Recent advances in the synthesis of indole embedded heterocycles with 3-diazoindolin-2-imines

Indole embedded α-diazo amidines (i.e. 3-diazoindolin-2-imines) are important additions to the cyclic diazo compound family. The ease of their preparation, typical reactivity as diazo compounds, successful generation of Rh, Cu, Pd, Co and Au carbenes in situ and their numerous transformations make them an imperative part for modern synthesis of indole embedded heterocycles. Chemistry and synthetic applications of these valuable cyclic diazo compounds are reviewed here.