Synthesis and Structure of 3,4‐Dihydropyrido[2′,3′:3,4]pyrazolo[1,5‐ a ][1,3,5]triazin‐2‐amines [1][Dolzhenko, A. V., 2011]

A new convenient synthon for heterocyclic chemistry, namely 1 H ‐pyrazolo[3,4‐ b ]pyridin‐3‐ylguanidine was successfully prepared by selective guanylation of 1 H ‐pyrazolo[3,4‐ b ]pyridin‐3‐amine. A series of 3,4‐dihydropyrido[2′,3′:3,4]pyrazolo[1,5‐ a ][1,3,5]triazin‐2‐amines was synthesized from 1 H ‐pyrazolo[3,4‐ b ]pyridin‐3‐ylguanidine using aldehydes or ketones as one‐carbon inserting reagents. The tautomeric preferences of the products were determined using spectroscopic ( e.g ., 2D NOESY NMR) and single crystal X‐ray diffraction data.