Computational study on the vanadium-catalyzed asymmetric oxidation of sulfides

COMP 219

David Balcells, dbalcells@iciq.es1, Feliu Maseras, fmaseras@iciq.es1, and Gregori Ujaque, gregori@klingon.uab.es2. (1) Feliu Maseras Research Group, Institute of Chemical Research of Catalonia (ICIQ), Av. Pa´sos Catalans, s/n, 43007 Tarragona, Spain, (2) Department of Chemistry, Universitat Autonoma de Barcelona, Unitat de Quimica Fisica, Edifici Cn, 08193 Bellaterra, Spain
Chiral complexes of vanadium catalyze the oxidation of 1,2-bis(tert-butyl)disulfide. We carried out a DFT study of this reaction on a model system that gave rise to the following conclusions: 1) the catalyst is a hydroperoxo V(+5) complex and 2) the oxidation consists of a direct oxygen transfer step. Then we studied the full catalytic system using a QM/MM method. We found two different diastereoisomers of the catalyst: a (pro-R) and b (pro-S); see figure. Our results show that the enantioselectivity depends on the energy difference between a and b (Eab) and the energy difference between the pro-R and pro-S transition states for a given form of the catalyst (Ea). Eab is modulated by R3 and Ea by R1.