Reactions with dimethylformamide‐dimethylacetal: Synthesis and reactions of several new pyridine and pyrazolo[3,4‐b]pyridine derivatives

6‐Aminopyridine‐2(1H)‐thiones 1a,b reacted with dimethylformamide‐dimethylacetal (DMF‐DMA) to give the corresponding 6‐{(N,N‐dimethylamino)methylene]amino}pyridine derivatives 2a,b . The latter compounds reacted with hydrazine hydrate to afford the 3,6‐diamino‐1H‐pyrazolo3,4‐b]pyridine derivative 4 and 3‐amino‐5‐hydrazino‐1H‐pyrazolo4′,3′:5,6]pyrido2,3‐d]pyrimidine derivative 7 , respectively. Compound 4 condensed with DMF‐DMA to yield the 3,6‐bis{(N,N‐dimethylamino)methylene]amino}‐1H‐pyrazolo3,4‐b]pyridine derivative 10 , which reacted with malononitrile to give the corresponding pyridopyrazolopyrimidine derivative 15 . © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:399–404, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20312