Abstract

Pyrimidines and pyrans are the special class of heterocyclic compounds with a broad spectrum of biological activities such as anticancer,
antiviral, antibacterial, antioxidant, antiallergic and antidepressant. The use of pyran derivatives is not only limitted in cosmetics, pigments
and biodegradable agrochemicals but also constitute a structural unit of many natural products. Therefore researchers have synthesized
these condensed heterocycles through different complex pathways as target structures for biological studies. This review focuses on the
various strategies followed for the convenient synthesis of pyrimidine and pyran based heterocyclic compounds. The steps included
condensation followed by cyclization or MCR, either in a step-wise manner or in one pot has been achieved successfully to obtain these
two classes of heterocycles under different conditions. Diethyl oxalate, diethyl malonate, malononitrile and ethyl cyanoacetate are the most
common reagents used for the synthesis of pyrimidines and pyrans appended on different heterocyclic skeletons.

Key words: heterocycles, pyrimidines, pyrans, diethyl malonate, malononitrile.