The synthesis of pyridine derivatives from 3‐formylchromone

Abstract

3-Formylchromone(1) reacts with active methylene derivatives to yield condensation products 2a-d, 1 0 , l l and 12. Treatment of 2a-d with ammonia or methylamine gives pyridines 3-6. Alternatively, reaction of 1 with enamine derivatives yields pyrido compounds 15, 17, 19, 21, 23 and 28 in one step. Factors determining the formation and regiospecificity of the pyridine ring forming reactions are also discussed.1.

3-Formylchromones as diverse building blocks in heterocycles synthesis

“…When the reaction took place in aqueous ethanol containing pyridine or aqueous pyridine by molar ratio (1:2) afforded the adduct 132 which dehydrated to formxanthone 133 in 73% yield (Scheme 63) [60,76,90].…”

“…Treatment of 3-formylchromone (1a) with barbituric acid 137a, thiobarbituric acids 137b and 1,3-dimethylbarbituric acid 138 gave 5-[(4-oxo-4H-chromen-3-yl)methylene] pyrimidine derivatives 139 and 140,respectively (Scheme 66) [76,77].…”

“…Chromenopyridines 168 were prepared by treating 3-formylchromone 1a with enaminonitriles, enaminoketones or β-aminoesters 167 (Scheme 82) [63,64,76,120].…”

“…Interaction of 3-formylchromones 1a-c,g with ethyl glycinate in boiling toluene in the presence of p-toluenesulfonic acid gave a mixture of ethyl 4-(2-hydroxybenzoyl)-6-(4-oxochromen-3-yl)-pyridine-2-carboxylates 169 and ethyl 4-(2-hydroxybenzoyl)pyrrole-2-carboxylates 170 (Scheme 83) [62,65,76,121].…”

“…Reaction of 3-formylchromone 1a with enamine derivatives 185-189 in pyridine or glacial acetic acid led to fused pyridine derivatives 190-194 in one step, respectively (46-82% yields) (Scheme 90) [76].…”