Studies on Organic Sulfur Compounds. X. The Reactions of Alkoxycarbonyl Isothiocyanates with prim-α-Acetylenic Alcohols

The reactions of alkoxycarbonyl isothiocyanates and prim-α-acetylenic alcohols afford N-alkoxycarbonyl-O-acetylenyl thiocarbamates, N-alkoxycarbonyl-S-allenyl thiolcarbamates and 4-alkylidene-2-alkoxycarbonylimino-1, 3-oxathiolanes. However, the reaction patterns are dependent on the substituents on the 3-positions of α-acetylenic alcohols: 3-Phenyl-2-propyn-1-ol (40) react smoothly with the isothiocyanates to give 1: 1 adducts which cyclize immediately to 4-benzylidene-1, 3-oxathiolanes (42). 2-Butyn-1-ol (36) reacts slowly with the isothiocyanates to afford N-alkoxycarbonyl-O-2-butyn-1-yl thiocarbamates (37), but these compounds (37) cyclize hardly to 4-ethylidene-1, 3-oxathiolanes (39) even in the presence of a base. In the case of 2-propyn-1-ol (19), N-alkoxycarbonyl-O-2-propyn-1-yl thiocarbamates (24), N-alkoxycarbonyl-S-allenyl thiolcarbamates (25) and 2-alkoxycarbonylimino-4-methylidene-1, 3-oxathiolanes (26) are obtained. Furthermore, the cyclization mechanisms of α-acetylenyl thiocarbamates (45) were confirmed by using N (D)-O-(2-propyn-1-yl)-N-isopropoxycarbonyl thiocarbamate (43).