Novel synthetic protocol toward pyrazolo[3,4‐h]‐[1,6]naphthyridines via Friedlander condensation of new 4‐aminopyrazolo[3,4‐b]pyridine‐5‐carbaldehyde with reactive α‐methylene ketones

Abstract

AbstractNovel pyrazolo[3,4‐h][1,6]naphthyridine derivatives 6, 8, 9, 11, 13, and 15 have been synthesized by Friedlander condensation of new 4‐amino‐3‐methyl‐1‐phenyl‐1H‐pyrazolo[3,4‐b]pyridine‐5‐carbaldehyde (o‐aminoaldehyde) 4 with active methylene ketones, such as symmetric acetone 5a, monoalkylketones 5b, 5c, 5d, 5e, 5f, 5g, 5h, 5i, 5j, 5k, unsymmetrical dialkyl ketones 7a, 7b, p‐bromophenylacetonitrile 10, β‐ketoester 12a, β‐ketoamide 12b, or diethyl malonate 14, respectively. J. Heterocyclic Chem., (2011).