The synthesis of 5-Alkylidenefuran-2(5H)-ones

5-Alkylidenefuran-2(5H)-ones can be synthesized efficiently from S- methyl 5-oxo-2,5-dihydro-furanylidenealkanethioates by treatment with Raney nickel. The ylidenealkanethioates are prepared from the Wittig reactions between cyclic anhydrides and (methylthio)carbonylmethylenetriphenyl-phosphorane or its alkylated derivative. The decarbonylation-desulfurization process proceeds largely with retention of configuration about the double bond. It is considered that the reaction proceeds by loss of carbon monoxide to give a thioenol ether which is subsequently hydrogenolysed to the 5- alkylidenefuran-2(5H)-one.