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

Abstract

2-(Arylamino)aryliminophosphoranes, easily obtained from 2-nitrosodiarylamines,were found to be convenient starting materials for simple reactions with common acylating reagents such as acid chlorides and the Vilsmeier reagent. The reactions allow for the synthesis of 1,2-disubstituted benzimidazoles or dibenzo [b,e][1,4]diazepines, depending on the substituents on the 2-arylamine nitrogen atom.

Proton transfer in the benzimidazolone and benzimidazolthione tautomerism process catalyzed by polar protic solvents

“…The uncatalyzed reaction may even be undetectable because the real reaction is catalyzed by KOH, 62 NaOH, 63 ice/CO 2 , 64 and t BuOH. 65…”

(2-Aminoaryl)iminophosphoranes as Versatile Starting Materials for the Synthesis of 1-Aryl-2-trifluoromethylbenzimidazoles

“…2b These compounds turned out to be versatile starting materials in the synthesis of a variety of nitrogen heterocycles like benzimidazoles, 2a 3 triazoles, 4 benzimidazol-2-ones, 5a benzimidazol-2-thiones, 5b and benzazepines. 3…”

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.…”

“…If needed, the diarylamine nitrogen atom was alkylated first, using NaH/DMF or n-BuLi/THF systems as has been described earlier. 2 Particular attention was paid to the introduction of allyl substituents on both nitrogen atoms since the resulting structures provide an opportunity for cyclization reactions.…”