Development of Novel Guanidine-Bisurea Bifunctional Organocatalysts and their Application to Asymmetric α-Hydroxylation of Tetralone-derived β-Keto Esters

A series of guanidine-bisurea bifunctional organocatalysts 4, with chiral centres located outside the urea groups, were synthesized. The novel catalyst 4 is conformationally more flexible than the original catalyst 1. In alpha-hydroxylation of tetralone-derived beta-keto esters, 4 afforded the corresponding alcohols in high yields with moderate enantioselectivity.