One-Pot Synthesis of Functionalized Carbazoles and -Carbolines via Diethyl Azodicarboxylate Mediated Dehydrogenative Aromatization in Deep Eutectic Solvent

Herein we report a one-pot approach for the functionalized carbazoles and beta-carbolines via Fischer indole/Pictet-Spengler type reactions followed by diethyl azodicarboxylate (DEAD) mediated dehydrogenative aromatization using Deep Eutectic Solvent (N,N'-Dimethyl urea and L-tartaric acid combination) as reaction medium. This one-pot method enables the synthesis of library of compounds of carbazoles and beta-carbolines with good to excellent yields in short reaction times. The developed method was extended for the copper-mediated reaction to minimize the amounts of DEAD required. Also, the application of gram scale reaction and reusability of the DES (in both cases) is demonstrated efficiently.