Studies on the reactivity of methyl γ-tosylcrotonoate as ambident reagent in organic synthesis

The treatment of methyl(E)-4-tosyl-2-butenoate (4) with two equiv. of sodium hydride and different mono and dihalides gives mainly γ,γ- and ,- or ,γ- and ,-dialkylated products (5–7) depending on the electrophile. The corresponding monoanion dimerizes with iodine to afford stereoselectively dimethyl cis-4,5-ditosyl-2,6-cyclohexadiene-1,2-dicarboxylate (11). The tosyl group in compounds 6 and 7 is reduced and in the case of γ,γ-dimethylated 5a substituted by sodium dimethyl malonate under Pd(PPh₃)₄ catalysis. Michael addition of different nucleophiles provides the corresponding β-substituted methyl γ-tosylbutanoates 16.