Osmium-catalyzed asymmetric dihydroxylation of olefins by H2O2 using a biomimetic flavin-based coupled catalytic system

Selective cis-dihydroxylation of olefins with the aid of a triple catalytic system using H2O2 as the terminal oxidant has been developed. In this proc ess Os(VI) is recycled to Os(VIII) by a coupled electron-transfer-mediator system based on N-methylmorpholine and a biomimetic flavin, leading to a mi ld and selective electron transfer. Aliphatic, aromatic, and functionalized olefins were successfully cis-dihydroxylated, employing the triple catalyt ic system. The present biomimetic catalytic system works well in asymmetric dihydroxylation and gave optically active diols in good isolated yields an d high enantiomeric excesses (up to 99% ee).