- Redox-neutral functionalization of α-Csp3-H bonds of secondary cyclic amines: a highly atom-economical strategy forN-arylation/formal cross-dehydrogenative couplings
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An efficient redox-neutral method has been developed for α-Csp3-H functionalization of secondary cyclic aminesviaconcurrentN-arylation/formal cross dehydrogenation coupling (CDC) with sp2-C-H and sp3-C-H bonds of arenes an
- Husen, Saddam,Jha, Priyankar,Kumar, Ravindra
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supporting information
p. 2950 - 2955
(2021/05/05)
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- Reductive Aromatization of Quinols with B2pin2 as Deoxidizing Agent
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We have demonstrated B2pin2 as superior deoxidizing agent for the reductive deoxygenation of quinol derivatives under basic conditions. A wide range of highly functionalized phenols were obtained in good yields including a complex drug molecule, which revealed the high functional group tolerance of this protocol.
- Liu, Bin,Xu, Yin,Luo, Zhibin,Xie, Jimin
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supporting information
p. 1022 - 1024
(2020/03/19)
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- Site-selective 1,3-double functionalization of arenes using: Para -quinol, C-N, and C-C/C-P three-component coupling
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A catalytic and site-selective approach has been demonstrated for dual functionalization of arenes via cross-coupling reactions of p-quinols with amines and isocyanides/phosphites. The strategy enables the production of a series of 3-amino-benzamides and
- Husen, Saddam,Chauhan, Anil,Kumar, Ravindra
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supporting information
p. 1119 - 1124
(2020/03/11)
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- Method for selectively preparing hydroquinone monoether compound or quinol compound (by machine translation)
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The method comprises the following steps: taking an organic boric acid compound and a p-benzoquinone compound as a reaction raw material, under the action of a copper catalyst, selectively reacting to obtain a hydroquinone monoether compound or a quinol compound. Compared with the prior art, the method disclosed by the invention adopts a one-pot reaction, can selectively obtain two products through solvent control, is suitable for preparing various types of hydroquinone monoether compounds and quinol compounds, and has wide applicability. The substrate functional group is high in tolerance and wide in substrate range. The raw material and the catalyst are cheap and easily available, the reaction conditions are mild, the reaction solvent is green and environment-friendly, the post-treatment is simple, and the yield and purity of the product are high. The preparation method is convenient. The method is rapid and efficient, and has a good application prospect in drug molecule synthesis. (by machine translation)
- -
-
Paragraph 0113-0116
(2020/12/30)
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- Bio-inspired Domino oxa-Michael/Diels–Alder/oxa-Michael Dimerization of para-Quinols
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A bio-inspired, pyrrolidine-mediated, dimerization of para-quinols has been developed. It represents one of the most complex, yet general, dimerization reactions ever disclosed, selectively forming four new bonds, four new rings, and eight new contiguous stereogenic centres. The para-quinol starting materials are easily handled, bench-stable compounds, accessed in just one step from aromatic feedstocks. The reaction can be scaled up to give grams of polycyclic material, primed for further elaboration.
- Green, Nicholas J.,Connolly, Catherine A.,Rietdijk, Koen P. W.,Nichol, Gary S.,Duarte, Fernanda,Lawrence, Andrew L.
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supporting information
p. 6198 - 6202
(2018/05/30)
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- Phosphazene-catalyzed desymmetrization of cyclohexadienones by dithiane addition
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We report a desymmetrization of cyclohexadienones by intramolecular conjugate addition of a tethered dithiane nucleophile. Mild reaction conditions allow the formation of diversely functionalized fused bicyclic lactones. The products participate in facially selective additions from the convex surface, leading to allylic alcohol derivatives.
- Horwitz, Matthew A.,Massolo, Elisabetta,Johnson, Jeffrey S.
