Recent developments in the chemistry of bicyclic 6-6 systems: Chemistry of pyrido[1,2-c]pyrimidines

The present review provides a study on the structural features, reactions, and synthetic methodologies of pyrido[1,2-c]pyrimidines. The maximum deviation from the mean plane of the pyridopyrimidine skeleton of 4-(pyridin-2-yl)-1H-pyrido[1,2-c]pyrimidine-1,3(2H)-dione indicated a reasonably planar system. The aim of this review is to give an overview of the diverse methodologies that have been reported on the chemistry of pyrido[1,2-c]pyrimidines. The different synthetic routes have been grouped according to the way the pyrido[1,2-c]pyrimidine moiety has been created. Thus, pyrido[1,2-c]pyrimidine compounds were obtained by the formation of one bond α to the bridgehead nitrogen atom [6+0(β)] and formation of two bonds from ([3+3], [4+2], and [5+1]) atom fragments. The mechanistic pathways of the reactions are discussed.