Photooxygenolysis of 3,6-di-tert-butyl-o-benzoquinone
摘要:
The photolysis of 3,6- and 3,5-di-tert-butyl-o-benzoquinones in benzene (lambda > 380 nm, inert atmosphere) involves decarbonylation of the compounds to furnish respectively 2,5- and 2,4-di-tert-butylcyclopentadienones. The 2,5-isomer is stable, and the 2,4-di-tert-butylcyclopentadienone suffers a conversion into a Diels-Alder adduct. The participation of oxygen inhibited the decarbonylation and changed the direction of the photolysis: Here the products of the 3,5-di-tert-butyl-o-benzoquinones conversion were a di-tert-butylmuconic anhydride and dipivalylethylene. It was concluded that a singlet oxygen was involved in the process which formed by a triplet-triplet annihilation at the interaction of O-3(2) with a triplet-excited initial quinone.
A Doubly Destabilized Antiaromatic Cyclopentadienyl Cation: Solvolysis of a 5-Trifluoroacetoxy-5-heptafluoropropyl 1,3-Cyclopentadiene<sup>1</sup><sup>a</sup>
作者:Annette D. Allen、Thomas T. Tidwell
DOI:10.1021/jo010562g
日期:2001.11.1
formation from 15 and leads to the extensively rearranged fulvene 18, implicating formation of the doubly destabilized cation 20. Carbocation formation from 15 is retarded by a factor of 10(20) relative to the model 11, showing cumulative destabilizing effects due to formation of the antiaromatic cyclopentadienyl carbocation and electron withdrawal by the fluoroalkyl group.
5-三氟乙酰氧基-5-庚氟丙基环戊二烯15重排至异构三氟乙酸酯16,其速率常数比相应的5-CH(3)衍生物5的溶剂分解速率常数小5 x 10(5)。标记15为(18)O显示了通过[1,5]-σ重排发生的重排。溶剂化16的速度比其从15形成的速度慢4倍,并导致重新排列的富勒烯18,这意味着双不稳定阳离子20的形成。相对于15,碳阳离子的形成被延迟10(20)倍。模型11显示出由于形成抗芳族环戊二烯基碳正离子和氟烷基的电子吸收而引起的累积去稳定作用。
CATALYTIC OXIDATION OF DIENONES WITH TPPMn(III)Cl-PhIO SYSTEM
作者:Toshikazu Takata、Rieko Tajima、Wataru Ando
DOI:10.1246/cl.1985.665
日期:1985.5.5
Several dienones were oxidized with iodosylbenzene (PhIO) in the presence of catalytic amount of tetraphenylporphinatomanganese(III) chloride (TPPMn(III)Cl), affording corresponding epoxides and pyrons.
Irradiation of o-benzoquinones with vinyl ethers in acetonitrile gives 2-alkoxy-7-hydroxy-2,3-dihydrobenzofurans in 28–74% yields via regioselective [3 + 2] photoaddition.
Spectroscopy and photochemistry of a series of alkyl-substituted o- and p-benzoquinones and their mono-oxime O-methyl ethers
作者:Frank Stunnenberg、Hans Cerfontain、Roel B. Rexwinkel
DOI:10.1002/recl.19921111005
日期:——
Following our previous reports on the spectroscopy and photochemistry of methyl ethers of cyclic α-oxo oximes, we have now studied a number of o- and p-benzoquinonemono-oximeO-methylethers and, for comparison, some corresponding o- and p-benzoquinones. The ground-state electronic structure of o-benzoquinones is described satisfactorily by the sum of the two propenal fragments. The structure of the