27890-67-1Relevant articles and documents
Photocondensation of o-Hydroxybenzyl Alcohol in an Alkaline Medium: Synthesis of Phenol-Formaldehyde Resins
Wan, Peter,Hennig, Darren
, p. 939 - 941 (1987)
A new method for the synthesis of phenol-formaldehyde (Bakelite) resins via a new photochemical reaction, the photocondensation of o-hydroxybenzyl alcohol (saligenin) in an alkaline medium, is reported.
The syntheses of 6-methylene-2,4-cyclohexadien-1-imine and related o-quinonoids by FVT of 1-hetero-1,2,3,4-tetrahydronaphthalenes
Letulle,Guenot,Ripoll
, p. 2013 - 2016 (1991)
Flash vacuum thermolysis (~ 1000 °C/10-5 hPa) of 1,2,3,4-tetrahydroquinoline chroman, and thiochroman led upon loss of ethylene (retro-Diels-Alder reaction) to the o-quinonoids 1-3. These reactive monomers were identified by IR-UV at -196 °C and/or MS/MS.
o-Quinone methide as a common intermediate in the pyrolysis of o-hydroxybenzyl alcohol, chroman and 1,4-benzodioxin
Dorrestijn, Edwin,Epema, Onno J.,Van Scheppingen, Wibo B.,Mulder, Peter
, p. 1173 - 1178 (1998)
The product composition in the very low pressure pyrolysis (550-1210 K) of o-hydroxybenzyl alcohol (HBA), 3,4-dihydro-2H-1-benzopyran (chroman), and 1,4-benzodioxin (BD) indicates that o-quinone methide (o-QM) is the common intermediate in each case. At complete conversion of HBA, o-QM was observed as the only product and the mass spectrum of o-QM could be obtained. At higher temperatures (>950 K), o-QM is subsequently converted into benzene and CO. The thermolysis process for chroman starts with cleavage of the phenoxy-carbon bond and proceeds with ethene elimination, yielding o-QM. The high pressure rate parameters for unimolecular decay have been determined to obey kchroman/s-1 = 1015.3 exp (-269/RT). For BD only the cleavage of the phenyl-vinoxy bond has been observed, and after rearrangement and CO elimination o-QM is formed. The Arrhenius equation for the overall rate of disappearance has been found as kBD/s-1 = 1015.6 exp (-310/RT). Ultimately (1100 K) the thermolysis of BD leads to 1 mole of benzene and 2 moles of CO.
Discovery of Novel N-(4-Hydroxybenzyl)valine Hemoglobin Adducts in Human Blood
Degner, Amanda,Carlsson, Henrik,Karlsson, Isabella,Eriksson, Johan,Pujari, Suresh S.,Tretyakova, Natalia Y.,T?rnqvist, Margareta
, p. 1305 - 1314 (2018/12/11)
Humans are exposed to a wide range of electrophilic compounds present in our diet and environment or formed endogenously as part of normal physiological processes. These electrophiles can modify nucleophilic sites of proteins and DNA to form covalent addu
Contrasting Photolytic and Thermal Decomposition of Phenyl Azidoformate: The Curtius Rearrangement Versus Intramolecular C-H Amination
Wan, Huabin,Xu, Jian,Liu, Qian,Li, Hongmin,Lu, Yan,Abe, Manabu,Zeng, Xiaoqing
, p. 8604 - 8613 (2017/11/24)
The decomposition of phenyl azidoformate, PhOC(O)N3, was studied by combining matrix isolation spectroscopy and quantum chemical calculations. Upon UV laser photolysis (193 and 266 nm), the azide isolated in cryogenic noble gas matrices (Ne and Ar, 2.8 K) decomposes into N2 and a novel oxycarbonylnitrene PhOC(O)N, which was identified by matrix-isolation IR spectroscopy (with 15N labeling) and EPR spectroscopy (|D/hc| = 1.620 cm-1 and |E/hc| = 0.024 cm-1). Subsequent visible-light irradiation (532 nm) causes rearrangement of the nitrene into phenoxy isocyanate PhONCO with complex secondary fragmentation (PhO· + ·NCO) and radical recombination species in matrices. The observation of PhONCO provides solid evidence for the Curtius rearrangement of phenyl azidoformate. In sharp contrast, flash vacuum pyrolysis (FVP) of PhOC(O)N3 at 550 K yields N2 and exclusively the intramolecular C-H amination product 3H-benzooxazol-2-one. FVP at higher temperature (700 K) leads to further dissociation into CO2, HNCO, and ring-contraction products. To account for the very different photolytic and thermal decomposition products, the underlying mechanisms for the Curtius rearrangement (concerted and stepwise) of PhOC(O)N3 and the intramolecular C-H amination of the nitrene in both singlet and triplet states are discussed with the aid of quantum chemical calculations using the B3LYP, CBS-QB3, and CASPT2 methods.
