Cationic ruthenium hydride catalysed and chelate assisted C-O bond cleavage of 2-acetyl-aryl ethers: A model compound for lignin de-polymerization

Abstract

2-Acetyl containing a neighbouring aromatic ether group regioselectively reacts with the cyclopentene in the presence of cationic Ru-H catalyst [(C6H6)(PCy3)(CO)RuH]+BF4− in aromatic hydrocarbon solvents. The alkyl moiety of ether can be any of cyclic, methyl, butyl, benzyl, phenyl and allyl groups. Chelation plays a key role in regioselectivity directing the C-O bond cleavage reaction. The reactions of 2-acetyl derivatives of aryl-ethers under these conditions affect the corresponding products having onlyphenol -OH group at the aromatic ring. Cleavage of the sp3 C-O bond occurs selectively rather than sp2 C-O bond. The method has successfully extended to C-O bond cleavage of flavanone biomolecule and strongly possible to extend regioselectively depolymerize lignin biomolecules.