Radical Differentiation of Two Ester Groups in Unsymmetrical Diazomalonates for Highly Asymmetric Olefin Cyclopropanation
X. Peter Zhang reports on a highly asymmetric olefin cyclopropanation using a radical differentiation method.
Metal-catalyzed asymmetric cyclopropanation of alkenes with diazomalonates offers a potentially attractive approach for the construction of 1,1-cyclopropane diesters – a class of valuable three-membered carbocycles that serve as important building blocks for organic synthesis – with effective control of stereoselectivity. Due to the inherent stereocontrol challenge associated with two similar electron-withdrawing ester groups, the existing catalytic systems involving electrophilic metallocarbene intermediates have shown limited substrate scope and have been hampered by low enantioselectivity. One conceptually different strategy for asymmetric cyclopropanation with unsymmetrical diazomalonates has recently been reported by the research group of Professor X. Peter Zhang at Boston College (Chestnut Hill, MA, USA).