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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
Author(s) -
Van Tinh Dang,
Stadlbauer Wolfgang
Publication year - 2008
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570450517
Subject(s) - chemistry , ring (chemistry) , nitration , medicinal chemistry , pyrimidine , closure (psychology) , stereochemistry , organic chemistry , economics , market economy
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).