The Reaction of Oxiranes with Carbon Disulfide under High Pressure

Abstract

Abstract The reaction of 2,2-dimetyloxirane with carbon disulfide in the presence of triethylamine was accelerated under high pressure to give 5,5-dimethyl-1,3-oxathiolane-2-thione in a high yield, while 2-hexyloxirane under the same reaction condition formeds 4-hexyl-1,3-dithiolane-2-thione (2b) as the main product and 5-hexyl-1,3-oxathiolane-2-thione (1b) as a minor product. A feasible mechanism for this formation is that 1b and 2-hexylthiirane (4b) are produced in the first stage of reaction, and that 2b is then formed by the reaction of 1b or 4b with carbon disulfide. In reactions of a variety of oxiranes with carbon disulfide, 1,3-dithiolane-2-thiones were obtained in high yields under 800 MPa at 100 °C within 20 h. Concerning the effect of substituents in oxiranes, the selectivity for product 2b is in the decreasing order; 2-phenyl->2-methyl->2-ethyl->2-hexyl->2,3-tetramethylene->2,2-dimethyl->2-(chloromethyl)-. Tertiary amines, such as N,N-dimethylethylamine, pyridine, and N-methylmorpholine, serve as good catalysts for the reaction.