Developments towards synthesis of N-heterocycles from amidines via C-N/C-C bond formation

The synthesis of N-heterocycles is one of the most active areas due to their structures with extensive applications in the fields of organic, pharmaceutical and materials chemistry. It is an increasingly challenging task to develop greener, milder and cheaper N-heterocycle synthetic strategies through C-N/C-C bond formation owing to the requirement of multistep reactions or harsh reaction conditions in many cases. Herein, this review focuses on the synthesis of N-containing heterocycles such as pyrimidines, imidazoles, 1,2,4-triazoles, 1,3,5-triazines, benzimidazoles, isoquinolines, quinazolines, quinazolinones, 1,2,4-oxadiazoles, thiazoles, and thiadiazoles using amidines as readily available starting materials, with an emphasis on the novel green synthetic methodologies via C-N/C-C bond formation, as well as the mechanisms of these reactions. We hope that this review will help as a reference for researchers who are fascinated with the increasing applications in this prolific area.