Dithiocarboxylation carbanions

Carbon disulphide should not be used as the solvent for alkylation of fS-diketones, as the carbanion reacts preferentially with the solvent to generate the dithiocarboxyl-ate derivative, which undergoes mono- and dialkylation (Scheme 6.9) [95]. Ketene thioacetals have also been isolated from acetophenones (60-80%) and cyclopenta-diene (80%) using an ultrasound technique in carbon disulphide [96] and, in a similar manner, pyrazol-5-ones form pyrazole-4-dithiocarboxylic esters [97]. 

Dithiocarboxylation of Arenes and Carbanions under Formation of Carbon-Carbon Bonds... 

Under basic conditions, carbanions derived from thiones, thionoesters, or thioamides react with carbon disulfide to give dithiocarboxylic acids, or derivatives that can be cyclized to 1,2-dithioles <76BCJ3128, 80LA483>, For example, the thioindoxyl (130) forms the dithioloindole (131) <82AHC(3i)63>. The 3-aminocarbanions (132) give bis-l,2-dithiol-3-ylidenes (9), probably via 1,2-dithiole-3-thiones (2a) <82ZOR274>. 

Addition of carbon disulfide to the carbanion, generated from the allene (13), and intramolecular addition of the dithiocarboxylate sulfur to the triple bond gives the compoimd (14) (Scheme 5) <85TL5I31>. Metallation of the diynes (15), followed by the successive addition of carbon disulfide, Bu OH, and HMPT, affords thienothiophenes (17) in reasonable yields (Scheme 6), and the use of the sulfides (18) as the starting material produces the thienodithiins (19) (Equation (3)) when R is TMS in the starting compounds, the unsubstituted parent compounds are obtainable in these cases since desilylation probably takes place at some intermediate stage <83CC1056>. 

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