5623-46-1Relevant articles and documents
Photogeneration and chemistry of biphenyl quinone methides from hydroxybiphenyl methanols
Xu, Musheng,Lukeman, Matthew,Wan, Peter
, p. 50 - 56 (2008/02/11)
The photosolvolysis of several biphenyl methanols (Ph-PhCH[Ph]OH) substituted with hydroxy or methoxy groups on the benzene ring not containing the -CH(Ph)OH moiety has been studied in aqueous solution. This work is a continuation of our studies of photosolvolysis of hydroxy-substituted arylmethanols that generate quinone methide intermediates, some of which are known to be relevant intermediates in toxicology and in biological and organic chemistry in general. In this study, we further probe the ability of the biphenyl ring system to transmit charge from the ring substituted with a potential electron-donating group (hydroxy and methoxy) to the adjacent benzene ring that contains a labile benzyl alcohol moiety. We show that in systems with a hydroxy substituent, biphenyl quinone methides (BQM) are the first formed intermediates that are detectable by nanosecond laser flash photolysis, and are responsible for the observed overall photosolvolysis reaction of these compounds. The highly conjugated BQM are found to absorb at long wavelengths (λmax 580 and ~750 nm for the p,p′ and o,p′-isomers, respectively) with relatively long lifetimes in neutral aqueous solution (500 and 30 μs, respectively). The BQM from the o,p′-isomer was found to undergo a competing intramolecular Friedel-Crafts alkylation, to give a fluorene derivative.
Electrochemically Catalyzed Aromatic Nucleophilic Substitution. Phenoxide Ion as Nucleophile
Alam, Nayat,Amatore, Christian,Comballas, Catherine,Pinson, Jean,Saveant, Jean-Michel,et al.
, p. 1496 - 1504 (2007/10/02)
Cyclic voltammetry and preparative-scale electrolysis of aryl halides in the presence of phenoxide ions, a nucleophile reputed as unreactive SRN1 reactions, show the formation, in liquid ammonia or in dimethyl sulfoxide, of coupling products along an electrochemically catalyzed SRN1 aromatic substitution process.Coupling occurs at carbons of the phenyl ring rather than at the phenolic oxygen.The mechanism of the reaction is estabilished on kinetic grounds.Determination of the coupling rate constant between phenoxide ions and aryl radicals and comparison with other n ucleophiles shows that phenoxide ions are quite efficient nucleophiles in SRN1 reactions.The reaction can as well be viewed as an homolytic aromatic substitution.Mechanistic implications concerning the latter type of reaction are discussed.With mediated electrochemical induction of the substitution reaction, it is possible to raise the yield in coupling product up to about 80percent, which renders the reaction an attractive route to the synthesis of electron donor-electron acceptor biaryls.