Reactions of acetylenes, possessing bulky alkyl substituents, with S2Cl2. Unexpected formation of α-oxothioketones, thiirene 1-oxides, and 1,2-dithietes

The reaction of di-t-butylacetylene with S2Cl2, followed by purification with silica-gel column chromatography, gave 2,2,5,5-tetramethyl-4-oxo-3-hexanethione (4a) (37%) and 2,3-di-t-butylthiirene 1-oxide (5a) (10%), which were formed by hydrolysis of the initial product, 2,3-di-t-butyl-2,3-dichloroepisulfide (3a). The same work-up of the reaction mixture of di(1-adamantyl)acetylene with S2Cl2 provided 2-oxoethanethione (4b) (4–33%), thiirene 1-oxide (5b) (8–27%) and 1,2-dithiete (9b) (3–21%). The reaction of 2,2,5,5,6,6,9,9-octamethyl-3,7-decadiyne (1c) with S2Cl2 furnished a 4H,5H-thiepin (12) as the sole product in 99% yield.