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supporting information
p. 762 - 767
(2017/06/21)
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- Site-Selective Iron(III) Chloride-Catalyzed Arylation of 4-Aryl-4-methoxy-2,5-cyclohexadienones for the Synthesis of Polyarylated Phenols
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The iron(III) chloride-catalyzed Friedel–Crafts arylation of 4-aryl-4-methoxy-2,5-cyclohexadienones, which were easily prepared by the phenyliodine(III) diacetate (PIDA)-mediated oxidation of 4-arylphenols in methanol, proceeded site-selectively to form meta-terphenyl (2,4-diarylphenol) derivatives in good yields. The subsequent PIDA-mediated oxidation and iron(III) chloride-catalyzed Friedel–Crafts arylation of the resulting products gave the corresponding 2,4,6-triarylphenol derivatives. The present method provides useful highly substituted polyarylated compounds. (Figure presented.).
- Sawama, Yoshinari,Masuda, Masahiro,Nakatani, Ryosuke,Yokoyama, Hiroki,Monguchi, Yasunari,Dohi, Toshifumi,Kita, Yasuyuki,Sajiki, Hironao
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supporting information
p. 3683 - 3687
(2016/12/16)
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- Direct spectroscopic observation of closed-shell singlet, open-shell singlet, and triplet p -biphenylyloxenium ion
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The photophysics and photochemistry of p-biphenylyl hydroxylamine hydrochloride was studied using laser flash photolysis ranging from the femtosecond to the microsecond time scale. The singlet excited state of this photoprecursor is formed within 350 fs and partitions into three different transients that are assigned to the p-biphenyloxy radical, the open-shell singlet p-biphenylyloxenium ion, and the triplet p-biphenylyloxenium ion, having lifetimes of 40 μs, 45 ps, and 1.6 ns, respectively, in CH3CN. The open-shell singlet p-biphenylyloxenium ion predominantly undergoes internal conversion to produce the closed-shell singlet p-biphenylyloxenium ion, which has a lifetime of 5-20 ns. The longer-lived radical is unambiguously assigned by nanosecond time-resolved resonance Raman (ns-TR3) spectroscopy, and the assignment of the short-lived singlet and triplet oxenium ion transient absorptions are supported by matching time-dependent density functional theory (TD-DFT) predictions of the absorptions of these species, as well as by product studies that implicate the intermediacy of charged electrophilic intermediates. Product studies from photolysis give p-biphenylol as the major product and a chloride adduct as the major product when NaCl is added as a trap. Thermolysis studies give p-biphenylol as a major product, as well as water, ammonium, and chloro adducts. These studies provide a rare direct look at a discrete oxenium ion intermediate and the first detection of open-shell singlet and triplet configurations of an oxenium ion, as well as providing an intriguing example of the importance of excited state dynamics in governing the electronic state population of reactive intermediates.
- Li, Ming-De,Hanway, Patrick J.,Albright, Toshia R.,Winter, Arthur H.,Phillips, David Lee
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supporting information
p. 12364 - 12370
(2014/12/09)
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- Hypervalent iodine oxidation of phenol derivatives using a catalytic amount of 4-iodophenoxyacetic acid and Oxone as a co-oxidant
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Reaction of p-substituted phenols 2 with a catalytic amount of 4-iodophenoxyacetic acid (1) and Oxone as a co-oxidant in tetrahydrofuran (THF) or 1,4-dioxane-water gave the corresponding p-quinols 3 in excellent yields. Reaction of p-dialkoxyarenes 4 in 2,2,2-trifluoroethanol- water gave the corresponding p-quinones 5 in excellent yield without purification. These reactions provide efficient and practical methods for the preparation of p-quinols and p-quinones from p-substituted phenols and p-dialkoxyarenes, respectively. This quinone synthesis was applied to synthesis of blattellaquinone (13), the sex pheromone of the German cockroach Blattella germanica.
- Yakura, Takayuki,Omoto, Masanori,Yamauchi,Tian, Yuan,Ozono, Ayaka
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experimental part
p. 5833 - 5840
(2010/09/11)
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- Efficient synthesis of p-quinols using catalytic hypervalent iodine oxidation of 4-arylphenols with 4-iodophenoxyacetic acid and oxone
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Efficient synthesis of p-quinols (2) using catalytic hypervalent iodine oxidation of 4-arylphenols (1) with 4-iodophenoxyacetic acid (3) and Oxone was developed. Reaction of 1 with a catalytic amount of 3 in the presence of Oxone as a co-oxidant in tetrahydrofuran or 1,4-dioxane-water gave the corresponding 2 in excellent yields.
