Publication
Efficient syntheses of new polyhydroxylated 2,3-diaryl-9h-xanthen-9-ones
| dc.contributor.author | Santos, Clementina M.M. | |
| dc.contributor.author | Silva, Artur | |
| dc.contributor.author | Cavaleiro, José | |
| dc.date.accessioned | 2011-02-01T10:31:52Z | |
| dc.date.available | 2011-02-01T10:31:52Z | |
| dc.date.issued | 2009 | |
| dc.description.abstract | A large number of hydroxylated 2,3-diaryl-9H-xanthen-9- ones have been synthesised by two different approaches, starting either from 3-bromo-2-methyl-4H-chromen-4-one or from (E)-3-bromo-2-styryl-4H-chromen-4-ones. The former method involves Heck reactions between 3-bromo-2-methyl- 4H-chromen-4-one and styrenes, leading to (E)-2-methyl-3- styryl-4H-chromen-4-ones; these condensed with benzaldehyde to give (E,E)-2,3-distyryl-4H-chromen-4-ones, which led to the desired 2,3-diaryl-9H-xanthen-9-ones under reflux in 1,2,4-trichlorobenzene. 3-Bromo-2-styryl-4H-chromen-4- ones were obtained either by aldol condensations between 3-bromo-2-methyl-4H-chromen-4-one and benzaldehydes, or through Baker–Venkataraman rearrangements of 2-acetylphenyl cinnamates, followed by one-pot bromination/ cyclisation with phenyltrimethylammonium tribromide. The 2,3-diaryl-9H-xanthene-9-ones were obtained in one-pot transformations involving Heck reactions between (E)-3- Introduction Xanthones constitute one of the major classes of naturally occurring oxygen-containing heterocyclic compounds containing dibenzo-γ-pyrone rings.[1] They occur in two major plant families, Guttiferae and Gentianaceae, and also in some families of fungi and lichens.[2,3] Natural derivatives can be hydroxylated, methoxylated or prenylated, among other possibilities; the parent compound xanthone itself is not known as a natural product.[3,4] The presence of aryl groups on the xanthone core has only been reported for a few synthetic derivatives, and as far as we know the literature had never presented the synthesis of xanthones featuring 2,3-diaryl moieties before our work.[5,6] Over the last decades these substances have been extensively studied not only because they participate in several biological functions but also as a consequence of their remarkable antifungal,[7–9] anti-inflammatory,[10,11] antimalarial[ 12–14] and antitumour activities,[15,16] and even as promising antioxidant agents.[17–19] Structure–activity stud- [a] Department of Vegetal Production and Technology, Escola Superior Agrária de Bragança, 5301-855 Bragança, Portugal Fax: +351-273-325405 E-mail: clems@ipb.pt [b] Department of Chemistry & QOPNA, University of Aveiro, 3810-193 Aveiro, Portugal Fax: +351-234-370084 E-mail: artur.silva@ua.pt © 2009 Wiley-VCH Verlag GmbH 2642 & Co. KGaA, Weinheim Eur. J. Org. Chem. 2009, 2642–2660 bromo-2-styryl-4H-chromen-4-ones and styrenes, followed by electrocyclisation and oxidation processes. The 2,3-diaryl- 3,4-dihydro-9H-xanthene-9-one intermediates were also isolated under these conditions, and so when 5-methoxy-2-styryl- 4H-chromen-4-ones were used as starting materials the 1-hydroxy-6,7-diaryl-9H-xanthene-9-ones were also observed. The second method is a general one, because it allowed the synthesis of a great number of 2,3-diaryl-9Hxanthen- 9-ones with several substitution patterns, whereas the first one is limited to certain derivatives. The last step in the synthesis of hydroxylated 2,3-diaryl-9H-xanthen-9-ones was the cleavage of the hydroxy protecting groups with boron tribromide. The structures and stereochemistry of all new compounds were established by NMR studies. | por |
| dc.identifier.citation | Santos, Clementina; Silva, Artur; Cavaleiro, José (2009). Efficient syntheses of new polyhydroxylated 2,3-diaryl-9h-xanthen-9-ones. European Journal of Organic Chemistry. ISSN 1434-193X. 16, p. 2642-2660 | por |
| dc.identifier.doi | 10.1002/ejoc.200900026 | |
| dc.identifier.issn | 1434-193X | |
| dc.identifier.uri | http://hdl.handle.net/10198/3221 | |
| dc.language.iso | eng | por |
| dc.peerreviewed | yes | por |
| dc.publisher | Wiley | por |
| dc.subject | Xanthones | por |
| dc.subject | Alcohols | por |
| dc.subject | Oxygen heterocycles | por |
| dc.subject | Heck reaction | por |
| dc.subject | NMR spectroscopy | por |
| dc.title | Efficient syntheses of new polyhydroxylated 2,3-diaryl-9h-xanthen-9-ones | por |
| dc.type | journal article | |
| dspace.entity.type | Publication | |
| oaire.citation.endPage | 2660 | por |
| oaire.citation.startPage | 2642 | por |
| oaire.citation.title | European Journal of Organic Chemistry | por |
| person.familyName | Santos | |
| person.givenName | Clementina M.M. | |
| person.identifier.ciencia-id | 9018-DB9C-C590 | |
| person.identifier.orcid | 0000-0003-4380-7990 | |
| person.identifier.scopus-author-id | 7201458663 | |
| rcaap.rights | openAccess | por |
| rcaap.type | article | por |
| relation.isAuthorOfPublication | 64f662b6-775d-4ea0-bfd7-f527af0ac1a0 | |
| relation.isAuthorOfPublication.latestForDiscovery | 64f662b6-775d-4ea0-bfd7-f527af0ac1a0 |