Síntese verde de 3-fenilquinoxalin-2(1H)-onas através da ciclocondensação entre α-cetoácidos e o-fenilenodiaminas

Abstract

In the present work, the synthesis of 3-phenylquinoxalin-2(1H)-ones 3 is described through a method that meets the principles of green chemistry. For this, α arylglyoxylic acid (PGA) 1 and o-phenylenediamine 2 were used as starting materials. The reactions were performed under niobium ammonium oxalate (ANO) catalysis using low density polyethylene glycol (PEG-400) as solvent and under ultrasound irradiation (US). From the developed method were prepared twenty one molecules belonging the class of 3-phenylquinoxalin-2(1H)-ones 3 in yields from 34 to 96%. Among the synthesized compounds, it is important to highlight that twelve molecules are unpublished. Another important factor is related to the presence of donor or electron withdrawing groups in the starting materials, which directly affected the reactivity and selectivity of the obtained products. In this context, the presence of a nitro group, a strongly electron-withdrawing group, in the aromatic ring portion of o phenylenediamine 2 decreased the yields, in which case a mixture of by-products was observed.