- Yakura, Takayuki,Omoto, Masanori
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body text
p. 643 - 645
(2009/12/24)
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- Characterization of reactive intermediates generated during photolysis of 4-acetoxy-4-aryl-2,5-cyclohexadienones: Oxenium ions and aryloxy radicals
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Aryloxenium ions 1 are reactive intermediates that are isoelectronic with the better known arylcarbenium and arylnitrenium ions. They are proposed to be involved in synthetically and industrially useful oxidation reactions of phenols. However, mechanistic studies of these intermediates are limited. Until recently, the lifetimes of these intermediates in solution and their reactivity patterns were unknown. Previously, the quinol esters 2 have been used to generate 1, which were indirectly detected by azide ion trapping to generate azide adducts 4 at the expense of quinols 3, during hydrolysis reactions in the dark. Laser flash photolysis (LFP) of 2b in the presence of O2 in aqueous solution leads to two reactive intermediates with γmax 360 and 460 nm, respectively, while in pure CH3CN only one species with λmax 350 nm is produced. The intermediate with Amax 460 nm was previously identified as lb based on direct observation of its decomposition kinetics in the presence of N3-, comparison to azide ion trapping results from the hydrolysis reactions, and photolysis reaction products (3b). The agreement between the calculated (B3LYP/6-31G(d)) and observed time-resolved resonance Raman (TR3) spectra of 1b further confirms its identity. The second intermediate with λ max 360 nm (350 nm in CH3CN) has been characterized as the radical 5b, based on its photolytic generation in the less polar CH 3CN and on isolated photolysis reaction products (6b and 7b). Only the radical intermediate 5b is generated by photolysis in CH3CN, so its UV-vis spectrum, reaction products, and decay kinetics can be investigated in this solvent without interference from 1b. In addition, the radical 5a was generated by LFP of 2a and was identified by comparison to a published UV-vis spectrum of authentic 5a obtained under similar conditions. The similarity of the UV-vis spectra of 5a and 5b, their reaction products, and the kinetics of their decay confirm the assigned structures. The lifetime of 1b in aqueous solution at room temperature is 170 ns. This intermediate decays with first-order kinetics. The radical intermediate 5b decomposes in a biphasic manner, with lifetimes of 12 and 75 μs. The decay processes of 5a and 5b were successfully modeled with a kinetic scheme that included reversible formation of a dimer. The scheme is similar to the kinetic models applied to describe the decay of other aryloxy radicals.
- Wang, Yue-Ting,Jin, Kyoung Joo,Leopold, Samuel H.,Wang, Jin,Peng, Huo-Lei,Platz, Matthew S.,Xue, Jiadan,Phillips, David Lee,Glover, Stephen A.,Novak, Michael
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experimental part
p. 16021 - 16030
(2009/05/16)
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- Grignard reagents in ionic solvents: Electron transfer reactions and evidence for facile Br-Mg exchange
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Grignard reagents form persistent solutions in phosphonium ionic liquids possessing O-donor anions and these solutions are excellent reaction media for electron transfer processes and transmetallation reactions. The Royal Society of Chemistry.
- Ramnial, Taramatee,Taylor, Stephanie A.,Clyburne, Jason A. C.,Walsby, Charles J.
