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Ring closure reactions of pyrido[2,3-d]pyrimidines to pyrano[2′,3′:4,5]- and oxazolo[5′,4′:4,5]pyrido[2,3-d]pyrimidines

✍ Scribed by Dang Van Tinh; Wolfgang Stadlbauer

Publisher: Journal of Heterocyclic Chemistry
Year: 2008
Tongue: English
Weight: 419 KB
Volume: 45
Category: Article
ISSN: 0022-152X
DOI: 10.1002/jhet.5570450517

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✦ Synopsis

Abstract

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The cyclocondensation of 5‐hydroxy‐pyrido[2,3‐d]pyrimidines 1 with malonates gives pyrano[2′,3′:4,5]‐pyrido[2,3‐d]pyrimidines 2. Nitration of 1 and reduction with zinc in the presence of carboxylic acids/anhydrides gave 2‐alkyloxazolo[5′,4′:4,5]pyrido[2,3‐d]pyrimidines 4, which were ring‐opened to 6‐aminopyrido[2,3‐d]pyrimidines 5, 6 and 7. Cyclization of 6‐aminopyrido[2,3‐d]pyrimidines 6 with benzoylchlorides 8 gave 2‐aryloxazolo[5′,4′:4,5]pyrido[2,3‐d]pyrimidines 9. Reaction conditions for the cyclization have been studied by differential scanning calorimetry (DSC).

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