Dithiole Carbene Reactions and Bi-l,3-dithioles

The reactions of 4,5-diphenyl-2-piperidino-l,3-dithiole with a wide range of compounds have been described/ Amongst the products, which arise from insertion reactions of the carbenoid species (70 R = Ph), are, for example, (71 R = R = COMe), (71 R = COMe, R = CO Et), (71 R = Et, R = CHO), (72 R = COPh), and (72 R = CH2COCH CHPh). The product obtained with 1-methylbenzothiazolium methosulphate is the electron-rich 

Carbene reactions are also involved when electron-deficient acetylenes are heated with carbon disulphide.Full details have now been published for these addition reactions, in which intermediates of type (70 R = CF, or C02Me) are postulated. Generation of benzyne, from 1-aminobenzotriazole and lead tetra-acetate, in the presence of carbon disulphide, also leads to a 1,3-dithiole carbene, and hence to a variety of complex products.  

One of the most interesting developments in 1,3-dithiole chemistry is the discovery that the complex formed between the 2,2 -bi-1,3-dithiole (74 R = H) and tetracyanoquinodi methane (75) has remarkable electrical properties, behaving like a metal over a large temperature range. This intensely 

A similar highly conducting complex has been obtained from the tetramethylbidithiole (74 R = Me), itself prepared by deprotonation of 

5-dimethyl-l,3-dithiolium perchlorate. Very recently, the tetrakis-methylthio-compound (74 R = MeS) has been reported. The preparation, which is also applicable to the parent dithiole, apparently with advantage, involves conversion of the dithiolethione (76) into the corresponding 2-ethylthio-l,3-dithiolium fluoroborate, bimolecular electrochemical reduction to (77), and a final pyrolysis stage. 

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