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Article: Photoreactions of 3-Diazo-3H-benzofuran-2-one; Dimerization and Hydrolysis of Its Primary Photoproduct, A Quinonoid Cumulenone: A Study by Time-Resolved Optical and Infrared Spectroscopy

TitlePhotoreactions of 3-Diazo-3H-benzofuran-2-one; Dimerization and Hydrolysis of Its Primary Photoproduct, A Quinonoid Cumulenone: A Study by Time-Resolved Optical and Infrared Spectroscopy
Authors
Issue Date2003
PublisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/journals/jacsat/index.html
Citation
Journal Of The American Chemical Society, 2003, v. 125 n. 42, p. 12872-12880 How to Cite?
AbstractLight-induced deazotization of 3-diazo-3H-benzofuran-2-one (1) in solution is accompanied by facile (CO)-O bond cleavage yielding 6-(oxoethenylidene)-2,4-cyclohexadien-1-one (3), which appears with a rise time of 28 ps. The expected Wolff-rearrangement product, 7-oxabicyclo[4.2.0]octa-1,3,5-trien-8-ylidenemethanone (4), is not formed. The efficient light-induced formation of the quinonoid cumulenone 3 opens the way to determine the reactivity of a cumulenone in solution. The reaction kinetics of 3 were monitored by nanosecond flash photolysis with optical (λ max ≈ 460 nm) as well as Raman (1526 cm -1) and IR detection (2050 cm -1). Remarkably, the reactivity of 3 is that expected from its valence isomer, the cyclic carbene 3H-benzofuran-2-one-3-ylidene, 2. In aqueous solution, acid-catalyzed addition of water forms the lactone 3-hydroxy-3H-benzofuran-2-one (5). The reaction is initiated by protonation of the cumulenone on its β-carbon atom. In hexane, cumulenone 3 dimerizes to isoxindigo ((E)-[3,3′ ]bibenzofuranylidene-2,2′-dione, 7), coumestan (6H-benzofuro[3,2-c][1]benzopyran-6-one, 8), and a small amount of dibenzonaphthyrone ([1]benzopyrano[4,3-][1]benzopyran-5,11-dione, 9) at a nearly diffusion-controlled rate. Ab initio calculations (G3) are consistent with the observed data. Carbene 2 is predicted to have a singlet ground state, which undergoes very facile, strongly exothermic (irreversible) ring opening to the cumulenone 3. The calculated barrier to formation of 4 (Wolff-rearrangement) is prohibitive. DFT calculations indicate that protonation of 3 on the β-carbon is accompanied by cyclization to the protonated carbene 2H +, and that dimerization of 3 to 7 and 9 takes place in a single step with negligible activation energy.
Persistent Identifierhttp://hdl.handle.net/10722/70432
ISSN
2015 Impact Factor: 13.038
2015 SCImago Journal Rankings: 7.123
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorChiang, Yen_HK
dc.contributor.authorGaplovsky, Men_HK
dc.contributor.authorKresge, AJen_HK
dc.contributor.authorLeung, KHen_HK
dc.contributor.authorLey, Cen_HK
dc.contributor.authorMac, Men_HK
dc.contributor.authorPersy, Gen_HK
dc.contributor.authorPhillips, DLen_HK
dc.contributor.authorPopik, VVen_HK
dc.contributor.authorRödig, Cen_HK
dc.contributor.authorWirz, Jen_HK
dc.contributor.authorZhu, Yen_HK
dc.date.accessioned2010-09-06T06:22:49Z-
dc.date.available2010-09-06T06:22:49Z-
dc.date.issued2003en_HK
dc.identifier.citationJournal Of The American Chemical Society, 2003, v. 125 n. 42, p. 12872-12880en_HK
dc.identifier.issn0002-7863en_HK
dc.identifier.urihttp://hdl.handle.net/10722/70432-
