Microwave-Assisted, Solvent-Free Synthesis of 3′-(Aryl/Heteroaryl)-1-morpholinomethyl/piperidinomethylspiro[3H-indole-3,2′-thiazolidine]-2,4′(1H)-diones via 3-Isatinimines

The solvent-free, microwave (MW)-assisted synthesis of a new series of 3'-(aryl/heteroaryl)-1-morpholinomethyl/piperidinomethylspiro[3H-indole-3,2'-thiazolidine]-2,4'(1H)-diones has been achieved in an open vessel. Isatins 1 undergo an easy condensation with various aryl/heteroaryl at-nines by MW using montmorillonite K10 clay as a solid support to afford Schiff bases 2, which subsequently undergo smooth cyclization with TGA under neat MW conditions to afford the spiro thiazolidinones 3. The spiro-compounds are made to react with rnorpholine/piperidine and formaldehyde to give the corresponding Mannich bases 4/5 in reasonably good yield.