Cyclocondensation of coumarin-3-thioformates with 3-hydroxyoxindoles and 3-aminooxindoles for the synthesis of spiro-fused pentaheterocyclic compounds

Abstract

Coumarin-3-thioformates acting as a new type of 3-carbon partner were firstly prepared and engaged in reacting with 3-hydroxyoxindoles and 3-aminooxindoles by using DABCO or Et₃N as the catalyst. A wide scope of structurally diverse spiro-fused pentaheterocyclic compounds including spiro-butyrolactoneoxindole[3,4-c]coumarins and spiro-butyrolactamoxindole[3,4-c]coumarins, which combined oxindole, dihydrofuranone or pyrrolidone, and coumarin in one molecule, could be smoothly obtained in high yields via a tandem Michael addition–lactonization/lactamization process under mild conditions.