Comparative study of synthetic approaches to 1-arylmethylenepyrazino[2,1- b]quinazoline-3,6-diones

Abstract

The transformation of 3-arylmethylenepiperazine-2,5-diones ( 1) into 1-arylmethylene-2,4-dihydro-1 H-pyrazino[2,1- b]quinazoline-3,6-diones ( 2) was studied. Four synthetic methods were compared, namely direct condensation with the product of the reaction between anthranilic acid and thionyl chloride, transformation into monothioiminoethers or monoiminoethers followed by reaction with anthranilic acid derivatives, and monoacylation with o-azidobenzoyl chloride followed by intramolecular aza-Wittig reaction. The best results were obtained by the latter method.