Highly Efficient Ligands for the Palladium‐Assisted Double N‐Arylation of Primary Amines for One‐Sep Construction of Carbazoles

Abstract

A highly efficient one-pot synthesis of carbazoles via palladium-catalyzed double N-arylation of primary amines with 2,2'-dihalobiphenyls is described using a catalyst system comprised of tris- (0) (Pd 2 dba 3 ) and the proazaphosphatrane P(i-BuNCH 2 CH 2 ) 3 N (8) or its derivative (t-Bu) 2 P=N À P(iBuNCH 2 CH 2 ) 3 N (9a) as the ligand. The process is effective for double N-arylation of 2,2'-biphenyl dibromide, diiodide, and even dichloride with a variety of primary amines including neutral, electronrich, electron-deficient, and sterically hindered anilines as well as aliphatic amines.

Photoinduced Ullmann C–N Coupling: Demonstrating the Viability of a Radical Pathway

“…This residue was purified by column chromatography on silica gel, eluting with hexanes, affording N-(1-naphthyl)carbazole as a white solid. The NMR parameters for the isolated material match those previously reported (45 At the end of the reaction time the reaction mixture was a clear, pale pinkish-orange. The reaction mixture was then opened to air, diluted with diethyl ether (15 mL), and washed with distilled water (3 x 5 mL).…”

A Tuned Bicyclic Proazaphosphatrane for Catalytically Enhanced N‐Arylation Reactions with Aryl Chlorides

“…Additional observations of note are that our palladium loading (0.25 mol-%) is one-half that previously reported for Pd 2 (dba) 3 -catalyzed carbazole synthesis, and the reaction temperature is lower. [17] Furthermore, unreactive primary amines, including electron-poor 3u and aliphatic 3v and 3w, gave rise to unexpectedly higher yields of Table 5. Pd/1e-catalyzed N-substituted carbazole synthesis from various primary amines and 2,2Ј-dichlorobiphenyl.…”

“…[a,b] [a] Reaction conditions: 2,2Ј-dichlorobiphenyl (0.5 mmol), aniline (0.6 mmol), Pd 2 (dba) 3 N-substituted carbazoles than we obtained previously under mild conditions. [17] …”

Palladium-catalyzed synthesis of N-arylated carbazoles using anilines and cyclic diaryliodonium salts

“…The majority are transition-metal mediated. Starting from functionalized 2,2 ' -biphenyls (path A) [10–13] or the direct arylation [14–15] of the free NH-functionality of carbazole (path B).…”