Highly stereoselective [3+2]-cycloaddition reaction of stabilised N,N′-cyclic azomethine imines with 3-nitro-2-phenyl-2H-chromenes: Synthesis of tetrahydrochromeno[4,3-c]pyrazolo[1,2-a]pyrazol-11-ones

Abstract

The reactions of 3-nitro-2-phenyl-2H-chromenes with 2-arylmethylidene-5-oxopyrazolidin-2-ium-1-ides proceeded diastereoselectively to afford the corresponding tetrahydrochromeno[4,3-c]pyrazolo[1,2-a]pyrazol-11-ones in good yields as a result of the 1,3-dipolar cycloaddition reaction of stabilised N,N′-cyclic azomethine imines at the Δ3-bond of the chromene system.