Abstract
By thermal decomposition of 1,1,3,3-tetramethyl-5-thia-7,8-diazaspiro[3.4]octan-2-one (1), 2,2,4,4-tetramethyl-3-thioxocyclobutanone S-methylide (2) was generated as an intermediate. This reactive 'thiocarbonyl ylide‘ was trapped by protic agents such as alcohols, NH- and SH-acidic compounds to give 1,3-adducts of the acetal type. In a mixture of methanol and ammonia, the spiroheterocycle 1 was deprotonated and competitive ring opening of the 2,5-dihydro-1,3,4-thiadiazole and the cyclobutane ring occurred to give the hydrazono derivative 7 and the 1,3,4-thiadiazole 8, respectively. Surprisingly, 2 was intercepted by maleimide in a 1,3-dipolar cycloaddition.
Mloston, Grzegorz