Direct Synthesis of N-H Carbazoles via Iridium(III)-Catalyzed Intramolecular C–H Amination

Abstract

The iridium-catalyzed dehydrogenative cyclization of 2-aminobiphenyls proceeds smoothly in the presence of a copper cocatalyst under air as a terminal oxidant through intramolecular direct C-H amination to produce N-H carbazoles. A similar iridium/copper system can also catalyze the unprecedented dimerization reaction of 2-aminobiphenyl involving 2-fold C-H/N-H couplings.

Room-Temperature Direct Arylation of Anilides under External Oxidant-Free Conditions Using CO2-Derived Dimethyl Carbonate (DMC) as a ′Green′ Solvent

“…A palladium(II)‐catalyzed [5+2] oxidative annulation of 5 a with diphenylacetylene to azepine derivative ( 8 ) was successfully demonstrated. In the presence of catalytic amounts of [Cp*IrCl 2 ] 2 (2 mol %) and Cu(OAc) 2 (20 mol %), as well as PivOH (1 mmol) under air the ortho ‐aryl anilines, were selectively converted into carbazole derivatives 9 a‐b in good yields …”

Biphilic Organophosphorus-Catalyzed Intramolecular Csp2–H Amination: Evidence for a Nitrenoid in Catalytic Cadogan Cyclizations

“…Among the methods to synthesize carbazoles 1a,3 and indoles, 4 those involving direct cyclization via C–H amination are attractive. 5 The carbazole-/indole-forming method of Sundberg, involving heterocyclization by thermolysis or photolysis of o -azidonitrobiaryls and o -azidostyrenes and proceeding via an arylnitrene C–H insertion pathway, 6 exemplifies the efficiency of this bond construction (Figure 1A). Transition metal catalysts have more recently been found to bring about similar transformations of such azide substrates under milder thermal conditions, 7 although the inherent hazards associated with the preparation and handling of azide containing intermediates represent a practical constraint for such protocols on process synthesis scales.…”

An Efficient, Solvent-Free and Green One-Pot Protocol for the Rapid Access to Polyfunctionalized Carbazoles

“…Moreover, carbazole derivatives have versatile applications in material science such as organic photovoltaic devices, organic light‐emitting diodes (OLEDs), field‐effect transistors etc . Besides the great success of classical routes, there are enormous number of modern approaches available for the syntheses of substituted carbazoles which include transition‐metal‐salts (iron,– palladium,– copper,– gold,– rhodium,– iridium, etc) promoted one‐pot C–C and C–N bond‐forming reactions, C–H/N–H bond activation, and cyclization reactions by using various forms of biaryl derivatives.…”