Crystal structure of [2]benzopyrano[3,4-b]quinoxalin-5-one through spontaneous air oxidation rearrangement of 6-Chloro-isoindolo[2,1-a]quinoxaline

Abstract

Abstract The complete structure of [2]benzopyrano[3,4- b ]quinoxalin-5-one 1 , also named isochromeno[3,4- b ]quinoxalin-5-one, was established unequivocally by a single crystal X-ray analysis. Its process of formation probably included the autoxidation of the isoindole moiety of 6-chloro-isoindolo[2,1- a ]quinoxaline 2 followed by a deshydratation and oxidation leading to a non isolated acid. Then a subsequent rearrangement of this adduct produces isochromeno[3,4- b ]quinoxalin-5-one 1 through an intramolecular cyclization. The crystal is triclinic, space group P ī with a = 7.173 (1), b = 11.668 (2), c = 13.430 (2) A, α = 85.56 (1)°, β = 83.26 (1)°, γ = 81.32 (1)°, V = 1101.4 (3) A 3 , Z = 4, C 15 H 8 N 2 O 2 , D c = 1.497 g/cm 3 , μ (MoKα) = 1.5418 A, S = 1.017, F (000) = 512.00, R = 0.0758 and wR = 0.1840. In the unit cell, there are two independent molecules.