Benzo thiepin, 2,3-dihydro

Dihydro-1-benzothiepin is converted into 2,3-dihydro-l-benzo-thiepin 1-oxide with sulfuryl chloride in 79% yield or with sodium periodate in 77% yield (equation 562) [5%]. 

According to the Hantzsch-Widman system, the seven-membered unsaturated hcterocyclc with one sulfur atom is named thiepin (1). The three different benzothiepins are assigned by the position of sulfur 1-benzothiepin (2), 2-benzothiepin (3) and 3-benzothiepin (4). Of the four possible dibenzothiepins only dibenzo[6,r/]thiepin (5) and dibenzo[A,/]thiepin (6) are of importance for synthesis, while the other two isomers, which contain unfavorable o-quinoid structures, exist mainly as the stable dihydro compounds, i.c. 5,7-dihydrodibenzo[c,t ]thiepin (7) and 6,1 l-dihydrodibenzo[6,c ]thiepin (8). Benzannulation over all double bonds results in tri-benzo[6,(7,/]thiepin (9). 

Benzo[e]thieno[3,2- ]thiepin-10(5Ef)-one 388 can be smoothly reduced with sodium borohydride to the corresponding alcohol, which forms the chloro substituted compound under standard treatment with thionyl chloride (1991CPB2564). Dihydro derivatives of pyrrolo-benzothiazepine 377 have been reported starting from ketone 373 by a carbonyl reduction, bromination and amination sequence (Scheme 76, Section 5.1.1 (1998JMC3763, 2002JMC344, 2004JMC143)). 

Carbon-carbon bond formation by Friedel-Crafts reactions was a versatile procedure for benzo- and dibenzothie-pines. Some new methods to synthesize thiepine rings by Friedel-Crafts-type reactions have been reported. Carbon-sulfur bond formation has been used for dihydro-, tetrahydrothiepines, and thiepanes. New cyclization methods involving carbon-sulfur and carbon-carbon bond formation have been added. 

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