Thio‐ and Dithioesters as Dipolarophiles in Reactions with Thiocarbonyl Ylides

Abstract

Abstract The thiocarbonyl S ‐methylides 3a – c , generated in situ by thermal decomposition of the corresponding 2,5‐dihydro‐1,3,4‐thiadiazoles, undergo [3+2] cycloadditions with diphenyl trithiocarbonate ( 5a ) to give 1,3‐dithiolanes. The regioselectivity of the reaction of the cycloaliphatic dipoles 3b and 3c is reversed in comparison with that of the aromatic 3a . A mixture of both regioisomeric cycloadducts is formed in the reaction between 3b and methyl dithiobenzoate ( 6a ), whereas only one regioisomer is obtained with thiophthalide ( 7 ). Dialkyl phosphonodithioformates 8 are shown to be efficient C=S dipolarophiles in reactions with thiocarbonyl S ‐methylides 3a – 3d , affording 1,3‐dithiolane‐4‐phosphonates. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)