Thioketones mercaptans

Electrochemical reduction of thioketones affords mercaptans under certain conditions. The stereochemistry of this process has not been examined. Reduction of thiocamphor (111) affords a single isomeric thiobomeol 113) but although both isomeric-mercaptans are known compounds, 14>11S>, the stereochemistry of the product was not established n6>. 

The intervention of the vinylic alcohol structure obviously would not be detected in normal kinetic experiments. However, in the sulfur atom case, the sequence may well be arrested at the vinylic mercaptan stage. At lower pressures it is also possible that the vinylic mercaptan further iso-merizes to the thioaldehyde or thioketone structure, which would not be detected, since thiocarbonyls form solid trimers with very low vapor pressures. 

Mercaptans are generally prepared by displacement reactions. However. secondary or hindered mercaptans are more difficult to obtain. The dithiolane cleavage icaction is a convenient in situ generation of thioketones which are known to be reduced with butyllithium to secondary mercaptans by p-hydrogen transfer Table I shows a number of mercaptans prepared from saturated thioketals in 78-90% yields. The aryl example gives lower yields partly because of ring metalation. 

Spot Mercaptans and thioketones markedly catalyze the reaction of sodium azide with iodine with liberation of nitrogen, and this catalyst is used for detection of the sulfur containing compounds. 

Diaryl thioketones are reduced to mercaptans together with minor amounts of desulfurized products. 

Reaction of thioketones with Grignard compds. Tert. mercaptans and sec. thioethers... 

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