A Sterically Bulky Cyclic Thiourea as an Efficient Ligand for Palladium-Catalyzed Aerobic Oxidation of Alcohols

Abstract

Sterically bulky N,N¢-disubstituted cyclic thiourea ligand L1 has been demonstrated as an efficient ligand in palladium-catalyzed oxidation of alcohols using molecular oxygen as an oxidant. This new catalyst system has been applied to a wide variety of substrates such as benzylic alcohols, aliphatic secondary alcohols and allylic alcohols, producing the corresponding carbonyl compounds in good to excellent yields.

Key words

ligands - palladium - homogenous catalysis - alcohols - oxidation

References and Notes

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13

L1 is a highly efficient ligand for Heck reactions; see ref. 11a. L2-4 were prepared following the similar procedures.

14

Other reaction parameters, including palladium sources, solvents, and bases, were examined and the reported conditions were found optimal. The effect of 3 Å molecular sieves was found to give deleterious effect on yields because of serious Pd-black formation.