Benzo-l,2-dithiole-3-thione

Some years later, the first stable thiocarbonyl ylides 9 and 10 were prepared by the reaction of thiourea with cyano-substituted oxiranes (19,20) or by addition of Rh-di(tosyl)carbenoid to benzo-l,2-dithiole-3-thione (21), respectively. Enhanced stability and the low reactivity of 9 and 10, which enables their isolation in crystalline form, results from the push-pull substitution at the two termini [cf. also (22)]. Another class of stable thiocarbonyl ylides that are also able to afford [3 + 2]-cycloaddition products are the mesoionic 1,3-dithiole-4-ones of type 11 (23,24). 

Finally, we turn to sulfur-containing species. Many indane derivatives may be suggested. However, there are only a few for which the enthalpy of formation has been determined phenylene trithiocarbonate (benzo-l,3-dithiole-2-thione) (X = Z = S, Y = CS) (XI), the isomeric benzo-l,2-dithiole-3-thione (X = Y = S, Z = CS) (X) [50],... 

Benzo-l,2-dithiole-3-thione+2C2H6 — oC6H4(CH3)2 + CH3C(S)SSCH3 (21)... 

The reduction of benzo-l,2-dithiole-3-thiones (77b) to various polythiols (74ACS(B)827, 63LA(661)84) may be accomplished by lithium (78BEP867155), lithium aluminum hydride, or by catalytic hydrogenation, and Raney nickel hydrodesulfurization gives products by complete elimination of sulfur (B-66MI43100). 

Benzo-l,2-dithiole-3-thione (77b) also reacts, but the monoadducts corresponding to (95) have o-thioquinone methide structures (cf. structure 104) and form diadducts rapidly. The use of dehydrobenzene (benzyne) gives 2-thioacylmethylenebenzo-l,3-dithioles (95 R3, R4 = (CH=CH)2). 

For alkanes, alkenes and their aryl derivatives, direct sulfurization gives thiones (3b). Typical examples are the preparation of 4-methyl- (10), 5-(4-methoxyphenyl)- (129) and 4-phenyl-l,2-dithiole-3-thiones (71) and benzo-l,2-dithiole-3-thione (77b) (Scheme 22) (B-66MI43100). 

The readily accessible enamines react with carbon disulfide and sulfur under mild conditions to produce l,2-dithiole-3-thiones (3b) via 3-amino dithioacids (Scheme 24), The nucleophilic character of the enamines is necessary for the initial reaction and to activate the sulfur (from Sg) for further insertion (67AG(E)294). Modified procedures produce other heterocycles. The yields of thiones (3b) may be low but this versatile reaction produces thiones that may be otherwise difficultly accessible, especially by direct sulfurization procedures, e.g. 1-morpholinocyclohexene may be converted into tetrahydrobenzo-1,2-dithiole-3-thione (142) in 40% yield. By contrast, direct sulfurization of 1-methylcyc-lohexene gives benzo-l,2-dithiole-3-thione (77b). Even dihydronaphtho-l,2-dithiole-3-thione (143) may be made by this procedure, although this compound may be dehydrogenated readily by sulfur at 220 °C. 

The required C3S unit also exists in 2-thio derivatives of benzoic acid. Thus, thionation of diphenyl disulfide-2,2 -dicarboxylic acid gives benzo-l,2-dithiole-3-thione (37b). This approach can be also applied to thienodithioles and to dithiolopyridines <82AHC(3l)63>. In a conversion of thiosalicylic acid to benzo-l,2-dithiole-3-thione, the extra sulfur atom is provided by thiolacetic acid <920PP488>. The necessary units also appear in some palladium complexes, which by treatment with thiocyanate give benzo-l,2-dithiolium salts and other fused dithioles (Equation (10)) <90JCS(Pl)288l>. 

Chloro- benzisothiazoles (153) or benzisothiazolium (154) salts react with thiolacetic acid to give 1,2-dithioles, and benzo-l,2-dithiole-3-thiones are formed from benzisothiazoline-3-thiones with hydrogen sulfide. An isothiazoline-3-thione (155) reacted with phenylethyne to form what may... 

Benzo-l,2-dithiole-3-thione (77b) reacts with lithium in THF to produce a complex which is useful in the preparation of lithium hydrides (78BEP867155). Various 3-(4-dimethyl-aminophenyl-l,2-dithiolylium salts (175) and other dithiolylium salts function as dyes for polyacrylonitrile and have been proposed as sensitizers for organic photoconductors (64USP3158621, 66USP3299055, 71USP3530145, 71USP3575968). 

The o-thioquinone methide (39), generated by the photoreaction of benzo-l,2-dithiole-3-thione with olefins, dimerizes to give a head-to-head dimer. Further... 

Thiol anhydrides (RCO)2S are formed on reaction of RC(S)OSiR3 with RC(0)C1, and the salts RCS2 R2NH2+ are oxidized to [RC(S)S]2 by RSO2CI. Coyle has reviewed the photochemical properties of thioesters. Compound (172) is split into PhC(0)SH and PhCMe=CHa on photolysis." Ethyl thiono-acetate yields a complex mixture of products on u.v. irradiation, from which 2,3-diethoxybut-2-ene and 2,3-diethoxybut-l-ene can be isolated. Photolysis of benzo-l,2-dithiole-3-thione in the presence of alkenes yields the blue compound (211). ... 

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