Efficient synthetic strategies for fused pyrimidine and pyridine derivatives: A review

Pyrimidine and its derivatives play a paramount role in drug discovery as privileged pharmacophores with considerable chemical and biological significance and its presence in genes. This review aims to assemble a systematic evaluation of synthetic tactics of various fused pyrimidine derivatives containing nitrogen heterocycles such as pyridopyridines, pyridopyrimidines, and pyrimidopyrimidine from a pharmacological point of view and deliver an overview of methodologies presenting the chemistry of fused pyrimidine derivatives. The review details the importance of various catalysts and ring substitution using various electrophilic and nucleophilic reagents. These synthetic strategies were elaborated based on the different synthetic routes that lead to the specific type of pyrimidine and pyridine fused derivatives. The literature accumulates various developments in one-pot condensation, the Knoevenagel–Michael addition mechanism, microwave and ultrasound irradiation, intramolecular cyclization, nano-catalytic reactions, and so forth. Short reaction times, catalyst reusability, solvent-free conditions, excellent yields, and stereo-selectivity are some of the benefits of certain synthetic approaches.