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p. 2066 - 2068
(2008/02/08)
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- Oxidation of 4-arylphenol trimethylsilyl ethers to p-arylquinols using hypervalent iodine(III) reagents
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An efficient synthesis of p-arylquinols by the oxidation of 4-arylphenol trimethylsilyl ethers with phenyliodine(III) diacetate (PIDA) is reported. This protocol greatly improved the yield of p-quinol by minimizing oligomer side products compared to the o
- Felpin, Fran?ois-Xavier
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p. 409 - 412
(2008/02/04)
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- The hydrolysis of 4-acyloxy-4-substituted-2,5-cyclohexadienones: Limitations of aryloxenium ion chemistry
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The title compounds serve as potential precursors to aryloxenium ions, often proposed, but primarily uncharacterized intermediates in phenol oxidations. The uncatalyzed and acid-catalyzed decomposition of 4-acetoxy-4-phenyl-2,5-cyclohexadienone, 2a, generates the quinol, 3a. 18O-Labeling studies performed in 16O-H2O, and monitored by LC/MS and1 13C NMR spectroscopy that can detect 18O-induced chemical shifts on 13C resonances, show that 3a was generated in both the uncatalyzed and acid-catalyzed reactions by C alkyl-O bond cleavage consistent with formation of an aryloxenium ion. Trapping with N3- and Br- confirms that both uncatalyzed and acid-catalyzed decompositions occur by rate-limiting ionization to form the 4-biphenylyloxenium ion, 1a. This ion has a shorter lifetime in H2O than the corresponding nitrenium ion, 7a (12 ns for 1a, 300 ns for 7a at 30 °C). Similar analyses of the product, 3b, of acid- and base-catalyzed decomposition of 4-acetoxy-4-methyl-2,5-cyclohexadienone, 2b, in 18O-H2O show that these reactions are ester hydrolyses that proceed by Cacyl-O bond cleavage processes not involving the p-tolyloxenium ion, 1b. Uncatalyzed decomposition of the more reactive 4-dichloroacetoxy-4-methyl-2,5-cyclohexadienone, 2b′, is also an ester hydrolysis, but 2b′ undergoes a kinetically second-order reaction with N3- that generates an oxenium ion-like substitution product by an apparent SN2′ mechanism. Estimates based on the lifetimes of 1a, 7a, and the p-tolylnitrenium ion, 7b, and the calculated relative stabilities of these ions toward hydration indicate that the aqueous solution lifetime of 1b is ca. 3-5 ps. Simple 4-alkyl substituted aryloxenium ions are apparently not stable enough in aqueous solution to be competitively trapped by nonsolvent nucleophiles.
- Novak, Michael,Glover, Stephen A.
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p. 8090 - 8097
(2007/10/03)
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- Generation and trapping of the 4-biphenylyloxenium ion by water and azide: Comparisons with the 4-biphenylylnitrenium ion
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Generation of the 4-biphenylyloxenium ion, 1a, from hydrolysis of 4-acetoxy-4-phenyl-2,5-cyclohexadienone, 2a, is demonstrated by common ion rate depression and azide trapping. The ion is less selective with a shorter lifetime (12 ns at 30 °C) in aqueous
- Novak, Michael,Glover, Stephen A.
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p. 7748 - 7749
(2007/10/03)
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- 4-Substituted 4-hydroxycyclohexa-2,5-dien-1-ones with selective activities against colon and renal cancer cell lines
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The synthesis and antitumor evaluation of a series of new heteroaromatic- and aromaticsubstituted hydroxycyclohexadienones ("quinols"), and their imine counterparts, are described. The quinols were synthesized via the addition of a lithiated aromatic moie
- Wells, Geoffrey,Berry, Jane M.,Bradshaw, Tracey D.,Burger, Angelika M.,Seaton, Angela,Wang, Bo,Westwell, Andrew D.,Stevens, Malcolm F. G.
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p. 532 - 541
(2007/10/03)
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- Quinone Alkylation Using Organocadmium Reagents: A General Synthesis of Quinols
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Reactions of p-benzoquinone with organocadmium reagents yield quinols, the result of quinone carbonyl monoalkylation. The reactions proceed in good yield and are devoid of bisaddition and hydroquinone byproducts. Quinone alkylations using this method show
- Aponick, Aaron,McKinley, Jason D.,Raber, Jeffrey C.,Wigal, Carl T.
