Cleavage of α,β‐unsaturated Sulfides, Alkyl Cycloalkyl Sulfides AND Cycloalkanone Dialkyl Dithioacetals with Alkali Metals in liquid Ammonia

Unsaturated thiols having the system ‐C=C‐SH can be obtained by cleavage of the corresponding alkyl sulfides ‐C=C‐SR with alkali metals in liquid ammonia and acid hydrolysis after evaporation of the ammonia. Cycloalkanone dimethyl dithioacetals (CH2)nC(SCH3)2 give cycloalkanethiols (CH2)nC(H)(SH) (n = 2, 4, 5, 6) on treatment with 4 equivalents of alkali metal. Alkyl cycloalkyl sulfides (CH2)nC(H)(SR) (R = CH3 or C2H5) have been obtained by adding 2 equivalents of alkali metal to the dithioacetals (CH2)nC(SR)2. The cleavage reactions mentioned proceed with good to almost quantitative yields. The conversion of cycloalkyl ethyl sulfides and cycloalkanone diethyl dithioacetals with alkali metals is suitable for the preparation of the three‐ and six‐membered ring thiols but proceeds unsatisfactorily in the case of the five‐ and seven‐membered rings, cleavage between the ring and sulfur being the main reaction.