Synthesis of 3-(γ,δ-Disubstituted)allylidene-2-Oxindoles from Isatins by Wittig Reaction with Morita-Baylis-Hillman Bromides

Various 3-(γ,δ-disubstituted)allylidene-2-oxindoles were synthesized by the Wittig reaction between isatins and the phosphorous ylide derived in situ from the Morita–Baylis–Hillman bromides. The 3-allylidene-2-oxindole could be used as an efficient synthetic precursor of 1-thiacarbazole derivatives. During the conversion of 2-oxindole moiety to 2-thiooxindole by Lawesson's reagent, 1-thiacarbazole derivative was obtained in good yield.