Photocatalytic Oxygenation of Cyclohexene Initiated by Excitation of [UO 2 (OPCyPh 2 ) 4 ] 2+ under Visible Light

Abstract

Oxygenation reaction of cyclohexene was studied under the presence of a fourfold UO 22+ complex with cyclohexyldiphenylphosphine oxide, [UO 2 (OPCyPh 2 ) 4 ] 2+ , and blue light irradiation at 436 nm in acetonitrile. As a result, 1,6-hexanedial, cyclohexene oxide, 2-cyclohexen-1-one, and 2-cyclohexen-1-ol were photocatalytically generated as oxygenated products with turnover frequency = 6.7 h -1 . In contrast, dimerization of cyclohexene was observed under Ar atmosphere. This implies that a hydrogen atom at the allyl position is abstracted by photoexcited [UO 2 (OPCyPh 2 ) 4 ] 2+ to give a cyclohexene radical and a U(V) intermediate [U V O 2 (OPCyPh 2 ) 4 ] + , being well supported by the density functional theory calculation. Under an O 2 atmosphere, the former reacts with dissolved O 2 to give 2-cyclohexen-1-one and 2-cyclohexen-1-ol. Dissolved O 2 would be activated by the U(V) intermediate to afford O 22- in the end, which drives oxygenation of the C=C bond of unreacted cyclohexene.