Catalyst-free synthesis of alkyl 4-oxo-4H-pyrido[1,2-a]pyrimidine-2-carboxylate derivatives on water

An environmentally friendly and effective method to construct 4H-pyrido[1,2-a]pyrimidin-4-one, which are ubiquitous structural units in a number of biologically active compounds has been developed. In this process, the reaction using water as the solvent in absence of catalyst under the mild conditions makes transformations very green, practical, and attractive.