Transition-metal-catalyzed addition of organometallic reagents to aldehydes is a key method for the synthesis of substituted secondary alcohols.[1] Various organometallic reagents, such as organomagnesium,[2]-zinc,[1, 12e–i]-lithium,[3]-silane,[4]-stannane [5] and-boron,[6] have been used in these addition reactions. Among them, organoboron reagents have gained much attention due to the advantages of air and moisture stability, low toxicity, and ...