Catalytic Cycloetherification Using Bifunctional Thiourea Catalysts

Significance

The Matsubara group presents a catalytic asymmetric cycloetherification for the synthesis of enantioenriched 2-substituted tetra­hydrofuran (THF) derivatives via an intramolecular oxy-Michael addition using bifunctional thiourea catalyst 1. 2-Substituted THFs were obtained in high enantioselectivities and excellent isolated yields in the presence of 3 mol% of quinine-derived bifunctional catalyst 1. The authors show that the catalyst loading could be lowered to 1 mol% without loss of optical purity. Also, product 2 was transformed to a valuable synthetic intermediate 3 by means of Baeyer-Villiger oxidation and reduction.