4H-Pyrido[1,2-a]pyrimidin-4-one, biologically important fused heterocyclic scaffold: Synthesis and functionalization

4H-pyrido[1,2-a]pyrimidin-4-one and their derivatives are highly bioactive and multipurpose heterocyclic motifs, having application in drugs, natural products, agrochemical, material science, and organic synthesis. The C-H functionalization of basic core structure of heterocycles have become indispensable tools that have continually increased the importance in the pharmaceutical industry for the synthesis of various useful heterocyclic molecules and their derivatives. In this review, we have provided a summary of various routes to synthesize 4H-pyrido[1,2-a]pyrimidin-4-one derivatives along with various derivatization methods such as via cross-coupling, C-H functionalization through arylation, alkenylation, sulfenylation, selenylation, phosphonation etc. taking into account the synthetic potentiality and significant influence of this scaffold in drug discovery.