Novel Synthetic Routes to Thienocarbazoles via Palladium‐ or Copper‐Catalyzed Amination or Amidation of Aryl Halides and Intramolecular Cyclization.

Abstract

Abstract-Palladium or copper catalyzed aminations or amidations were performed to obtain diarylamines and diarylacetamides precursors of thienocarbazoles. The fact that an ortho-bromodiarylamine did not cyclize to the corresponding thienocarbazole under conditions known for carbazoles from ortho-halodiphenylamines, conducted us to a highly efficient method of palladium-catalyzed intramolecular cyclization with N-deprotection of ortho-halodiarylacetamides to thienocarbazoles. Other method of intramolecular cyclization of diarylamines based on the reoxidation of the Pd(0) formed by Cu(OAc) 2 , avoiding the use of stoichiometric amounts of Pd(OAc) 2 , gave thienocarbazoles in a moderate yield, including a ring A methoxylated compound. An attempt to combine palladium and copper catalyses in a 'one pot' reaction of amination and intramolecular cyclization gave as major product a N-benzo [b]thiophene substituted carbazole and the required thienocarbazole in low yield. q