Heteroaromatie compounds

The Sonogashira products of halopyrimidines with pendant functional groups are good precursors for synthesizing condensed heteroaromatie compounds. Yamanaka s group prepared four different condensed heteroaromatics from further manipulations of such Sonogashira products. Those four condensed heteroaromatics are 5-oxo-7-pyrido[4,3-6/] pyrimidine 192 [94], furo[2,3-6/]pyrimidine 195 [95, 96], thieno[2,3-6/]pyrimidine 198 [95, 96], and pyrrolo[2,3-6/]pyrimidine 202 [97-100]. 

The pyridine family of heteroaromatie nitrogen compounds is reactive toward nueleophilie substitution at the C-2 and C-4 positions. The nitrogen atom serves to aetivate the ring toward nueleophilie attack by stabilizing the addition intermediate. This kind of substitution reaction is especially important in the ehemistiy of pyrimidines. 

G. Ohloff, I. Flament, The Role of Heteroaromatie Substances in the Aroma Compounds of Foodstuffs in Progress in the Chemistry of Organic Natural Products, vol. 36, Springer Verlag, Wien 1979, pp. 231-283. 

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