Iron-Catalyzed Highly Enantioselectivecis-Dihydroxylation of Trisubstituted Alkenes with Aqueous H2O2

Reliable methods for enantioselectivecis-dihydroxylation of trisubstituted alkenes are scarce. The iron(II) complexcis-alpha-[Fe-II(2-Me-2-BQPN)(OTf)(2)], which bears a tetradentate N(4)ligand (Me-2-BQPN=(R,R)-N,N '-dimethyl-N,N '-bis(2-methylquinolin-8-yl)-1,2-diphenylethane-1,2-diamine), was prepared and characterized. With this complex as the catalyst, a broad range of trisubstituted electron-deficient alkenes were efficiently oxidized to chiralcis-diols in yields of up to 98 % and up to 99.9 %eewhen using hydrogen peroxide (H2O2) as oxidant under mild conditions. Experimental studies (including(18)O-labeling, ESI-MS, NMR, EPR, and UV/Vis analyses) and DFT calculations were performed to gain mechanistic insight, which suggested possible involvement of a chiralcis-Fe-V(O)(2)reaction intermediate as an active oxidant. Thiscis-[Fe-II(chiral N(4)ligand)](2+)/H(2)O(2)method could be a viable green alternative/complement to the existing OsO4-based methods for asymmetric alkene dihydroxylation reactions.