An Unprecedented Synthesis of N‐Phenyl Amides via Cleavage of Benzotriazole Ring under Free Radical Condition

Abstract

An attempt of Bu3SnH mediated cyclization of acylbenzotriazoles (RCOBt) to corresponding benzoxazole failed; instead, corresponding N‐phenylamides were achieved in good yield. The reactions proceed via reductive cleavage of benzotriazole ring with consequent evolution of molecular nitrogen (N2). A diverse range of amide has been achieved in high yields. Structures of all the compounds have been elucidated using IR, MS, 1H and 13C NMR, while four of them (3 o, 3 w, 4 and 5) have also been characterized by single crystal X‐ray analysis.

A new methodology for the synthesis of N-acylbenzotriazoles

“…1H-1,2,3-Benzotriazol-1-yl)(3-(trifluoromethyl) phenyl)methanone (2f). 27 White (1H-1,2,3-Benzotriazol-1-yl)(3-methoxyphenyl)methanone (2g). 1-(1H-1,2,3-Benzotriazol-1-yl)-2-phenylethanone (2h).…”

“…[1][2][3][4][5][6][7][8][9] N-acylbenzotriazoles are one of the most useful benzotriazolederivatives which have been successfully utilized to prepare numerous biologically relevant compounds under neutral and mild conditions by N-, C-, S-, and O-acylations. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] In recent years our group has been involved in exploration of the synthetic utility of N-acylbenzotriazoles to make sugar amides by N-acylation, 25 benzoxazoles and N-phenylamides by benzotriazole ring cleavage 26,27 and ureas, carbamates and thiocarbamates by the Curtius rearrangement. 28 The earlier synthetic methods for conversion of carboxylic acids to N-acyl benzotriazole i.e.…”

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.…”

“…[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]…”

“…Tiwari's group has performed significant research in this field. [14][15][16][17][18][19][20][21] In 2013, we developed a novel protocol for the synthesis of various benzothiazole glycoconjugates from protected carbohydrates through intramolecular cyclization (Scheme 35). 14 This reaction underwent free radical scission of the N-N bond of the benzotriazole ring by treatment with a stannane under heating or microwave irradiation.…”