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Part-IISynthesis of PyrimidinesENuNOne pot concerted mechanismRType A(carbonyl)E+Nu(amino)NRType BENuNRNuElectrophilic attack on "N" of the nitrile,followed by intramolecular nucleophilic attack.ENRENuNRType CENHENNuRNuRNucleophilic attack on "C" of the nitrile,followed by intramolecular nuleophilic attack.Scheme 3Of the above three mechanisms the type C mechanism is the most favored mechanismand is mostly reported.1.4 Synthesis of Various Condensed Pyrimidines under the Influence of Dry HCl GasThis enhanced reactivity of nitriles in the presence of acids has been particularlyexploited for the synthesis of condensed pyrimidines. A host of nitriles have been reactedwith various o-aminocarbonyl compounds to obtain a variety of condensed pyrimidines.This approach has led to the development of a facile, one pot synthesis of condensed 2-substituted functionalised pyrimidines of wide applicability 23-30 . A variety of o-aminocarbonyl compounds, such as o-aminoesters 9, o-aminoamides 10, o-aminoketones11 and o-aminonitriles 12 have been reacted with nitriles to obtain the correspondingcondensed 4-oxo I, 4-aryl II, and 4-aminopyrimidines III.OOY+ RCNNHNH 29, Y = OR 110a, Y = NHR 1R 1 = H, alkyl, aryl, etc.NIR225