ALPHA-THIOTETRONIC ACIDS .2. REACTIONS OF GAMMA-ALKYLIDENE-ALPHA-THIOTETRONIC ACIDS

The alpha-thiotetronic acid 1 reacts with amines predominantly with ri ng opening to give polyfunctionalized ketones (2) which readily cycliz e to alpha-tetramic acid amides (4a, b). The reaction of alpha-thiotet ronate 6 with nucleophiles is more complex, leading to either an open- chain derivative (8) or formation of an alpha-thiotetronic acid amide (3b) or an alpha-tetramate (4f). Treatment of 6 with sodium sulfide in air furnishes the salt of the 1,2-dithiole 10. The dibrominated alpha -thiotetronate 13a reacts with N and S nucleophiles predominantly by s ubstitution, leading finally to the bisthiolactones 14 or the thieno-1 ,2-dithioles 17.