Versatile Three-Component Procedure for Combinatorial Synthesis of 2-Aminospiro[(3′H)-indol-3′,4-(4H)-pyrans]

A convenient method of synthesis of substituted and annulated 2-amino-spiro[(3' H)-indol-3',4-(4 H)-pyrans] at mild conditions and in good yields is developed. Three component reaction of wide variety of substituted isatins, cyanoacetic acid derivatives, and carbonyl compounds or phenols gives the target compounds. Forty new spiropyrans were obtained, and their structures were proved by elemental analysis and 1H NMR and IR spectral data. It is shown that the use of a not very large set of starting compounds can lead to the synthesis of a thousand-member 2-amino-spiro[(3' H)-indol-3',4-(4 H)-pyran] library.