3- Thiabicyclo heptenes

The first attempted synthesis of a benzo[ ]thiepin derivative was the solvolysis of 7,7-dichloro-3,4-benzo-2-thiabicyclo[4.1,0]heptene (19)20). Unfortunately, the reaction of 19 in hot quinoline led to 2-chloronaphthalene which suggested the reaction mechanism as shown below. In the case of the reaction of l,l-dichloro-7b-ethoxy-... 

Cycloaddition of thioacylsilanes 1 with open-chain dienes and cyclopen-tadiene represents an easy and high-yielding approach to silyldihydrothiopyrans 18 and silylated thiabicyclo[2.2.1]heptenes 199,16,32,33 (Scheme 13). 

Cycloaddition with Alkenes. Tetrachlorothiophene dioxide (TCTD) undergoes a [4 + 2]cycloaddition with olefins to give an unstable 7-thiabicyclo[2.2.1]heptene dioxide which rapidly extrudes SO2 in a cheletropic reaction yielding a 1,2,3,4-tetrachloro-cyclohexa-1,3-diene (eq 1). The primary product has never been observed but it seems plausible as with 3,4-dichlorothiophene dioxide the analogous 7-thiabicyclo[2.2.1]heptene dioxide can be obtained. The broad scope of this reaction is given in the pioneering paper of Raasch. ... 

Reactions of tetrasubstituted thiophene 1-oxides with allenes afford thiabicyclo [2.2.1]heptene 1-oxides of types 40 and 41 along with aromatized products but in... 

The other methodology to increase the reactivity of thiophenes is reduction of aromaticity by oxidation of sulfur to thiophene S-oxide (Scheme 28) [46]. Reactions of thiophene S-oxides 115 with cyclopropenes 116 afforded under high-pressure 7-thiabicyclo[2.2.1]heptene S-oxides 117 in moderate-to-high yields. 

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