Regio- and Stereoselective Synthesis of Dithiocarbonates under Ambient and Solvent-Free Conditions

Herein, we report on the utilization of readily available lithium tert-butoxide as an efficient catalyst for the addition of carbon disulfide to terminal and internal epoxides under ambient conditions. Notably, the reaction proceeds regio- and stereoselectively. By applying the optimized conditions, 14 terminal and internal epoxides were converted. The desired cyclic dithiocarbonates were isolated in yields up to 95% after simple filtration over silica. NMR spectroscopy experiments to identify the mode of activation were performed, and they indicated activation of carbon disulfide by the catalyst. The reaction of cis-2,3-butyleneoxide gave only the trans-dithiocarbonate, whereas the conversion of (R)-propylen oxide gave the respective thiocarbonate stereoselectively as one enantiomer (>99%ee) in 87% yield.