Ethyl lactate as a promising bio based green solvent for the synthesis of spiro-oxindole derivatives via 1,3-dipolar cycloaddition reaction

Ethyl lactate as a bio based green solvent was used, for the first time to promote the 1,3-dipolar cycloaddition reaction of azomethine ylide generated in situ by the decarboxylative condensation of substituted isatin and proline with napthoquinone as dipolarophile, which generates a series of medicinally privileged spiro[benzo[f]pyrrolo[2,1-a]isoindole-5,3′-indoline]-2′,6,11-trione derivatives in excellent yields at room temperature.