Método sencillo para la obtención de ácidos 2-fenoxibenzoicos asistido por ultrasonido en dimetilformamida como disolvente

Abstract

The classical arylation procedure of phenols with aryl halides under Ullmann condensation conditions for
the synthesis of 2-phenoxybenzoic acids using copper powder or copper salts requires harsh reaction conditions as a
result of the poor nucleophilicity of phenoxide and the low reactivity of the aryl halide involved. In the present work a
new modification to the condensation of 2-chlorobenzoic acids and phenols using ultrasound as a energy source, potassium
carbonate as base, copper powder as catalyst, pyridine as ligand and N,N-dimethylformamide as solvent was performed.
This permits to develop an operationally simple one pot method via Ullmann condensation of 2-chlorobenzoic
acids and phenols to give 2-phenoxibenzoic acids. The authors modify different reaction conditions changing the quantities
of base, ligand and reaction time. The optimum conditions were: 2-chlorobenzoic acid-phenol-potassium carbonate-
pyridine, as 1 : 2 : 1.5 : 0.75 mol in presence of Cu 3 % (w/w) related to 2-chlorobeizoic acid. The reaction time was
10 min. In order to generalize this procedure several 2-phenoxibenzoic acid derivatives were prepared obtaining 87 - 96 %
yield which are superior to those obtained using classical heating conditions, where is necessary 2.5 h . reaction time.
The products obtained were identified using a combination of analytical spectroscopic techniques