NEW SYNTHETIC REACTIONS OF ORGANOBORON COMPOUNDS BY TRANSITION-METAL CATALYSTS

The cross-coupling reaction of organoboron compounds with organic halides, the catalytic hydroboration of alkenes and alkynes with catecholborane, and the thioboration reaction of alkynes with 9-organothio-9-borabicyclo[3.3.1]nonanes are described. The palladium-catalyzed cross-coupling reaction of organoboron compounds provides a general and convenient method for the synthesis of stereodefined alkenes, alkadienes or alkenynes, biaryls, and vinylic sulfides. The similar coupling reaction under carbon monoxide (1 atm) produces alkyl vinyl ketones, alkyl aryl ketones, alkyl alkyl ketones and biaryl ketones in exellent yields. The hydroboration of alkenes and alkynes with catecholborane can proceed under very mild conditions with the use of Rh, Pd, or Ni catalysts. It is also observed that catalysts can direct the course of the addition of borane to different regio- or stereoselectivity, compared with uncatalyzed reactions. The reaction is extended to the cis-addition of RS-B compounds to terminal alkynes with the use of Pd(PPh3)4.