Addition Reactions of Bis(pinacolato)diborane(4) to Carbonyl Enones and Synthesis of (pinacolato)2BCH2B and (pinacolato)2BCH2CH2B by Insertion and Coupling

The title compound adds to α,β-unsaturated carbonyls to give the products of 1,4-addition after hydrolysis of the intermediate boron enolates, in 68−86% isolated yield (four examples). In addition, we discovered that diazomethane reacts with bis(pinacolato)diborane to insert methylene to give (pinacolato)2BCH2B in 83% yield. An alternative synthesis involved coupling of (pinacolato)BCH2I with various metals.