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Benzopyran
About: Benzopyran is a research topic. Over the lifetime, 1889 publications have been published within this topic receiving 15235 citations.
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TL;DR: In this article, benzo-fused heterocycles such as indoles, benzofurans, and a benzopyran were obtained using an intramolecular cross-coupling of vinyl halides with phenols.
Abstract: Substituted benzo-fused heterocycles such as indoles, benzofurans, and a benzopyran were obtained using an intramolecular cross-coupling of vinyl halides with phenols. This transformation represents a new route to these heterocycles and is accomplished using a palladacyclic catalyst under anionic conditions. © 1997 Elsevier Science Ltd.
TL;DR: The photochemical conversion of 4,4,7,7-tetramethyl into 3,3,6,6-Tramethyl-3,5, 6, 7-Tetrahydrobenzofuran-4(2H)-one in methanol does not - as previously assumed - proceed by decarbonylation of the primarily formed acyl-vinyloxy biradical 2 as discussed by the authors.
Abstract: The photochemical conversion of 4,4,7,7-tetramethyl-4,6,7,8-tetrahydro-2H-benzopyran-2,5(3H)-dione (1) into 3,3,6,6-tetramethyl-3,5,6,7-tetrahydrobenzofuran-4(2H)-one (4) in methanol does not - as previously assumed - proceed by decarbonylation of the primarily formed acyl-vinyloxy biradical 2. This conclusion results from the finding that C-2, i. e. the CH2 group, of benzofuranone 4 stems from the solvent. Similar observations were made for other benzopyrandiones 15. A reaction sequence consisting of (a) ketene elimination from 2 with formation of 2-isopropylidene-5,5-dimethyl-1,3-cyclo-hexanedione and (b) light-induced (reductive) H . and . CH2OH addition to this intermediate followed by cyclization and dehydration to 4, is proposed for the conversion 14.