Ruthenium(II)-catalyzed C-H alkenylations of phenols with removable directing groups

Abstract

Cationic ruthenium(II) complexes enabled oxidative alkenylations of phenols bearing easily cleavable directing groups. The optimized catalytic system allowed twofold CH bond activations with excellent chemo-, site-, and diastereoselectivities. The double CH functionalization process proceeded efficiently in an aerobic fashion under an atmosphere of ambient air. Detailed mechanistic studies were performed and provided strong support for an initial reversible CH bond activation by the formation of six-membered ruthenacycles as the key intermediates.

Keywords: CH activation; alkenylation; catalysis; cross-dehydrogenative coupling; reaction mechanisms; ruthenium.