HPTLC FOR MONITORING THE KINETICS OF FORMATION OF QUINOXALINE DERIVATIVES .2. BENZOQUINOXALINONE DERIVATIVES

The synthesis of quinoxaline derivatives by the Hinsberg reaction foll owed by use of HPTLC to separate the resulting positional isomers and monitor the kinetics of the reaction was reported in this journal in 1 990. In this investigation, benzoquinoxalinone derivatives were synthe sized by the same method but occasionally a different problem arose. A lthough reaction does not produce positional isomers, the UV absorptio n spectra of one the starting compounds (2,3-diaminonaphthalene) overl apped with that of the final product (a benzoquinoxalinone derivative ) at every wavelength, with the result that the classic UV method coul d not be used to follow the kinetics of the reaction.The use of HPTLC enabled the calculation of rate constants for the synthesis of some be nzoquinoxalinones, enabling the discovery of differences between this reaction and that previously reported, and the postulation of a possib le mechanism for the annulation reaction.