Synthesis of cis-Thiiranes as Diastereoselective Access to Epoxide Congeners via 4π-Electrocyclization of Thiocarbonyl Ylides
Won-jin Chung and Jun-Ho Choi show a diastereoselective access to epoxide congeners.
Thiirane can be regarded as a cousin of a much more well-established congener, oxirane. However, while a myriad of synthetic methods – including enantioselective variants – have been extensively developed for oxiranes, thiirane synthesis is considerably underdeveloped, despite the structural similarity and the potential synthetic utility. Professor Won-jin Chung from Gwangju Institute of Science and Technology (GIST, Republic of Korea) said that “all four stereoisomers of stilbene oxide can be easily prepared and are even commercially available. In contrast, few synthetic methods are known for stilbene sulfides, and the processes typically employ stilbene oxides as the precursors.” Most commonly, thiiranes are prepared from the corresponding oxiranes via chalcogen exchange with thiocyanate or thiourea as sulfurating reagents while the stereoselective thiirane synthesis is an even more challenging task. A method for cis-thiiranes is described here. Professor Jun-Ho Choi from the same institute carried out DFT calculations to support the proposed reaction mechanism.