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p. 2676 - 2678
(2007/10/03)
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- Reactions of ester derivatives of carcinogenic N-(4-biphenylyl)hydroxylamine and the corresponding hydroxamic acid with purine nucleosides
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The nitrenium ions 3a,b derived from hydrolysis of N-(sulfonatooxy)-N-acetyl-4-aminobiphenyl (1a) and N-(4-biphenylyl)-O-pivaloylhydroxylamine (1b) are trapped by the purine nucleosides 2'-deoxyguanosine (dG), guanosine (G), 8-methylguanosine (8-MeG), adenosine (A), inosine (I), and xanthosine (X) with varying degrees of efficiency. Those nucleosides with a basic N-7 (pK(a)(N7-H+) ≤ 2.3) react with 3a,b with an apparently diffusion-limited rate constant at 20°C of ca. 2.0 x 109 M-1 s-1, determined from the experimental trapping ratios k(nuc)/k(s) and known values of k(s) for the two nitrenium ions. All nucleosides with a basic N-7, including 8-MeG, generate only C-8 adducts upon reaction with 3a,b. The reactions of 8-MeG with 3a,b produce metastable adducts, tentatively identified as 16a,b, that decompose over time into the stable 7,8-dihydroguanosine derivatives 8a,b. Our data, and those of other workers, are consistent with a mechanism that involves initial attack of N-7 on the nitrogen of the nitrenium ions followed by a 1,2 migration and deprotonation (Scheme 2b) to yield the final C-8 adducts. Nucleosides with a less basic N-7 react more slowly with the nitrenium ions and also produce adducts other than C-8 adducts. Inosine generates both the C-8 adducts 6a,b and the O-6 adducts 7a,b. Adenosine reacts with 3a,b to produce the unique azabicyclo[4.1.0]hepta-2,4-diene derivatives 11a,b. plots of log k(nuc) vs pK(a)(N7-H+) show that the β(nuc) for C-8 adduct formation is at least 0.7 for purine nucleosides with pK(a) ≤ 2.3. The purine and pyrimidine selectivity data conclusively demonstrate that the high abundance of C-8 dG adducts observed in DNA from in vivo or in vitro experiments is a consequence of the high selectivity of nitrenium ions for N-7 of dG. Other minor DNA adducts may be produced as a result of structure-dependent modification of site selectivity.
- Kennedy, Sonya A.,Novak, Michael,Kolb, Brent A.
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p. 7654 - 7664
(2007/10/03)
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- Acid-base properties of arylnitrenium ions
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This study uses a combination of laser flash photolysis (LFP) and product analysis to show that singlet nitrenes from the irradiation of phenyl, 4-biphenylyl, and 2-fluorenyl azide can be trapped by protonation in aqueous solutions forming nitrenium ions. With phenyl azide, the phenylnitrenium ion is indicated by the formation of ring-substituted anilines in yields of up to 50% in 1 M acids. The acidity dependence furnishes the ratio k(H):k(exp) = 1.1, where k(H) refers to H+-trapping of singlet phenylnitrene and k(exp) to ring expansion of this species. With k(H) expected to be 2-4 x 1010 M-1 s-1, k(exp) is therefore estimated as 2-4 x 1010 s-1. Protonation by solvent water also occurs, but even though the rate constant is of the order of 109 s-1, it constitutes a minor pathway in competition with the ring expansion. LFP studies in acids reveal a transient that is assigned the structure of N-protonated 4-hydroxy-2,5-cyclohexadienone imine, the intermediate formed by water addition to the para position of the phenylnitrenium ion. With 4-biphenylyl- and 2-fluorenylnitrene, ring expansion (and intersystem crossing) occurs more slowly and protonation by water is faster, with the consequence that there are substantial yields of nitrenium ion without added acids. These nitrenium ions are detected with ns LFP, and their formation from singlet nitrene is observed with ps LFP. Combining the LFP experiments with product analysis furnishes a pK(a) value of 16 for the 4-biphenylylnitrenium ion deprotonating to singlet nitrene in 20% acetonitrile. Thus singlet 4-biphenylylnitrene falls close to the category of a strong base in this solution. LFP experiments in acids show behavior consistent with N-protonation of the nitrenium ion forming an aniline dication. Kinetic analyses furnish pK(a) values of 0.1 (4-aminobiphenyl dication) and 0.6 (2-aminofluorene dication) in 20% acetonitrile with 1 M ionic strength. This and other pieces of evidence are consistent with these arylnitrenium ions being better regarded as 6-iminocyclohexadienyl carbocations. Overall, arylnitrenium ions (ArNH+) are very weak acids in water in their deprotonation to singlet nitrenes. They are also weak bases, accepting a proton to form the aniline dication - 1ArN ? 1ArNH+ ? (ArNH2)2+.
