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 alpha-Methylene Ketones

[摘要]：Novel 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-k, unsymmetrical dialkyl ketones 7a-b, p-bromophenylacetonitrile 10, beta-ketoester 12a, [beta-ketoamide 12b, or diethyl malonate 14, respectively.

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