COMPARATIVE-STUDY OF SYNTHETIC APPROACHES TO ARYLMETHYLENEPYRAZINO[2,1-B]QUINAZOLINE-3,6-DIONES

The transformation of 3-arylmethylenepiperazine-2,5-diones (1) into 4- dihydro-1H-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 b y 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. (C) 1998 Elsevie r Science Ltd. All rights reserved.