Kinetic and mechanistic study of the H-transfer reduction of dimethyl itaconate by a Rh/TPPTS catalyst under biphasic conditions: Evidence for a rhodametallacycle intermediate

The H-transfer reduction of dimethyl itaconate under biphasic catalysis usi ng sodium formate/water as the hydrogen source with a Rh/TPPTS complex was studied. Labelling experiments reveal that the reduction proceeds through a 1,3-hydrogen addition. Kinetic studies allow us to propose a catalytic cyc le going through a rhodametallacyclobutane intermediate with a rate-determi ning step involving sodium formate. A formal kinetic rate law was then deri ved from this mechanism which accounts for the results. This work evidences the switch between the mechanism of diacid reduction and that of the corre sponding eaters.