A Multicomponent Approach to Highly Substituted 1H‐Pyrazolo[3,4‐b]pyridines.

Multicomponent reactions make up an important subclass of azaheterocycle syntheses. In this report, a mild and catalyst-free multicomponent preparation of 1 H -pyrazolo[3,4- b ]pyridines is described. This one-pot synthesis uses simple aldehyde, 3-oxopropanenitrile, and 1 H -pyrazol-5-amine starting materials to rapidly access structurally diverse products. Additionally, the impact of 1 H -pyrazol-5-amine C3 substituents on the formation of 1 H -pyrazolo[3,4- b ]pyridines vs pyrazolo[1,5- a ]pyrimidine structural isomers is discussed.