Cycloaddition Reactions of Thioacylketene Thioacetals and N-Thioacyldithioimidocarbonates

Thioacylketene thioacetals (7) and N-Thioacyldithioimidocarbonates (8) undergo 1,4-cycloaddition reactions with active acetylenes and olefins to give six-membered heterocycles. Tetracyanoethylene behaves in a different way to afford conjugated dienes. In the reactions with diphenylketene and diazo compounds, 7 and 8 undergo different types of reactions; 7 gave products derived from 1,2-cycloaddition to the C=S bond, while 8 afforded 1,4-cycloadducts. Compound 7 was found to be more reactive than 8. The reactivity difference between 7 and 8 is discussed.