2-Oxo-Driven N₂ Elimination Induced Decarbonylative Cyclization Reaction in Benzotriazoles to 6-Aminophenanthridines

Abstract

An efficient functional group induced strategy for the synthesis of 6-aminophenanthridines (6AP) has been developed as a result of an in situ generated novel system "CO-CH(N1N2)". This reaction presents a new mode of N2 extrusion in benzotriazoles that later result in decarbonylative cyclization to 6AP. This method offers an easier protocol for the synthesis of 6AP from readily available inexpensive substrates.

A Benzoquinone Imine Assisted Ring‐Opening/Ring‐Closing Strategy of the RCOCHN1N2 System: Dinitrogen Extrusion Reaction to Benzimidazoles

“…Both of these experiments indicate that copper, besides acting as a Lewis acid, increases the nucleophilicity of the BTZ through the assistance of air, which ultimately enhances the overall yield of the reaction. On the basis of our understanding of activation through the RCOCHN 1 N 2 system, [16][17][18] literature reports on the activation of copper, [19] and the above-mentioned results, we propose a mechanism for this reaction (Figure 3). The preliminary step involves the reaction of 2-oxo aldehyde 1 with 4-azidophenol (2) [20] to give product 4.…”

“…Recently, our group established a novel route for the synthesis of 6‐aminophenanthridines through a 2‐oxo driven N 2 elimination induced decarbonylative cyclization strategy. This reaction presented a creative way to extrude N 2 from benzotriazoles . Later, the same concept involving the RCOCHN 1 N 2 system was extended to the synthesis of 2‐oxoacetamidines .…”

“…This reaction presented a creative way to extrude N 2 from benzotriazoles. [16] Later, the same concept involving the RCOCHN 1 N 2 system was extended to the synthesis of 2-oxoacetamidines. [17] In continuation, we recently established the divergent behavior of 2-oxo aldehydes (OAs) towards amino acid alkyl ester hydrochlorides.…”

Recent Developments on Denitrogenative Functionalization of Benzotriazoles

“…30 In recent years, benzotriazole derivatives have been employed in inter-and intramolecular cyclizations via a denitrogenative process for the synthesis of various nitrogencontaining fused heterocycles. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] In 2009, Nakamura and co-workers reported a novel route for the palladium-catalyzed denitrogenative [3+2]cycloaddition of N-aroylbenzotriazoles 1 with internal alkynes 2 for the construction of biologically relevant indole derivatives 3 (Scheme 4). 6 Notable advantages of this novel protocol include a simple, solvent-and base-free experimental procedure, mild reaction conditions, easy separation of the product, the release of molecular nitrogen gas as the sole by-product and satisfactory reaction yields.…”

“…For instance, the transition-metal-catalyzed intermolecular cyclizations of benzotriazoles have been achieved through unsaturated hydrocarbons as coupling partners, such as internal and terminal alkynes, 1,3-dienes, allenes, N-allenamides, etc. [6][7][8][9][10][11][12][13] On the other hand, intramolecular cyclizations for the synthesis of benzothiazoles and benzoxazoles have been recently reported by the Tiwari group. [14][15][16][17][18][19][20][21]…”