- McClelland, Robert A.,Kahley, Mary Jo,Davidse, P. Adriaan,Hadzialic, Gordana
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p. 4794 - 4803
(2007/10/03)
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- The Electrochemical Preparation and Kinetic and Product Studies of Acylated Quinol and Quinol Ether Imines. In Search of the Hydrolysis Products of the "Ultimate" Carcinogen of N-Acetyl-2-aminofluorene
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The N-acetyl and benzoyl derivatives of 4-methoxy-4-phenyl-2,5-cyclohexadienone imine and the N-benzoyl derivative of 4-hydroxy-4-phenyl-2,5-cyclohexadienone imine (1a-c) have been prepared via anodic oxidation of the corresponding amide of 4-aminobiphenyl in either methanol or water/ acetonitrile, respectively.The products and the kinetics of the acidic and basic hydrolyses of these compounds were studied and the results compared with other N-acylquinol imine derivatives, including N-acetyl-4-hydroxy-4-phenyl-2,5-cyclohexadienone imine (1d), generated by solvolytic routes.The chemistry of these compounds was dependent upon the pH and the substituents on the quinol imine derivative.The major reaction pathways were hydrolysis of the imine linkage to afford the respective dienone and phenyl migration to afford the amides of 2-hydroxy- or 2-methoxy-5-aminobiphenyl.The reactivity of the quinol imine derivatives follows the order: 4-hydroxyl more reactive than 4-methoxyl compounds and N-acetyl more reactive than N-benzoyl derivatives.The higher reactivity for the former compounds is attributed to the greater electron-donating ability of the 4-hydroxyl versus the 4-methoxyl group.The higher reactivity of the N-acetyl relative to the N-benzoyl derivatives is attributed to the ca. 30-fold increase in basicity of the N-acetyl functionality.The additive effect of the 4-hydroxyl and N-acetyl functionality on the basic quinol imine moiety makes compounds having both of the groups difficult to isolate in aqueous media.This serves as a limitation for the preparation of the quinol imine derivative of N-acetyl-2-aminofluorene via the anodic oxidation methods reported herein.
- Novak, Michael,Helmick, John S.,Oberlies, Nicholas,Rangappa, Kanchugarakoppal S.,Clark, William M.,Swenton, John S.
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p. 867 - 878
(2007/10/02)
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- Quinol N-Acyl and Quinol Ether Imines via Anodic Oxidation of Para-Substituted Anilide Derivatives
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Anodic oxidation of N-benzoyl-4-methylaniline in 5percent aqueous methanol in the presence of sodium bicarbonate affords two major products: 4-methoxy-4-methylbenzoquinol N-benzoylimine, 8a, and a dimer, 4--4-methylbenzo
- Swenton, John S.,Biggs, Timothy N.,Clark, William M.
