Transition-metal-free reductive cleavage of lignin-related C-O bonds by an activated silane

Abstract

Reported herein is a transition-metal-free protocol for the efficient reductive cleavage of diaryl and aryl alkyl ethers. The combination of triethylsilane with simple bases forms an unusually powerful reductive couple that affords regioselective rupture of lignin- and coal-related C-O bonds in arom. ethers. Interestingly, this is accompanied by ortho-directed C-H silylation that becomes preferred with certain bases and temp. re-gimes. However, the tuning of selectivity proved possible thus enabling the development of a practical method for the title transformation, as illustrated by the redn. of lignin model compds. to their corresponding phenolic and arom. constituents.