Indole Substrates to Carbazole Targets: An Update in the Discovery of an Ideal Synthetic Methodology

Carbazole compounds have been proven to exhibit vital photophysical and biological applications. Even simple carbazole derivatives were showing attractive biological activities such as antimicrobacterial activity (Glycozoline), antiproliferative activity (Mukonine), free radical scavenger (Carazostatin), etc. In case of photophysical applications, carbazole derivatives were utilized in organic semiconductors, photoconducting polymers, Green host material in phosphorescent organic light-emitting diodes (OLEDs), hole-transporting material in OLEDs and organic light emitting materials. An account of different synthetic methodologies involved in the synthesis of natural and synthetic carbazole derivatives was evaluated based on the usage of commercially available cheap starting materials such as derivatives of Indole. This paper takes into account the time from 2011 to 2023. The advanced methods were developed based on the 12 principles of Green chemistry such as Multistep domino reactions, Atom & Step economy reactions, protection-free reactions, mild reaction conditions, open atmosphere reactions, harmless by-products and photochemical transformations.