I2-promoted formal [3 + 1 + 1 + 1] cyclization to construct 5-cyano-1H-pyrazolo[3,4-b]pyridine using malononitrile as a C1 synthon

Abstract

A novel [3 + 1 + 1 + 1] cyclization reaction for the synthesis of compounds based on a 5-cyano-1H-pyrazolo[3,4-b]pyridine skeleton from aryl methyl ketones, malononitrile and 5-aminopyrazoles has been established. This I₂-meditated process allows direct cleavage of the C–C bond of malononitrile to generate a C1 synthon and the construction of three C–C bonds and one C–N bond in a one-pot system. This method is facile and compatible with a wide range of substrates. Significantly, some products exhibit good aggregation-induced emission (AIE) characteristics without any further modification.