Versatile three-component procedure for combinatorial synthesis of spiro-oxindoles with fused chromenes catalysed by L-proline

An efficient synthesis of spiro-oxindoles is accomplished by a one-pot three-component condensation of isatin, malononitrile or cyanoacetic ester and naphthol in the presence of L-proline as a catalyst. This method is of great value because of its shorter reaction times, high yield, and easy processing.