Photochemical rearrangement of dibenzo[1,4]dioxins proceeds through reactive spirocyclohexadienone and biphenylquinone intermediates.
Photochemical studies on a range of model dibenzo[1,4]dioxins were performed in aqueous and organic solutions. The compounds were found to undergo a photochemically initiated aryl-ether bond homolysis that yields reactive 2-spiro-6'-cyclohexa-2',4'-dien-1'-one and subsequent 2,2'-biphenylquinone intermediates. Under steady-state irradiation, the 2,2'-biphenylquinones were observed to participate in excited state hydrogen abstraction from the organic solvent to give the corresponding 2,2'-dihydroxybiphenyls. In the absence of continued irradiation, 2,2'-biphenylquinones with electron donating substituents thermally rearrange to the corresponding oxepino[2,3-b]benzofurans, whereas the unsubstituted 2,2'-biphenylquinone and its derivatives with electron withdrawing groups thermally rearrange to the corresponding 1-hydroxydibenzofurans.
Rayne
Sierra
S
Department of Chemistry, University of Victoria, P.O. Box 3065, Victoria, British Columbia, CanadaV8W 3V6.
Sasaki
Ryan
R
Wan
Peter
P
D001713:Biphenyl Compounds / Q000737:chemistry* / Q000378:metabolism; D002152:Calorimetry, Differential Scanning; D003510:Cyclohexanes / Q000737:chemistry*; D004147:Dioxins / Q000737:chemistry*; D004785:Environmental Pollutants / Q000032:analysis; D010636:Phenols / Q000737:chemistry*; D010777:Photochemistry; D011809:Quinones / Q000737:chemistry* / Q000378:metabolism; D013057:Spectrum Analysis; D013141:Spiro Compounds / Q000737:chemistry*
C507696:2-spiro-6'-cyclohexa-2',4'-dien-1'-one; D001713:Biphenyl Compounds; D003510:Cyclohexanes; D004147:Dioxins; D004785:Environmental Pollutants; D010636:Phenols; D011809:Quinones; D013141:Spiro Compounds; C020887:dibenzo(1,4)dioxin; C038764:2,2'-biphenol