RING-TRANSFORMATIONS OF PYRIMIDINES BY INTRAMOLECULAR DIELS-ALDER REACTIONS. SYNTHESIS OF ANNELATED PYRIDINES

Article abstract of DOI:10.1016/0040-4020(89)80111-5

Pyrimidines carrying an ω-alkyne side-chain -XCH2CH2CCH (X=O,N,S,SO,SO2) at the 2 or 5 position undergo intramolecular inverse electron demand Diels-Alder reactions across the C-2 and C-5 positions; elimination of hydrogen (or alkyl) cyanide from the intermediate adducts leads to condensed pyridines.The influence of the hetero atom (X) in the dienophilic side-chain and that of substituents in the pyrimidine ring on the reactivity is discussed.