Generation and Application of Homoenolate Equivalents Utilizing [1,2]-Phospha-Brook Rearrangement under Brønsted Base Catalysis.

A new method for catalytic generation of a homoenolate equivalent and its application to carbon-carbon bond formation was developed by utilizing the [1,2]-phospha-Brook rearrangement under Brønsted base catalysis. The α-oxygenated allyl anions, which can serve as homoenolate equivalents, were catalytically generated in situ by treating readily available chalcones with diethyl phosphite or the pre-formed 1,2-adducts of diethyl phosphite with chalcones in the presence of a catalytic amount of a phosphazene base, P2-tBu. The resulting allyl anions were subsequently trapped by various electrophiles, including Michael acceptors, imines, and aldehydes, providing the corresponding adducts in good yields with moderate to good diastereoselectivities.