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DOI: 10.1055/s-1991-26385
Oxokohlenstoffe und verwandte Verbindungen; 17. Mitteilung.1 3-Chlor-3-cyclobuten-1,2-dion, ein hochreaktives Dienophil; einfache Synthese von Bicyclo[4.2.0]octa-1(6),3-dien-7,8-dionen und Benzocyclobutendionen
Publikationsverlauf
Publikationsdatum:
17. September 2002 (online)
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Oxocarbons and Related Compounds; Part 17.1 3-Chloro-3-cyclobutene-1,2-dione, a Highly Reactive Dienophile; Simple Synthesis of Bicyclo[4.2.0] octa-1(6),3-diene-7,8-diones and Benzocyclobutenediones 3-Chloro-3-cyclobutene-1,2-dione (1c) reacts with the dienes 3a-e on careful heating to 110°C to afford the bicyclo[4.2.0]octa-1(6), 3-diene-7,8-diones 4a-e. The reaction pathway is explained by Diels-Alder adduct formation and subsequent elimination of hydrogen chloride. 4a-e are readily oxidized by activated manganese(IV) oxide to give the benzocyclobutenediones 5a-e in good yields. The parent benzocyclobutenedione (5a) has been prepared even more conveniently in a "one-pot" Diels-Alder route by heating a mixture of 3-Chloro-3-cyclobutene-1,2-dione (1c) and 1-acetoxy-1,3-butadiene (3f).