in organic chemistry, diborane as a reducing agent, volatile compounds of uranium, the alkali metal hydride approach to diborane, and alkali metal borohydrides. The search for solvents led to the discovery of sodium borohydride's being an excellent reducing agent for aldehydes and ketones. The search for catalysts to enhance the reducing power of sodium borohydride led to an anomalous result in the reduction of ethyl oleate. Investigation of this anomalous result led to the discovery of hydroboration. Hydroboration made the organoboranes readily available for the first time. This led to a systematic exploration of the chemistry of the organoboranes and established the fact that they constitute the most versatile organometallic available currently. The chapter describes molecular addition compounds and steric strains, steric assistance in solvolysis, the nonclassical ion problem, selective reductions, hydroboration, and versatile organoboranes. On the theoretical side, study of the dissociation of addition compounds of amines with trimethylborane, boron trifluoride, and borane provides a new quantitative approach to steric strains. These studies quickly removed doubts as to the importance of steric effects in chemical behavior and led to the study of related carbon compounds and the establishment of steric effects as an important factor in their behavior. One phase of these studies involved steric assistance to ionization in highly branched tertiary halides and related derivatives.