Grignard with disulfides

Early work [10] suggested that reactions of Grignard reagent with disulfides resemble those of organolithium compounds ... 

Carbon disulfide reacts with Grignard reagents to prepare the corresponding dithiocarboxyHc acids ... 

These are strong, unstable acids. Oxidation to disulfides takes place readily. Several methods have been used to prepare the dithio acids (I), the most useful of which is the reaction of CS with a Grignard reagent (27). 

Dithioacids have been generated from carbon disulfide with Grignard reagents or alkyl lithium at 0 °C. Subsequent treatment with sulfonamide in situ gives the corresponding both aliphatic as well as aromatic thioamides in 70-90% yields (Scheme 10).31... 

The free dithiocarboxylic acids can be isolated, but their salts are preferred. In some cases their metal complexes can be prepared directly by insertion of carbon disulfide into metal-carbon bonds. Thus, the reaction of Grignard reagents, RMgX, with CS2, followed by acid treatment gives the dithiocarboxylic acids RCSSH and metal complexes in good yields.311... 

Oxidation, of Grignard reagents with peresters, 41, 91 43, 55 of 2-hydroxy-3-methylbenzoic acid to 2-hydroxyisophthalic acid by lead dioxide, 40, 48 of indene, 41, 53 44, 63 of indolepyruvic add, 44, 66 of methyl disulfide to methanesul finy 1 chloride by chlorine, 40, 62 of 2-exo-norbomyl formate by chromic add, 42, 79... 

Benzofuranyl)butanoic acid readily forms the acid chloride, and this undergoes intramolecular Friedel-Crafts acylation on treatment with tin(IV) chloride in carbon disulfide at room temperature, providing 1,2,3,4-tetra-hydro-l-dibenzofuranone (54%). " This intermediate has been converted to dibenzofuran by lithium aluminum hydride reduction and subsequent dehydrogenation, to 1-methyldibenzofuran by Grignard reaction and dehydrogenation, and to 1-dibenzofuranol by reaction with iV-bromosuccinimide and subsequent dehydrobromination with pyridine. 

It must be noted that while the reaction of Grignard reagents and that of cuprates with carbon disulfide are generally well controlled, the reaction of lithium reagents has been only successfully reported in a few particular cases [150]. The reaction is quite complex in the general case and a clarification necessary. 

New routes have been designed by Katritzky and co-workers using ben-zotriazole derivatives. Alkylation of primary thioamides has been achieved on the nitrogen atom using an aldehyde as a source of the alkyl group [42]. A variety of thioamides is accessible by a one pot reaction of a Grignard reagent with carbon disulfide (in THF), followed by treatment with benzo-triazole triflate and aminolysis of the activated thiocarbonyl intermediate [43, 44]. 

A convenient reaction of organolithium with easily available thiuram disulfides was reported by Gronowitz et al. [45], and the reaction of Grignard reagents with N,AT-dimethylthiocarbamoyl chloride was found [46] to be nicely catalysed by NiCl2(dppe) to afford thioamides. An analogous route with palladium[II] catalysis allowed Hartke et al. [47] to prepare a number of interesting a-acetylenic thioamides. 

Dithioesters can be made by a method that would seem odd if you thought only of ordinary esters. Organolithium or Grignard reagents combine well with carbon disulfide (CS2—the sulfur analogue of CO2) to give the anion of a dithioacid. This is a much more nucleophilic species than an ordinary carboxylate anion and combines with alkyl halides to give dithioesters. 

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