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Paper | Regular issue | Vol 45, No. 3, 1997, pp.585-596
Published online, 1st January, 1970
DOI: 10.3987/COM-96-7722
■ Regiospecific Hetero Diels-Alder Synthesis of Pyrido[2,3-b]- and Pyrido[3,2-b]carbazole-5,11-diones

Ambroise Poumaroux, Zouhair Bouaziz, Monique Domard, and Houda Fillion*

*Laboratoire de Chimie Organique, Université Claude Bernard, Lyon I, 8 avenue Rockefeller, 69373 Lyon Cedex 08, France

Abstract

Diels-Alder reactions of 2- or 3-bromocarbazolequinones (8) or (9) with azadienes (1) afford regiospecifically pyrido[2,3-b]- or pyrido[3,2-b]carbazole-5,11-diones (3) or (4). Structural assignment of the regioisomers is made by 1H-NMR NOE DIFF experiments. The orientation of the cycloadditions is under control of the bromine atom position on quinones (8) or (9). Calculations by the semiempirical method PM3 of the HOMO and LUMO orbital coefficients of azadienes (1) and quinones (2c), (8) and (9) indicate that the larger ones are situated at C-4 for azadienes (1) and C-3 for the dienophiles.