Synthesis of a new chiral nonracemic C2-symmetric 2,2′-bipyridyl ligand and its application in copper(I)-catalyzed enantioselective cyclopropanation reactions

An efficient synthesis of a low molecular weight, chiral nonracemic and C-2-symmetric bipyridyl ligand is reported. The ligand was prepared using a catalytic asymmetric dihydroxylation reaction of a pyrindine as a key step. The ligand was evaluated in the asymmetric copper(l)catalyzed cyclopropanation reactions of a series of alkenes and diazoesters. Very high diastereoselectivities and enantioselectivities were observed (>95:5 dr and up to 99% ee). These are the highest reported stereoselectivities for a chiral bipyridyl ligand.