Asymmetric Sulfenamide Oxidation Enabled by Bisguanidinium Dinuclear Oxodiperoxomolybdosulfate: Reactivity and Mechanistic Insights
Yuanyuan Zhang, Hongjie Cao, Shengnan Wei, Yongxin Li, Libo Wang, Lili Zong
Abstract
Enantioenriched sulfinamides have emerged as versatile building blocks for the synthesis of biologically interesting organosulfur compounds bearing sulfur stereocenters. Therefore, the development of catalytic asymmetric methodologies to access chiral sulfinamides is in demand, especially for these without the need for an inert atmosphere or accurate temperature control. We now report chiral bisguanidinium and molybdate cocatalyzed asymmetric oxidation of prochiral sulfenamides with hydrogen peroxide at room temperature. A variety of chiral alkyl-, aryl-, and heteroaryl sulfinamides were smoothly obtained in good to high yields and enantioselectivities under simple conditions with a low loading of bisguanidinium (0.05–0.2 mol %). Further stereospecific transformation of chiral sulfinamides to other sulfur-stereogenic compounds such as N -free sulfinamide was also achieved. Mechanistic studies suggest that the interplay of ion pairing and hydrogen bonding interactions between bisguanidinium dinuclear oxodiperoxomolybdosulfate, sulfenamide substrate, and Brønsted acid additive is essential to the realization of high reactivity and stereocontrol.