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Communication | Regular issue | Vol 20, No. 4, 1983, pp.597-600
Published online, 1st January, 1970
DOI: 10.3987/R-1983-04-0597
Studies on Ketene and Its Derivatives 114. 1,4-Cycloaddition of Ketene to Ethyl N-(2-Pyridyl)formimidates

Nobuya Katagiri, Ryuji Niwa, and Tetsuzo Kato

*Pharmaceutical Institute, Tohoku University, Aobayama, Sendai 980-8578, Japan


Reaction of ketene with ethyl N-(2-pyridyl)formimidate (1a) in acetone at room temperature gave 3-acetylpyrido[1,2-a]pyrimidin-4(4H)-one (2) whereas excess ketene gas was passed over the imidate 1a without solvent at 75 °C to give pyrido[1,2-a]pyrimidin-4(4H)-one (3a) and 2-formamidopyridine (4a), both of which would be formed by 1,4-cycloaddition of ketene. Similarly, reactions of ketene with the methyl analogs 1b-e were also carried out to give pyridopyrimidines (3b-e) and 2-formamidopyridines (4b,c,e).