ORGANOBORANES .54. EXPLORATION OF THE REACTIONS OF (ALPHA-HALOALLYL)LITHIUM WITH ORGANOBORANE DERIVATIVES - SIMPLE AND CONVENIENT PROCEDURE FOR THE SYNTHESIS OF 3-CARBON HOMOLOGATED BORONATE ESTERS AND TERMINAL ALKENES

The synthetic utility of (alpha-haloallyl)lithium generated in situ for the facile transfer reaction of various organoborane derivatives, such as R3B, R2BOR', and RB(OR')2, has been explored. This has led to the synthesis of alpha-vinylboronate esters, RCH(CH=CH2)B(OR')2, which are readily isomerized thermally to the corresponding allylboronate esters with the boron atom on the less substituted carbon atom, RCH=CHCH2B(OR')2. Catalytic hydrogenation of these allylboronate esters furnishes saturated boronate esters, RCH2CH2CH2B(OR')2, providing a three-carbon homologation of the original R-B < moiety. Protonolysis in place of hydrogenation affords the corresponding terminal alkenes RCH2CH=CH2.