Reaction of Thioketones with (R)‐2‐Vinyloxirane: Regio‐ and Stereoselective Formation of (S)‐4‐Vinyl‐1,3‐oxathiolanes

Abstract

AbstractThe reactions of 4,4'‐dimethoxythiobenzophenone (1), 9H‐xanthene‐9‐thione (2), and adamantane‐2‐thione (3) with (R)‐2‐vinyloxirane [(R)‐6] in the presence of SiO2 in anhydrous CH2Cl2 at 0 °C or room temperature afforded the corresponding 4‐vinyl‐1,3‐oxathiolane derivatives (S)‐7, (S)‐9, and (S)‐11, respectively. The analogous BF3‐catalyzed reactions of (R)‐6 with 1,1,3,3‐tetramethylindane‐2‐thione (4) and 2,2,4,4‐tetramethyl‐3‐thioxocyclobutanone (5) in anhydrous CH2Cl2 at –65 °C or –78 °C yielded the corresponding spirocyclic 1,3‐oxathiolanes (S)‐12 and (S)‐14, respectively. The structures of (S)‐9 and (S)‐12 were established by X‐ray crystallography. In all cases, the nucleophilic thiocarbonyl S atom attacked predominantly C(2) of the Lewis acid‐activated (R)‐2‐vinyloxirane ring with inversion of the configuration through an SN2‐type mechanism. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)