Reaction of β-vinyl-meso-tetraphenylporphyrin with o-quinone methides
Menezes, José C. J. M. D. S.,Gomes, Ana T. P. C.,Silva, Artur M. S.,Faustino, Maria A. F.,Neves, Maria G. P. M. S.,Tomé, Augusto C.,De C. Da Silva, Fernando,Ferreira, Vitor F.,Cavaleiro, José A. S.
body text, p. 1841 - 1844 (2011/10/01)
The hetero-Diels-Alder reaction of β-vinyl-meso- tetraphenylporphyrinatozinc(II) with quinone methides generated in situ from Knoevenagel reaction of 2-hydroxy-1,4-naphthoquinone, 4-hydroxycoumarin, and 4-hydroxy-6-methylcoumarin with paraformaldehyde and
Generation and application of o-Quinone methides bearing various substituents on the benzene ring
Sugimoto, Hiromichi,Nakamura, Satoshi,Ohwada, Tomohiko
, p. 669 - 679 (2008/02/09)
o-Quinone methides (o-QMs) are highly reactive, short-lived intermediates, which have potential synthetic applicability. However, few studies on the generation of o-QMs bearing an electron-withdrawing group have been reported. Herein we present a general method for the generation of o-QMs, particularly those substituted with an 0lectrophilic substituent, from new precursors, 4H-1,2-benzoxazines 2. We have also studied systematically the Diels-Alder reactions of o-QMs with various dienophiles, such as vinyl ethers, enamines and imines. The reactions provide a versatile route to substituted chromans, phenols and 3,4-dihydro-2H-benzo[e]-[1,3]oxazines (3,4-dihydro-1,3-benzoxazines). Furthermore, we applied the new method to the derivatization of some natural products.
Retro-Diels-Alder reaction of 4H-1,2-benzoxazines to generate o-quinone methides: Involvement of highly polarized transition states
Sugimoto, Hiromichi,Nakamura, Satoshi,Ohwada, Tomohiko
, p. 10088 - 10095 (2008/04/12)
(Chemical Equation Presented) Here, we describe mechanistic studies of the retro-Diels-Alder reaction of 4H-1,2-benzoxazines bearing various substituents on the benzene ring. 4H-1,2-Benzoxazines are very simple, but quite new, heterocyclic compounds that afford substituted o-quinone methides (o-QMs) through retro-Diels-Alder reaction under mild thermal conditions. The resultant o-QMs undergo Diels-Alder reaction in situ with dienophiles to give phenol and chroman derivatives. The mechanism of the generation of o-QMs has been little studied. Our experimental and density functional theory (DFT) studies have yielded the following results. (1) The generation of o-QMs, i.e., the retro-hetero-Diels-Alder reaction of 4H-1,2-benzoxazines, is rate determining, rather than the subsequent Diels-Alder reaction of the resultant o-QM with dienophiles. (2) The reaction rate is strongly influenced by the electronic features of substituents and the polarity of the solvent. The reaction proceeds faster in a polar solvent such as dimethyl sulfoxide, probably because of stabilization of the electronically polarized TS structure. (3) The reactions show characteristic positional effects of substitution on the benzene ring. While an electron-withdrawing group such as CF3 at C5, C6, or C7 positions decelerates the reaction, the same substituent at C8 accelerates the reaction, compared with the reaction of unsubstituted 4H-1,2-benzoxazine. In particular, substitution at C5 significantly decelerates the reaction as compared with the unsubstituted case. This is due to the difference in the inductive effect of CF3 at the different positions. Similar positional effects occur with a halogen (Cl) and a nitro group. All these data support the involvement of polarized TS structures, in which the O-N bond cleavage precedes the C-C bond cleavage.
Substituents on quinone methides strongly modulate formation and stability of their nucleophilic adducts
Weinert, Emily E.,Dondi, Ruggero,Colloredo-Melz, Stefano,Frankenfield, Kristen N.,Mitchell, Charles H.,Freccero, Mauro,Rokita, Steven E.
, p. 11940 - 11947 (2007/10/03)
Electronic perturbation of quinone methides (QM) greatly influences their stability and in turn alters the kinetics and product profile of QM reaction with deoxynucleosides. Consistent with the electron-deficient nature of this reactive intermediate, electron-donating substituents are stabilizing and electron-withdrawing substituents are destabilizing. For example, a dC N3-QM adduct is made stable over the course of observation (7 days) by the presence of an electron-withdrawing ester group that inhibits QM regeneration. Conversely, a related adduct with an electron-donating methyl group is very labile and regenerates its QM with a half-life of approximately 5 h. The generality of these effects is demonstrated with a series of alternative quinone methide precursors (QMP) containing a variety of substituents attached at different positions with respect to the exocyclic methylene. The rates of nucleophilic addition to substituted QMs measured by laser flash photolysis similarly span 5 orders of magnitude with electron-rich species reacting most slowly and electron-deficient species reacting most quickly. The reversibility of QM reaction can now be predictably adjusted for any desired application.
Benzoxetene. Direct observation and theoretical studies
Tomioka, Hideo,Matsushita, Takeshi
, p. 399 - 400 (2007/10/03)
Irradiation of either o-hydroxphenyldiazomethane or benzofuranone in argon matrix at 10 K generates benzoxetene which is in photoequilibrium with o-quinone methide.
