Benzo thiophene sulphoxides

Benzo[Z>]thiophen 5-Oxides. - Mild methods for the oxidation of 2,3-dihydrobenzo[Z>] thiophens to the sulphoxide have been developed. The photochemical reactions of various 2- and 3-substituted benzo[ ]-thiophen 1-oxides led to different photodimers. From 3-chlorobenzo[b]-thiophen-2-carboxylic acid 1,1-dioxide, 1,3-oxazinones of biological interest were obtained through cyclization reactions with cyanamides and carbodi-imides. Secondary amines add to 2-phenylbenzo [b] thiophen 1,1-dioxide to give 3-amino-substituted 2,3-dihydro-2-phenylbenzo[b]thiophen 1,1-dioxides. " ... 

Reaction at Sulphur.— The kinetics of the oxidation of benzo[/>]thiophen and its 3-substituted derivatives by perbenzoic acid in dichloromethane at 30 °C have been studied. The rate constants obtained for the first step, the oxidation to the sulphoxide, have been correlated with values, whereas the rate constants for the second step, of oxidation to the sulphone, have been correlated with values. A number of benzo[ft]thiophen and dibenzothiophen derivatives and their sulphoxides have been S- and O-alkylated, respectively, with silver perchlorate and alkyl halides. 5-Methoxydibenzothiophenium perchlorate reacted with amines to give 5-aminosulphonium salts, and with certain carbanions to give zwitterionic compounds such as (394). 

Reaction at Sulphur.—The oxidation of benzo[6]thiophens to sulphoxides by t-butyl hypochlorite has been studied. In the presence of a ruthenium catalyst, dibenzothiophen was oxidized by oxygen to the sulphone. The reactions of benzo[ >]thiophen 1,1-dioxides with various reagents such as amines, amino-alcohols,3-aminopropylsilanes, and aromatic sulphonyl chlorides have been studied. Four detailed papers on the reaction of dibenzophenonium salts with aryl-lithiums have appeared in which the mechanism of ligand exchange was elucidated. " ... 

The reaction of sulphides 59 bearing an ethynyl or a carbomethoxy group a to sulphur with f-butyl hypochlorite in methanol or ethanol gives high yields of the corresponding a-alkoxy sulphides (60) rather than sulphoxides (equation 29). Oxidation of benzo[b]thiophene with t-butyl hypochlorite in t-butyl alcohol at 30-40° gave the corresponding 2-chloro-l-benzothiophen-l-oxide 61 in 45% yield (equation 30). 

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