2-(Arylamino)aryliminophosphoranes as Easily Available and Convenient Starting Materials in the Synthesis of 1,2,3-Benzotriazoles

Abstract

1-Aryl-1,2,3-benzotriazole systems are synthesized in the high-yielding cyclocondensation of 2-(arylamino)aryliminophosphoranes under mild conditions. The reaction concludes the three-step, halogen-free synthetic route starting from simple nitroarenes and arylamines.

Synthesis of 1-arylbenzimidazoles and dibenzo[b,e][1,4]diazepines from 2 (arylamino)aryliminophosphoranes

“…Preparation and characterization of 2-(arylamino)aryliminophosphoranes 1 have been described in our previous papers. [9][10][11][12] General procedure for the reactions of iminophosphoranes 1 with acyl chlorides: To a solution of iminophosphorane 1 (1 mmol) and benzoyl chloride 2 (1.1 mmol) in CH 3 CN (10 mL) was added NEt 3 (2 mmol). The mixture was stirred at reflux temperature for the time specified in Table 1.…”

“…[3][4][5][6][7][8] An attractive transformation of 2-nitrosodiarylamines appeared to be their smooth reaction with triphenylphosphine, first published in 2014, 9 leading to 2-(arylamino)aryliminophosphoranes via a Cadogan-type reaction. These turned out to be versatile and stable equivalents for 1-aryl-1,2-arylenediamines; they reacted with isocyanates, 9 nitrous acid, 10 CS 2 11 and CO 2 12 furnishing 2-aminobenzimidazoles, benzotriazoles, 2-thiobenzimidazoles and 2-benzimidazolones respectively (Scheme 1).…”

“…From our previous work it became clear that reactions of 1 with alkyl isocyanates, CS 2 and CO 2 proceed via initial addition of the iminophosphorane nitrogen atom to the carbonyl group of the other reagent, while the reactions with nitrous acid, leading to the benzotriazole system, seems to proceed in two different ways, including one involving initial nitrosation of the arylamine nitrogen atom. 10 In this paper we present the results of reactions of 2-(arylamino)aryliminophosphoranes (1) with simple acylating agents such as acid chlorides and Vilsmeier reagents. Although both kinds of reagents are widely used for the introduction of a carbonyl function into nucleophilic centres, the Vilsmeier reaction is mainly known for the formylation of electron rich aromatic and heteroaromatic rings.…”

Quaternization of 2-(arylamino)aryliminophosphoranes. A route to N,N'-disubstituted 2-aminodiarylamines and unsymmetrically substituted 1-aryl-1,2,5,6-tetrahydro-1,6-benzodiazocines

“…Preparation and characterization of 2-(arylamino)aryliminophosphoranes 1a-c,f,g,i,j,l, 2b and 2i-k have been described in our previous papers. [1][2][3] General procedure for the synthesis of new iminophosphoranes 1. To a stirred suspension of Ph 3 P (12.5 mmol, 3280 mg) in dry MeCN (25 mL) the appropriate N-aryl-2-nitrosoaniline (5 mmol) was added portionwise during 30 min under external cooling with cold water.…”

“…In 2014 we described a practical synthesis of 2-(arylamino)aryliminophosphoranes from 2-nitrosodiarylamines, easily accessible from the reaction of nitroarenes and anilines. 1 We demonstrated their versatility as N-substituted arylenediamine equivalents in the synthesis of fused bicyclic heterocycles such as benzimidazoles, 2 2-aminobenzimidazoles, 1 benzotriazoles, 3 benzimidazol-2-ones, 4 benzodiazepines, 2 and benzimidazole-2-thiones. 5 Their ylide-like structure, a consequence of the charge distribution within the iminophosphorane group, determines the nucleophilic character of the nitrogen atom, which is susceptible to reaction with electrophiles.…”