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In some of these reactions the cycloadducts underwent in situ oxidation to give xanthones, whereas in other cases it was necessary to add DDQ as an oxidant. The reactions of 3\u2010styrylchromones with <jats:italic>N<\/jats:italic>\u2010methyl\u2010 and <jats:italic>N<\/jats:italic>\u2010phenylmaleimide gave the cycloadducts 4\u2010aryl\u20101,3\u2010dioxo\u20103a,4,11a,11b\u2010tetrahydropyrrolo[3,4\u2010<jats:italic>c<\/jats:italic>]xanthones, which were oxidised to 4\u2010aryl\u20101,3\u2010dioxopyrrolo[3,4\u2010<jats:italic>c<\/jats:italic>]xanthones with DDQ. The reactions of 3\u2010styrylchromones with 2\u2010(2\u2010nitrovinyl)thiophene gave 2\u2010aryl\u20103\u2010(2\u2010thienyl)xanthones directly through a Diels\u2013Alder reaction followed by HNO<jats:sub>2<\/jats:sub> elimination and oxidation. The cycloaddition reactions of 3\u2010styrylchromones described herein are stereoselective. The reactions of (<jats:italic>Z<\/jats:italic>)\u2010 and (<jats:italic>E<\/jats:italic>)\u20103\u2010styrylchromones with <jats:italic>N<\/jats:italic>\u2010methylmaleimide gave, respectively, the <jats:italic>endo<\/jats:italic> and <jats:italic>exo<\/jats:italic> cycloadducts, while reactions of (<jats:italic>Z<\/jats:italic>)\u20103\u2010styrylchromones with the less reactive dienophile <jats:italic>N<\/jats:italic>\u2010phenylmaleimide gave a mixture of compounds. This mixture contained the expected <jats:italic>endo<\/jats:italic> cycloadduct and another compound that was identified as the <jats:italic>exo<\/jats:italic> adduct of the reaction between the (<jats:italic>E<\/jats:italic>)\u20103\u2010styrylchromone \u2014 obtained in situ from the isomerisation of its (<jats:italic>Z<\/jats:italic>) isomer \u2014 and <jats:italic>N<\/jats:italic>\u2010phenylmaleimide. The regio\u2010 and stereoselectivity of these cycloaddition reactions have been studied by ab initio calculations and can be understood in terms of a thermodynamically controlled reaction. Theoretical calculations are in complete agreement with the experimental results. (\u00a9 Wiley\u2010VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2005)<\/jats:p>","DOI":"10.1002\/ejoc.200500073","type":"journal-article","created":{"date-parts":[[2005,7,4]],"date-time":"2005-07-04T11:08:06Z","timestamp":1120475286000},"page":"2973-2986","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":22,"title":["Reactivity of 3\u2010Styrylchromones as Dienes in Diels\u2013Alder Reactions under Microwave Irradiation: A New Synthesis of Xanthones"],"prefix":"10.1002","volume":"2005","author":[{"given":"Diana C. G. A.","family":"Pinto","sequence":"first","affiliation":[]},{"given":"Artur M. 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