Brito, Cristela

Cavaleiro, José

Esteves, Cátia

Santos, Clementina M.M.

Silva, Artur

Biblioteca Digital do IPB

Recent developments in the syntesis of 1-aryl-9H-xanthen-9-onesCátia I. C. Esteves a, Clementina M. M. Santosa,b, Cristela M. Brito a, Artur M. S. Silva a, José A. S. Cavaleiro aaDepartment of Chemistry & QOPNA, University of Aveiro, 3810-193 Aveiro, PortugalbDepartment of Vegetal Production and Technology, Escola Superior Agrária de Bragança, 5301-855 Bragança, PortugalIntroductionXanthones or 9H-xanthen-9-one (dibenzo- -pirone) are a class of natural oxygenated heterocyclic compounds with a large diversity of functional groups.1 In recent years,several studies have been reported on both natural and synthetic derivatives of this class of compounds due to their wide range of biological and pharmacological properties(include anti-inflammatory, cancerchemopreventive, antibacterial, antimalarial, radical scavenging, cytotoxicity, inhibition of cyclooxygenase, and prostaglandin E2activities).1-3 Some xanthones even surpass the antimicrobial activity of traditional antibiotics.1These promising applications have motivated the search for new derivatives and as a part of an ongoing study we present here the latest developments on the synthesis of1-aryl-9H-xanthen-9-ones 5a-e. The methodology involves the condensation of 2-methyl-4H-chromen-4-one 1 with cinnamaldehydes 3a-e (3a commercially available and3b-e prepared from the corresponding halobenzenes), to afford the (E,E)-2-(4-arylbuta-1,3-dien-1-yl)-4H-chromen-4-ones 4a-e.4 The final step consists in theelectrocyclization and oxidation reactions giving rise to the desired xanthones 5a-e. It was performed by refluxing chromones 4a-e in trichlorobenzene with a catalyticamount of iodine.Details on the synthesis and structural characterization of compounds 4 and 5 are presented and discussed.AcknowledgementsThanks are due to University of Aveiro, FCT and FEDER for funding the Organic Chemistry Research Unit. One of us (C. I. C. Esteves) is also grateful for the financial support through projectSFRH/BI/51098/2010.General ProcedureEncontro Luso-Galego de Química 10 - 12 November 2010, Aveiro, PortugalReferences(1) Franklin G., Conceição L. F. R., Kombrink E., Dias A. C. P. Phytochem. 2009, 70, 60.(2) Ngoupayo J., Tabopda T. K., Ali M. S., Bioorg. Med. Chem. 2009, 17, 5688.(3) Brase S., Encinas A., Keck J., Nising C. F. Chem. Rev. 2009, 109, 3960.(4) The results reported here are an improvement of those already reported by Brito C. M., Master Thesis, Universidade de Aveiro, 2009%ULWR&06LOYD$06&DYDOHLUR-$6´1HZURXWHVWRWKHsynthesis of 1-aryl-9H-xanthen-9-RQHVµ3<&KHP8QLYHUVLGDGHGH$YHLUR2010.OORCHORORO1 3a-e 4a-e 5a-eO CH3OB Ca R = H b R = CH3c R = OCH3d R = Br e R = NO2A: Dry DMF, 90ºC.B: EtOH, NaOEt (4eq.), r.t., 4h (4a-d), EtOH, NaOEt (1 eq.), r.t., 54h (4e).C: TCB, I2, reflux, 48h.Cinnamaldehyde Product ǃ3a 4a 803b 4b 773c 4c 833d 4d 703e 4e 68Reaction BChromone Product ǃ4a 5a 304b 5b 264c 5c 704d 5d 564e 5e 50Reaction CStructural ElucidationOOBr23456789101'2'3'4'5'6'Benzene derivative Product ǃ2b 3b 632c 3c 682d 3d 332e 3e 69Reaction AOBrO12344a4b56788a 9 9a1'2'3'4'5'6'O CH3OOH OCH3COCldry Py92%OOOdry THF, NaHReflux 1hr.t. 12h51%OH O O OH O OHDMSO, Ac. TsOH100ºC 2h79%17.17.27.37.47.57.67.77.87.98.08.18.2 ppm6H-8H-6H-3H-¶¶H-4H-5H-7H-¶¶H-26.46.66.87.07.27.47.67.88.08.2 ppm3H-5 H-7H-8H-¶¶H- H-H-H-3H-6H-¶¶C-3C-6C-¶¶C-¶¶C-2C-8C-7C-4C-5H-2H-¶¶H-7H-5H-4H-¶¶H-3H-6H-81H NMR1H NMR13C NMRHMBCHSQCC-9C-4aC-4bC-1C-C-8aC-C-9aH-8 H-6H-3H-¶¶H-4H-5 H-7H-¶¶H-2ORO1234a4b5678 8a9 9a1'2'3'4'5'6'HHHHHHHHHH4H10HMBC ConectivitiesC-4C-2C-9C-3C-8C-C-C-7C-C-¶¶C-¶¶C-C-C-6C-C-C-5CHORRXX = Br or IOOTBAA, K2CO3, KClPd(CH3COO)2 3a-eA2a-e

Recent developments in the synthesis of 1-aryl-9H-xanthen-9-ones

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Recent developments in the synthesis of 1-aryl-9H-xanthen-9-ones

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