Molecular Orbital Calculations for Azaquinonoid-Ketene and Analysis of the Intramolecular Cycloaddition with the N, N-Dimethylanilino Group

Abstract

Intramolecular cycloaddition of azaquinonoid-ketene (4) generated from benzotriazinone derivative to N, N-dimethylanilino group afforded "unrearranged" acridone in sharp contrast to a carbon analog series (1). Molecular orbital calculations and conformational studies using a model compound did not show much difference between azaquinonoid-ketene (11) and quinonoid-ketene (12), indicating similar propensity toward the [_π4_a+_π2_a] pathway of 4 in terms of FMO theory. These results led us to suggest the involvement of a concealed process in the transformation of 4 to "unrearranged" acridone (9), i. e., a [_π4_a+_π2_a] cycloaddition at the initial stage, by analogy with the carbon analog (1).