Thiols from thiouronium salts

JOC1500,6lAK(l8)i5l, 72AJC985). Both the thiocyanopyrroles from the first method and the thiouronium salts from the second can be hydrolyzed to pyrrole-2-thiols. These compounds are evidently quite sensitive to oxidation so that in situ alkylation is frequently done, resulting in isolation of 2-alkylthiopyrroles as indicated in reactions (213) and (214). 2-Methylthiopyrrole is also obtained in low yield by reaction of the magnesium iodide salt of pyrrole with dimethyl disulfide (6lAK(l8)i5i). 

The value of thiourea for the preparation of thiols is that on reaction with alkyl halides,271 mixtures of hydrogen bromide and alcohols,272 or suitable aromatic273 or heterocyclic halides274 it readily yields S-alkyl- or S-aryl-thiouronium salts, from which the thiols are usually obtained in good yield by alkaline hydrolysis or by aminolysis with high-boiling, strongly nucleophilic... 

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