SO2-extrusion of an 8-thiabicylo[3.2.1]octa-2,6-diene 8,8-dioxide and rearrangement of the resulting cycloheptatriene

The reaction of 3,4-di-tert-butylthiophene 1-oxide (8) with tetrachlorocyclopropene provided 6,7-di-tert-butyl-2,3,4,4-tetrachloro-8-thiabicylo[3.2.1]octa-2,6-diene 8-oxide (10), which was oxidized to the corresponding 8,8-dioxide 16 by m-chloroperbenzoic acid. The thermolysis of 16 in refluxing chlorobenzene, xylene, or octane gave 5-tertbutyl- 1, 2-dichloro-3-[(1, 1-dichloro-2,2-dimethyl)propyl]benzene (18) with extrusion Of SO2 and 2-tertbutyl-4,5,6-trichloro-9,9-dimethylbicyclo[5.2. 0]nona1, 3,5-triene (19) with extrusion Of SO2 and HCl in 73- 78% combined yields. on the other hand, the thermolysis of 16 in the presence of triethylamine gave 19 as the sole product in 98% yield. A mechanism that involves the initial formation of 4,5-di-tert-butyl- 1, 2,7,7tetrachlorocycloheptatriene (17) is proposed to explain the observed products. (c) 2005 Wiley Periodicals, Inc. Published online in Wiley InterScience.