Hetero Diels-Alder reactions of 1-acetylamino- and 1-dimethylamino-1-azadienes with benzoquinones

Treatment of bromobenzoquinone with 2 equiv. of a 1-dimethylamino-1-azadien e afforded mixtures of the corresponding 1,8-diaza-9,10-anthraquinone and 1 ,5-diaza-9, 10-anthraquinone. Double hetero Diels-Alder reactions between 1 -dimethylamino-1-azadienes and 2,6-dibromobenzoquinone afford symmetrically substituted 1,8-diaza-9,10-anthraquinone derivatives in excellent yields. 3-Substituted 1-azadienes afford aromatic derivatives, while 4-substituted or 3,4-disubstituted 1-azadienes lead to 1,8-bis-(dimethylamino)-1,4,5,8-te trahydro-1,8-diaza-9,10-anthraquinones, which were aromatized under thermal conditions. The hetero Diels-Alder reactions could also be controlled to g ive isolated 7-bromo-5,8-quinolinequinones, whose treatment with a second a zadiene allowed the preparation of unsymmetrical 1,8-diaza-9, 10-anthraquin ones. (C) 2000 Elsevier Science Ltd. All rights reserved.