Dithiolylium iodide

C3S2 s s — — — l,2-Dithiolane-4-carboxylic acid 3-phenyl-l,2-dithiolylium iodide 4-methyl-1,2-dithiole-3-thione ... 

The 2-(methylthio)-1,3-dithiolylium iodide can be prepared by a published procedure17 or purchased commercially (Strem Chemical Co., Danvers, MA). 

When the addition is complete, anhydrous diethyl ether (about 200 mL) is added. The near-white salt, 1,3-dithiolylium tetrafluoroborate,12 is collected on a Buchner funnel, washed with anhydrous diethyl ether, and dried under nitrogen. The 1,3-dithiolylium tetrafluoroborate (28 g, 0.15 mole) from the precious step is dissolved in acetonitrile (100 mL) in a 500-mL Erlenmeyer flask. While the solution is stirred magnetically at 0°, triethylamine is added until the formation of yellow crystals becomes obvious (about 50 mL). Another quantity of triethylamine (about 10 mL) is added and stirring is continued for 10 minutes. Water (approximately 300-400 mL) is added to precipitate the product, which separates as yellow-orange crystals. The solid is collected on a Buchner funnel, washed with water, and dried under nitrogen. The yield of crude product is 15.0 g (0.0736 mole), which corresponds to an 82% overall yield based on the starting 2-(methylthio)-l,3-dithiolylium iodide. 

X-Ray structure determinations for 1,2-dithiolylium salts (4) (80MI43100) showed S—S bond distances of 2.02 A. For 1,2-dithiolylium iodides (4 X = I), charge transfer between the cation and iodide was found. 3,5-Diamino-l,2-dithiolylium ions (8) and derivatives showed long S—S bonds ( 2.07 A), indicating substantial iminium character, i.e. from structures of type (8a). The mesoionic l,2-dithiolylium-4-olates (7) have typical dithiolylium bond distances (78AJC297) and are best represented as shown. 

DithiafuIvaIene (197) can be obtained by reaction of the 1,3-dithiolylium iodide (195) with two moles of the sodium salt of cyclopentadiene in THF (65CB2825). 

Also, interesting 7,10-dithiasesquifulvalene-l, 2-quinone derivatives (204) can be obtained by condensation of 2-methylthio-l,3-dithiolylium iodide with a-tropolone derivatives (203) (81CL805). With j8-tropolone (205) and 1,3-dithiolylium iodide (195) in the presence of pyridine the reaction proceeds with formation of the 7,10-dithiasesquifulvalene-1,6-quinone (206) (77CL287). 

Another nucleophilic displacement of the methylthio group is observed with indole as a reactant. Heating indole with the 2-methylthio-l,3-dithiolylium iodide (195) at 50 °C in acetonitrile produces the salt (210) in 58% yield. Subsequent treatment of (210) with l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a base forms the fulvene derivative (211) in quantitative yield (80BCJ1661). 

Also IV-ethyl-l-naphthylamine reacts with 2-methylthio-1,3-dithiolylium iodide (195) to form the 1,3-dithiolylium salt (212) which can be dehalogenated with base to the quino-methidimine derivative (213) (81CC565). 

Reduction of 2-unsubstituted 1,3-dithiolylium salts, e.g., 389 (R = H), with zinc or hexacarbonyl-vanadate leads to dimerization affording 390 the reduction of 2-methylthio-dithiolylium iodide 389 (R = SMe) with zinc in the presence of bromine, however, gives TTF 391. 

The reaction of 3-(methylthio)-3Tf-l,2-dithiolylium iodide (51) with 1,3-di-aminopropan-2-ol gives bis(enaminodithioester) isomers 52 in an isomeric mixture with 60% combined yield (Eq. 18) these isomers are potential tetra-dentate ligands [46]. 

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