dc.description.abstractLight-induced deazotization of 3-diazo-3H-benzofuran-2-one (1) in solution is accompanied by facile (CO)-O bond cleavage yielding 6-(oxoethenylidene)-2,4-cyclohexadien-1-one (3), which appears with a rise time of 28 ps. The expected Wolff-rearrangement product, 7-oxabicyclo[4.2.0]octa-1,3,5-trien-8-ylidenemethanone (4), is not formed. The efficient light-induced formation of the quinonoid cumulenone 3 opens the way to determine the reactivity of a cumulenone in solution. The reaction kinetics of 3 were monitored by nanosecond flash photolysis with optical (λ max ≈ 460 nm) as well as Raman (1526 cm -1) and IR detection (2050 cm -1). Remarkably, the reactivity of 3 is that expected from its valence isomer, the cyclic carbene 3H-benzofuran-2-one-3-ylidene, 2. In aqueous solution, acid-catalyzed addition of water forms the lactone 3-hydroxy-3H-benzofuran-2-one (5). The reaction is initiated by protonation of the cumulenone on its β-carbon atom. In hexane, cumulenone 3 dimerizes to isoxindigo ((E)-[3,3′ ]bibenzofuranylidene-2,2′-dione, 7), coumestan (6H-benzofuro[3,2-c][1]benzopyran-6-one, 8), and a small amount of dibenzonaphthyrone ([1]benzopyrano[4,3-][1]benzopyran-5,11-dione, 9) at a nearly diffusion-controlled rate. Ab initio calculations (G3) are consistent with the observed data. Carbene 2 is predicted to have a singlet ground state, which undergoes very facile, strongly exothermic (irreversible) ring opening to the cumulenone 3. The calculated barrier to formation of 4 (Wolff-rearrangement) is prohibitive. DFT calculations indicate that protonation of 3 on the β-carbon is accompanied by cyclization to the protonated carbene 2H +, and that dimerization of 3 to 7 and 9 takes place in a single step with negligible activation energy.en_HK
dc.languageengen_HK
dc.publisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/journals/jacsat/index.htmlen_HK
dc.relation.ispartofJournal of the American Chemical Societyen_HK
dc.titlePhotoreactions of 3-Diazo-3H-benzofuran-2-one; Dimerization and Hydrolysis of Its Primary Photoproduct, A Quinonoid Cumulenone: A Study by Time-Resolved Optical and Infrared Spectroscopyen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0002-7863&volume=125&spage=12872&epage=12880&date=2003&atitle=Photoreactions+of+3-Diazo-3H-benzofuran-2-one;+dimerization+and+hydrolysis+of+its+primary+photoproduct,+a+quinonoid+cumulenone:+a+study+by+time-resolved+optical+and+infrared+spectroscopy++en_HK
dc.identifier.emailPhillips, DL:phillips@hku.hken_HK
dc.identifier.authorityPhillips, DL=rp00770en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1021/ja0365476en_HK
dc.identifier.scopuseid_2-s2.0-10744225801en_HK
dc.identifier.hkuros92461en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-10744225801&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume125en_HK
dc.identifier.issue42en_HK
dc.identifier.spage12872en_HK
dc.identifier.epage12880en_HK
dc.identifier.isiWOS:000185990300048-
dc.publisher.placeUnited Statesen_HK
dc.identifier.scopusauthoridChiang, Y=7201593533en_HK
dc.identifier.scopusauthoridGaplovsky, M=6507254427en_HK
dc.identifier.scopusauthoridKresge, AJ=7005589084en_HK
dc.identifier.scopusauthoridLeung, KH=7401860609en_HK
dc.identifier.scopusauthoridLey, C=7005238686en_HK
dc.identifier.scopusauthoridMac, M=7003388142en_HK
dc.identifier.scopusauthoridPersy, G=6603255350en_HK
dc.identifier.scopusauthoridPhillips, DL=7404519365en_HK
dc.identifier.scopusauthoridPopik, VV=7003701709en_HK
dc.identifier.scopusauthoridRödig, C=55194084900en_HK
dc.identifier.scopusauthoridWirz, J=34573960100en_HK
dc.identifier.scopusauthoridZhu, Y=7406073580en_HK

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