Abstract
A facile synthesis of new pyrido[1,2-a]benzimidazoles through a one-pot multicomponent reaction of malononitrile, electron-deficient aryl aldehydes and heterocyclic enamines followed by a nitrous acid release under mild condition, is reported. Depending on the substituents on heterocyclic enamine, newly synthesized products have been obtained either as an inseparable mixture of regioisomers or as a single regioisomer. A plausible mechanism can be proposed for the formation of pyrido[1,2-a]benzimidazoles via this unfamiliar transformation with the HNO2 extrusion. The structures of all title compounds were elucidated using spectroscopic methods and physical characteristics involving single crystal X-ray diffraction and TOF-MS measurements. In addition, among all the products, CN- and CF3-substituted ones showed promising absorption and fluorescent properties.
Graphical Abstract
![](/cms/asset/39b98f3b-86a2-42a3-92fd-c5cae13d5d4b/lsyc_a_1800742_uf0001_c.jpg)
Acknowledgement
Special thanks to Dr. Murat Olutas and Dr. Muhammet Yıldırım for interpreting fluorescent measurements and valuable discussions throughout this study.