Design, synthesis and application of bipyridine-N,N′-dioxide catalysts in asymmetric synthesis of chiral cyclopropanes

Abstract

A novel type of highly efficient chiral C₂-symmetric bipyridine-N,N′-dioxide ligands was prepared from L-octahydroindole-2-carboxylic acid and successfully applied in the synthesis of optically pure 1,2,3-trisubstituted cyclopropanes employing sulfoxonium ylides with α,β-unsaturated 2-acyl imidazoles, affording the corresponding adducts in 88–98% yields with up to 99% enantioselectivity and >20 : 1 dr under mild conditions with broad scope. In addition, a scale-up experiment and synthetic transformations of the cycloadducts further highlighted the synthetic utility.