1.3- Dichlorobenzo thiophene

The sulfones of 3-methyl-, 3-methoxy-, 3-dimethylamino-, and 3-piperidinobenzo[6]thiophene yield only sulfur dioxide and intractable tars on being heated in inert solvents, whereas 2-bromo- and 2,3-dichlorobenzo[6]thiophene-l,1-dioxide are extremely stable to... 

The reaction of 2,3-dichlorobenzo T] thiophene with bromoethene has been described and a mixture of isomeric adducts was obtained... 

A number of examples of photocycloaddition to sulphur-containing heterocycles have been reported. 2,3-Dichlorobenzo(b]thiophene (226) undergoes [ 2 + 2] benzophenone-sensitized photoaddition to vinyl bromide to give the stereoisomeric adducts (227). A potentially more useful cycloaddition has been described for 4-methoxy-l-thiocoumarin (228) which with isobutene, for example, affords the adduct (229). The structures assigned to adducts of... 

Reactions of 2,3-dichlorobenzo [b] thiophene 1,1-dioxide 123 with nitrogen and oxygen nucleophiles produce substitution products, 124 and 125, at the 3-position because the addition of nucleophiles takes place exclusively at that position (Scheme 70) [196-198]. However, in the case of 2-bromo-3-phenylben-zo [ b] thiophene 1,1 -dioxide 126, nitrogen nucleophiles added to carbon 2 to give compounds 127 (Scheme 71) [194]. 

Reactions of Benzo[b] thiophens. Photochemical cycloaddition of 2,3-dichlorobenzo[fe] thiophen with vinyl bromide under benzophenone-sensitized conditions gave a mixture of isomers of (232) in the presence of free-radical inhibitors. The products from the photocyclization of DMAD with substituted benzo [h] thiophens are (233) or (234), depending upon the... 

Nucleophilic substitution in 2,3-dichlorobenzo[b] thiophene 1,1-dioxides takes place preferentially in the 3-position.352 2-Bromobenzo[i>]thiophene 1,1-dioxide is converted into the 3-bromo isomer by KNH2-NH3215 it is well established that a 2-bromine atom is replaced by a nucleophile with rearrangement to give the 3-substituted product.1 A 3-chloro substituent, activated by an adjacent ester or ketone function, is very readily replaced, and cyclization can often take place to form an additional heterocyclic... 

The sensitized photochemical [2 + 2] cycloaddition of halogenated alkenes to benzo[6]thiophene has been explored further. With 2,3-dichlorobenzo[6]thiophene as the substrate, addition of vinyl bromide gives a 1 1 mixture of two stereoisomers. It has been concluded that the reaction proceeds... 

Dichlorobenzo[c]thiophene, bright yellow crystals, mp 54°C, was prepared from phthaloyl dichloride [95] ... 

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