An efficient substituent dependent synthesis of congested pyridines and pyrimidines

An efficient and versatile synthesis of various congested pyridines 3a–h, 6a,b, 8a–n, 10a–g, and 16a,b, and (pyrimidin-4-yl)acetonitriles 13a–g has been delineated by base catalyzed ring transformation of suitably functionalized 2H-pyran-2-ones 1a–h, 5, 7, and 15 by formamidine acetate 2a, acetamidine hydrochloride 2b, S-methylisothiourea 9a, pyrazol-1-yl-carboxamidine 9b, and arylamidine hydrochloride 12 separately in the presence of powdered KOH in dry DMF.