3- Methylthio-l,2-dithiolium ions

Chloro- or 3-bromo-l,2-dithiolium ions react with hydrogen sulfide or methanethiolate anions giving l,2-dithiole-3-thiones or 3-methylthio-l,2-dithiolium ions, respectively (Scheme 16). °... 

As shown in Scheme 21, aliphatic primary amines may react in three ways with 5-aryl-3-methylthio-l,2-dithiolium ions. ° The products are 49, a 5-aryl-l,2-dithiole-3-thione, by sulfur demethylation 50, a methyl 3-alkylamino-3-aryldithioacrylate, by nucleophilic attack on carbon 5 and/or 51, a 2-alkyl-5-arylisothiazoline-3-thione, by nucleophilic attack on carbon 3. 

Aryl-3-methylthio-l,2-dithiolium ions react with secondary aliphatic amines. As shown in Table I, the following compounds may be obtained in various yields 5-aryl-l,2-dithiole-3-thione (56), by sulfur demethylation methyl 3-aryl-3-(dialkylamino)dithioacrylate (57) and A, A-dialkyl-5-aryl-1,2-dithiol-3-iminium ion (58). 

Methylthio-l,2-dithiolium ions having no aryl substituent at position 5 react with primary and secondary amines to give 3-aminodithioacrylic esters (Eq. 21). Simultaneously, demethylation to the corresponding 1,2-dithiole-3-thione may occur to a large extent. By reaction of two amine molecules instead of one, 3-aminothioacrylamides are sometimes obtained. 

In the presence of acetic acid and pyridine, 5-phenyl- or 5- eri-butyl-3-methylthio-l,2-dithiolium ions have been reacted with cyanoacetone to give, in the usual way, an a-(l,2-dithiol-3-ylidene) ketone. A similar reaction has been observed with 4-hydroxy-6-methylpyran-2-one and with 4-hydroxy-coumarin (Eq. 23). In the same way, 4-hydroxy-6-methylchromene-2-thione and 3-methylthio-5-phenyl-l,2-dithiolium cation gave the fused trithiapentalene 59. ... 

Similarly, sodium enolates of 3-oxo-3-phenylpropanal react with 5-aryl-3-methylthio-l,2-dithiolium ions. Sometimes only one product can be characterized in other cases a mixture of the two possible geometric isomers (60 and 61) is obtained. ... 

Aryl- or 5-tert-butyl-3-methylthio-l,2-dithiolium ions react with anthrone in the presence of pyridine to give the quinonoid structure 63, A similar reaction, leading to 64, is observed with sodium 2,6-dimethyl-phenate. ... 

Similarly, both the 2-phenyl- and the 2,4-diphenylimidazolate anions give, with 3-methylthio-5-phenyl-l,2-dithiolium ion, dithiadiazafulvalenes. 4-Aryl-3-methylthio-l,2-dithiolium ions react with AT-alkylarylamines, to give methyl 2-aryl-3-(4-alkylaminophenyl)dithioacrylates (Eq. 24). ... 

Methylthio-l,2-dithiolium ions react with ethylidenemalononitrile in an acetic acid-pyridine mixture (Eq. 25). ... 

The use of dithiynes for the preparation of thienothiophenes is exemplified by four types of reactions. For example, 3-methylthio-l,2-dithiolium ions 102 react with... 

Thioacetic acid reacts with 3-chloro-l,2-dithiolium ions to give the corresponding l,2-dithiole-3-thione. The mechanism shown in Scheme 17 has been suggested.Hydroselenolysis of 3-methylthio-l,2-benzodithiolium ion gives the corresponding l,2-dithiole-3-selone. ... 

With aromatic primary amines, the above 5-aryl-3-methylthio cations give the corresponding JV-arylimine (52).142,143 similarly, N-alkylarylamines lead to a 3-(A -alkylarylamino)-5-aryl-l,2-dithiolium ion (53), which can also be considered as an iminium ion (54). In position 5, a 2-arylvinyl substituent has a similar eflFect (Eq. 20). 

Similarly, both the 2-phenyl- and the 2,4-diphenylimidazolate anions give, with 3-methylthio-5-phenyl-l,2-dithiolium ion, dithiadiazafulvalenes. ... 

An important route to 1,4,2-dithiazines (136) involves the ring expansion of 1,3-dithiolium salts (76JPR127). Thus reaction of 2-methylthio-l,3-dithiolium salts with azide ion gives an unstable intermediate which rapidly loses nitrogen to give 1,4,2-dithiazines (Scheme 33). It is not known whether the reaction involves a nitrene intermediate or whether the [1,2] shift is concerted with loss of nitrogen. The latter possibility seems more likely. 

By electrolytic reduction of 2-ethylthio-4,5-bis(methylthio)-l,3-dithiolium ion, a dimer 144 is obtained. It gives a TTF derivative on pyrolysis. ... 

---