On October 15, 2014, Yao, Qingjia; Wu, Simin; Xu, Yangjun published a patent.Electric Literature of 924909-16-0 The title of the patent was A process for preparing 4-chloro-1H-pyrazolo[3,4-b]pyridin-3-amine. And the patent contained the following:
The invention relates to a process for the preparation of 4-chloro-1H-pyrazolo[3,4-b]pyridin-3-amine via heterocyclization of 2-propenenitrile with 4-methoxybenzaldehyde followed by reaction with tri-Et orthoformate and 2,2-dimethyl-1,3-dioxane-4,6-dion, heterocyclization, chlorination, deprotection, nitration, and reduction The experimental process involved the reaction of 1-(4-Methoxybenzyl)-1H-pyrazolo[3,4-b]pyridin-4-ol(cas: 924909-16-0).Electric Literature of 924909-16-0
The Article related to chloropyrazolopyridinamine preparation mannich heterocyclization nitration, Heterocyclic Compounds (More Than One Hetero Atom): Pyrazoles and other aspects.Electric Literature of 924909-16-0
Referemce:
Pyrazole – Wikipedia,
Pyrazoles – an overview | ScienceDirect Topics