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. L_n=diphosphane (e.g. 1,1′-bis(diphenylphosphanyl)ferrocene); R=aryl, 1-alkenyl; R′=alkyl, aryl; acac=acetylacetonate.