Alkylthiomethylene groups

Just as the blocking of active sites to permit alkylations on less reactive sites has been a recurring problem, so has the problem of preventing polyalkylations on reactive sites. The use of the alkylthiomethylene group offers a convenient intermediate from which monomethylated products are prepared by desulphurization with Raney nickel. In this way, 2,3,5,5-tetramethylcyclohexanone was prepared in 58% overall yield from... 

Of course, the use of the alkylthiomethylene group first for blocking and later as a route to monomethylation further expands its utility. Thus, compound 103 was methylated and desulphurized to give the trimethyl derivative 106 . 

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