Addition compounds of alkali-metal hydrides. 25. Rapid reaction of boronic esters and acids with lithium aluminum hydride. A novel and quantitative synthesis of lithium monoorganylborohydrides

Article abstract of DOI:10.1021/om00083a022

Boronic esters readily react with lithium aluminum hydride in diethyl ether-pentane at 0°C to form the corresponding lithium monoorganylborohydrides and dialkoxyalanes. Under these reaction conditions, the dialkoxyalanes generally precipitate quantitatively from solution. The reaction is essentially quantitative and is broadly applicable to a representative variety of boronic esters. Boronic acids can also be readily converted to the corresponding lithium monoorganylborohydrides by treatment with lithium aluminum hydride. The reaction is quantitative and, like the boronic esters, is broadly applicable to a wide variety of boronic acids. These procedures provide a general, convenient synthesis of lithium monoorganylborohydrides with organic groups of greatly varying steric requirements.