Rhodium-Catalyzed Addition of Organoboronic Acids to Aldehydes.

Highly inert to ionic additions to aldehydes, aryl- and 1-alkenylboronic acids succumb to a catalytic variant mediated by a [Rh(acac)(CO)2 ]-diphosphane complex in aqueous phase at 80-95°C to yield secondary alcohols [Eq. (a)]. A key step in the catalytic cycle is the transmetalation between the boron reagent and the rhodium complex. Ln =diphosphane (e.g. 1,1'-bis(diphenylphosphanyl)ferrocene); R=aryl, 1-alkenyl; R'=alkyl, aryl; acac=acetylacetonate. © 1998 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.