Investigations in the field of benzoxa- zines. 15*. Tandem heterocyclizations with the participion of 2-formylbenzoic acid. The synthesis of isoindolo[1,2-b][1, 3]- and -[2,1-a][1, 3]benzoxazinones

Abstract

Keywords: 2-(1-aminoalkyl)phenols, 2-aminophenylcarbinols, 10H-isoindolo[1,2-b][1,3]benzoxazin-12(4bH)-ones, 5H-isoindolo[2,1-a][3,1]benzoxazin-11(6aH)-ones, 2-formylbenzoic acids.Tetracyclic condensed structures containing an annelated isoindole fragment are widely distributed in nature and have a broad spectrum of biological activity that is well reflected in recent reviews [2,3]. Hence there is much interest in developing new routes for their synthesis. The isoindolo[2,1-a][3,1]benzoxazine system has been described in the literature, however, most data concerns isoindolo[2,1-a][3,1]benzoxazine-5,11-diones [4][5][6][7], while the synthesis of derivatives of 5,6a-dihydroisoindolo[2,1-a][3,1]benzoxazin-11-ones has been reported in only one publication [8] to our knowledge. The authors of this article used the 2-amino ketone phthalimides A as starting compounds, and these were converted to the respective structures B through a simple sequence of reactions.Despite the simplicity of the scheme, this method still has an important drawback, since the use of asymmetrically substituted phthalic anhydrides in the synthesis of the phthalimides A should lead to a mixture of isomeric alcohols C. To avoid this difficulty, derivatives of 2-formylbenzoic acid can be used. It is well known that 2-formylbenzoic acids can react with binucleophiles containing at least one primary amino group to give annelated isoindolinones [9][10][11][12].