Asymmetric Copper-Catalyzed Vinylogous Mukaiyama Michael Addition of Cyclic Dienol Silanes to Unsaturated α-Keto Phosphonates

A highly stereoselective vinylogous Mukaiyama Michael reaction (VMMR) leading to α‐keto phosphonate‐containing γ‐butenolides with two stereogenic centers is described. The presented transformation is catalyzed by a combination of a commercially available C2‐symmetric bisoxazoline (BOX) ligand and a copper salt and tolerates a variety of nucleophiles and electrophiles. The stereoselectivities of the reactions are good to excellent and the products are obtained in moderate to high yields. A highly stereoselective vinylogous Mukaiyama Michael reaction (VMMR) of dienol silanes to α‐keto phosphonates leading to γ‐butenolides with two stereogenic centers is described. Good to excellent stereoselectivities have been achieved with a readily available copper(II)/bisoxazoline (BOX) catalyst (see scheme).