Chiral base promoted enantioselective rearrangement of organophosphorus epoxides

Cinchona alkaloids serve as effective chiral bases for enantioselective rearrangement of 3,4-epoxyphospholane oxides resulting in the formation of P,C-chirogenic 4-hydroxy-2-phospholene derivatives with up to 52% ee. A stereochemical course of the epoxide rearrangement involving anti β-proton abstraction is proposed. 3,4-Epoxy-1-phospholane-borane rearranges to 4-hydroxy-2-phospholene-borane of 55% ee on treatment with sec-BuLi/sparteine base system.