Isocyanate acting as a carbonyl precursor: pyridyl group-assisted formation of 4H-pyrido[1,2-a]pyrimidin-4-ones from ketimines and isocyanates.
By the reactions of ketimines bearing a pyridyl or a picolyl group on a nitrogen atom of the imine moiety with tosylisocyanate, 4H-pyrido[1,2-a]pyrimidin-4-one derivatives could be obtained in quantitative yields. In these reactions, tosylisocyanate acts as a carbonyl precursor. The pyridyl or picolyl group is a key functional group because it is not only the constituent structure of the 4H-pyrido[1,2-a]pyrimidin-4-one framework but also the promoter of the formation of a ketene intermediate.
Kuninobu
Yoichiro
Y
Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University, Tsushima, Okayama 700-8530, Japan. kuninobu@cc.okayama-u.ac.jp
Nishimura
Shuhei
S
Takai
Kazuhiko
K