Copper(I)‐Catalyzed Synthesis of 4,5‐Dihydropyrazolo[1,5‐<i>a</i>]pyrimidines <i>via</i> Cascade Transformation of <i>N</i>‐Propargylic Sulfonylhydrazones with Sulfonyl Azides

Abstract

Abstract A rapid and effective approach to 4‐tosyl‐4,5‐dihydropyrazolo[1,5‐ a ]pyrimidines via copper‐catalyzed one‐pot cascade transformation of N ‐propargylic sulfonylhydrazones with sulfonyl azides under mild conditions has been developed. This process relies on the copper‐catalyzed azide‐alkyne cycloaddition (CuAAC) and intramolecular [4+2] cycloaddition of α,β‐unsaturated hydrazone with the in situ generated ketenimine intermediate, affording the useful bicyclization products with high efficiency. magnified image