Approaches to Carbazole Synthesis

February 29, 2024

• Title:       

  Approaches to Carbazole Synthesis

• Image Source:

  Silver-copper co-catalyzed cascade intramolecular cyclization/desulfinamide/dehydrogenation: One-pot synthesis of substituted carbazoles

• Mark:

  Scheme 1

• Associated context:

  Therefore, the development of methods for constructing  carbazole derivatives has attracted increasing attention in  recent years. Reported methods include the classical Fischer–Borsche cyclization4 (Scheme 1a) and Graebe–Ullmann5 routes,the Cadogan cyclization6 (Scheme 1b), transition-metal-catalyzed cyclization,7 and variants of indole-templated annulation reactions.8 In addition, the use of visible-light mediated cyclization for carbazole synthesis was recently reported.9A catalytic cascade approach is a potential alternative  with many advantages. Catalytic cascade reactions are  efficient, atom-economical, and environmentally friendly and  are increasingly being used for the direct construction of target  molecules.10-12 In particular, gold-or palladium-catalyzed  intermolecular cascade reactions between two alkynes have  emerged as effective tools for the synthesis of aryl-annulated[a]carbazoles (Scheme 1c). Herein, we report a  protocol for the synthesis of substituted carbazoles by means  of a silver and copper co-catalyzed tandem intramolecular cyclization/C Nbond cleavage/dehydrogenation reaction (Scheme 1d).