GB929656A - Production of esters of alkylboronic acids and dialkylborinic acids - Google Patents

Abstract

Esters of boronic and borinic acids having the formula RnB(OR1)3-n, wherein R represents an alkyl radical having at least two carbon atoms which may be substituted by aryl groups or halogen atoms, n is 1 or 2, and R1 represents alkyl, cycloalkyl, alkoxyalkyl, aminoalkyl, alkylaminoalkyl, aryl, alkoxyaryl, aminoaryl or alkylaminoaryl or 2R1 represents alkylene when n is 1, are made by reacting an ester of a halogeno-boric acid having the formula XnB(OR1)3-n wherein X means a halogen, n and R1 are as above, with an olefin and an alkali metal or alkaline earth metal borohydride and recovering the ester formed. The olefines are those derived from radical R by splitting off a hydrogen atom and include olefines of the ethylene series, halo-olefines and arylolefines. Monofluoroboronic acid esters and difluoroborinic acid esters are suitable starting materials. Temperatures between -20 DEG C. and the decomposition point of the reactants or the boiling point of any solvent may be used, the optimum temperature lying between 30 and 100 DEG C. The haloboric acid esters may be made in situ by introducing boron trihalide into a mixture of borohydride and boric acid ester in a solvent. Thus the boronic or borinic acid esters may be made by reacting akali metal or alkaline earth metal borohydrides with boric acid esters B(OR1)3, alkyl ether addition compounds of boron trihalide and olefines. Esters of alkylboronic acid or dialkylborinic acids with alkanols, such as methanol, ethanol, propanol, butanol or amyl alcohol, can be converted into esters of higher boiling alcohols, alkoxyalkyl alcohols or aminoalcohols by heating the esters of said alkanols with said higher-boiling alcohols, if necessary in a vacuum, to temperatures between the boiling point of the lower alcohol and that of the higher boiling alcohol, until the alkanol bound in the ester is completely distilled off and recovering the desired ester.