6344-61-2Relevant articles and documents
Solvolysis and ring closure of quinone methides photogenerated from biaryl systems
Shi, Yijian,Wan, Peter
, p. 1306 - 1323 (2007/10/03)
A variety of biaryl quinone methides have been photogenerated with a range of efficiencies from biaryl precursors 4-6 and 8, 10, and 11, all having hydroxyl and hydroxymethyl substituents on alternate rings. These novel biaryl quinone methides, which cannot be readily generated via thermal chemistry, are trapped by added nucleophiles such as MeOH and ethanolamine; two that cannot undergo electrocyclic ring closure (from 8 and 11) are readily observable by nanosecond laser photolysis, with long wavelength maxima (λ max) of 600 and 520 nm, respectively. Photogenerated o,o′-biaryl quinone methides undergo electrocyclic ring closure to give the corresponding chromene (pyran) products in high yield. Since the precursor biaryl alcohols have highly twisted structures in the ground state (dihedral angle of up to 90° by molecular mechanics calculations), a significant twisting motion to planarity is required to achieve reaction. Using steady-state fluorescence studies, we present evidence to suggest that the mechanism of quinone methide formation may occur via one of the following mechanisms: (i) dissociation of the proton from ArOH that precedes twisting; or (ii) ArOH dissociation and twisting taking place either simultaneously or in quick succession.
Oxidation catalytic system and oxidation process using the same
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, (2008/06/13)
A substrate (e.g., a cycloalkane, a polycyclic hydrocarbon, an aromatic compound having a methyl group or methylene group adjacent to an aromatic ring) is oxidized with oxygen in the presence of an oxidation catalyst comprising an imide compound of the following formula (1) (e.g., N-hydroxyphthalimide), and a co-catalyst (except phosphovanadomolybdic acid) containing an element selected from the group consisting of Group 2A elements of the Periodic Table of Elements, transition metals (Group 3A to 7A elements, Group 8 elements, Group 1B elements and Group 2B elements of the Periodic Table of Elements) and Group 3B elements of the Periodic Table of Elements, for the formation of an oxide (e.g., a ketone, an alcohol, a carboxylic acid): STR1 wherein R1 and R2 represent a substituent such as a hydrogen atom or a halogen atom, or R1 and R2 may together form a double bond or an aromatic or nonaromatic 5- to 12-membered ring, X is O or OH, and n is 1 to 3.
Gas-phase Reactions of 2-Benzyl- and 2-Benzoyl-phenoxyl Radicals, and of 2-Phenoxybenzyl Radicals: Examples of New Hydrogen-transfer Processes
Cadogan, J. I. G.,Hutchison, H. Susan,McNab, Hamish
, p. 385 - 393 (2007/10/02)
Generation of the 2-benzylphenoxyl radical 23 or the 2-phenoxybenzyl radical 24 by flash vacuum pyrolysis of the ethers 8 or 9, or the oxalate 19, respectively, leads to fluoren-1-ol 22 together with 2-benzylphenol 7 and a low yield of xanthene 21.Pyrolysis of the para-substituted derivatives 11 and 20 gives an analogous distribution of products, including two isomeric methylxanthenes 28 and 29 formed via the spirodienyl 27.The reactions of the corresponding 2-benzoylphenoxyl radicals give information on the mechanism of these processes.Thus the formation of the fluorenones 37 and 43 provides evidence for the hydrogen-abstraction mechanism (Scheme 4) of fluorene formation.Secondly, a detailed study of the ratios of xanthones 41 and 42 under a variety of pyrolysis conditions suggests that such 6-membered-ring products are formed by sigmatropic shifts in the spirodienyl, rather than direct cyclisation of the phenoxyl or benzoyl radicals.
