Synthesis of Substituted 1,2,3,4-Tetrahydro-1-thiacarbazole and Spiro[pyrrolidinone-3,3′-indolinones] through a Common Intermediate Obtained by Condensation of Indolin-2-one, (Aryl)aldehydes, and Meldrum's Acid
Trimolecular adducts resulting from condensation between indolin-2-one (or indoline-2-thione), (aryl)aldehydes, and Meldrum’s acid are useful intermediates for the synthesis of either 1,2,3,4-tetrahydro-1-thiacarbazoles or spiro[pyrrolidino-3,3′-oxindoles] related to the natural product horsfiline. These latter compounds were obtained in a three-step procedure characterized by acyl azide formation