Synthesis of substituted pyrazolo[4,3-b]pyridines via copper-mediated intramolecular C–N cross-coupling of primary allylamines

Abstract

Copper-catalyzed intramolecular amination followed by in situ oxidation of primary allylamines generated from the Morita–Baylis–Hillman adducts of 4-iodopyrazolecarbaldehydes for preparing substituted pyrazolo[4,3-b]pyridines is described. The synthetic methodology is versatile and is not affected by the stereochemistry of the allylamine. In contrast, similar coupling reactions employing secondary allylamines as the starting material were unsuccessful.