Benzodithioles reduction

The S—S bond of 1,2-dithioles is easily cleaved by reduction and, for example, dithioles (249) can be converted into acyclic methyl dithiolates (251) by electrochemical reduction, followed by alkylation of the intermediate dianions (250). Benzodithioles (252) are more stable and the heterocycle survives reduction with zinc and trifluoroacetic acid, although the exocyclic double bond is saturated to give 2-al-kyldithiolanes (253). ... 

Benzodithioles 197 (dienophiles) were employed in aza-Diels-Alder reactions with A -arylimines 198 as a versatile approach to tetrahydroquinolines 199. Subsequent transformations of the latter under reductive and oxidative conditions provided an access to 2,3-disubstituted tetrahydroquinolines 200, inaccessible through the conventional [4+2] cycloaddition strategy, and also to 2,3-dihydro-4-quinolones 201 and 4-quinolones 202 (Scheme 23) <20020L4411>. 

The chemistry of 2-alkoxy-l,3-benzodithioles has been reviewed. A new route for the reduction of carboxylic acid derivatives is provided by their conversion into... 

Very recently, Cozzi et al. successfully demonstrated the application of this methodology for the a-alkylation of the formyl group to enohzable aldehydes. This was achieved by a reaction of benzodithiolylium tetrafluoroborate (a stabilized carbenium ion) in the presence of several different substituted imidazolidin-4-ones [48]. After reductive removal of the benzodithiol group access to chiral a-branched primary alcohol is given. Using this method optically pure arundic acid is obtained by a three-step synthesis. 

No evidence could be obtained for the formation of 2ff-benzo[i>]thiet or its valence tautomer by irradiation of 3/f-l, 2-benzodithiole l,l-dioxide. Naphtho-[l,8-6c]thiet (58) has been prepared and its 5-oxide, and S -dioxide, have been obtained by oxidation with m-chloroperoxybenzoic acid. All three compounds react with lithium aluminium hydride to give ring-opened products as the result of hydride attack on sulphur. After reduction and methylation, (58) gave the methyl sulphide (59), and the 5-oxide gave bis(a-naphthyl) disulphide (75%) together with (58) (6%) and the corresponding sulphone (4%), which was the major product (85%) from the 55-dioxide (Scheme 8). Thiets are believed to be... 

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