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p. 5607 - 5614
(2007/10/02)
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- Reactivity and selectivity of nitrenium ions derived from ester derivatives of carcinogenic N-(4-biphenylyl)hydroxylamine and the corresponding hydroxamic acid
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N-Acetyl-N-(sulfonatooxy)-4-aminobiphenyl (1a) and N-(4-biphenylyl)-O-pivaloylhydroxylamine (1c) decompose in 5% CH3CN/H2O, μ = 0.5 M, at 20°C via rate-limiting N-O bond heterolysis to generate the nitrenium ion intermediates 2a and 2b, respectively. Addition of Cl- (≤0.5 M) or N3- (≤0.05 M) causes a marked decrease in the yields of all hydrolysis products derived from 1a and 1c, except the rearrangement products 10a and 11, without any change in the hydrolysis rate constants. At 0.5 M Cl- more than 75% of the trappable hydrolysis products of 1a are replaced by the chloro adduct 7a without any observable change in the hydrolysis rate constant, and at 0.025 M N3- 96% of the trappable hydrolysis products of 1a are replaced by the azide adduct 8a, again, without an observable change in the hydrolysis rate constant. Similar results are obtained for 1c. The nucleophile/solvent selectivity ratios, kcl/ks and kaz/ks, are 7.4 ± 0.3 M-1 and (1.02 ± 0.04) × 103 M-1, respectively, for 2a. For 2b k/cl/ks is 15.7 ± 0.8 M-1 and kaz/ks is (2.9 ± 0.2) × 103 M-1. If kaz is at the diffusion controlled limit of 5 × 109 M-1 s-1, ks for 2a is 4.9 × 106 s-1, and ks for 2b is 1.7 × 106 s-1. Both of these ions are considerably less labile to solvent attack than 1-phenylethyl or cumyl carbocations with a 4-phenyl substituent. Surprisingly, 2a and 2b differ in their reactivity to solvent by only a factor of 3, while the estimated rate constants for their generation from starting materials with identical leaving groups differ by a factor of 106. This phenomenon is similar to the situation previously observed by Richard for 1-aryl2,2,2-trifluoroethyl and 1-arylethyl carbocations and may be due to similar factors. A detailed mechanism for the hydrolysis of 1a and 1c, which is consistent with all available experimental data, is presented. The implications of these results for the mechanisms of chemical carcinogenesis by N-arylhydroxylamine derivatives are discussed.
- Novak, Michael,Kahley, Mary Jo,Eiger, Emily,Helmick, John S.,Peters, Hope E.
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p. 9453 - 9460
(2007/10/02)
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- The Addition of Organolithium Reagents to Quinone Silyl Methyl Monoketals. A Useful Expedient in the Synthesis of p-Quinols Having Acid-Sensitive Groups
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Acid hydrolyses of dimethyl ketals 4-alkyl- and 4-aryl-4-hydroxy-2,5-cyclohexadienones having an acid-sensitive functionality often afford low or no yields of the respective 4-substituted 4-hydroxy-2,5-cyclohexadienones (p-quinols).However, addition of me
- Stern, Alan J.,Swenton, John S.
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p. 2465 - 2468
(2007/10/02)
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- Structural and Solvent/Electrolyte Effects on the Selectivity and Efficiency of the Anodic Oxidation of Para-Substituted Aromatic Ethers. An Efficient Route to Quinol Ether Ketals and Quinol Ethers
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The anodic oxidations of the methyl ethers of p-arylphenols C6H4, o-C6H4, o-HO2CC6H4>, the 2-hydroxyethyl ethers of p-arylphenols , and the 2-hydroxyethyl ethers of p-alkylphenols and 4-methyl-1-naphthol were studied.The p-aryl aromatic ethers underwent anodic oxidation in good yield to give the corresponding p-quinol ether ketals.The ratio of nuclear to side-chain products from anodic oxidation of p-alkylanisole derivatives is dependent upon the electrolysis conditions.The 2-hydroxyethyl ether derivatives of p-alkylphenols markedly favor the formation of nuclear oxidation products - providing a useful route to the corresponding p-quinol ether ketals.In addition, methanolic potassium fluoride improves the efficiency of these anodic oxidation processes by about 400percent relative to methanolic potassium hydroxide.These reactions were performed at a constant current (1.0-2.0 A) in a single cell and serve as preparative routes to p-quinol ether ketals and quinol ethers via acid hydrolysis.
- Capparelli, Michael P.,DeSchepper, Richard E.,Swenton, John S.
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p. 4953 - 4961
(2007/10/02)
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- REACTIONS OF ORGANOLITHIUM REAGENTS WITH p-BENZOQUINONES AND CYCLOHEXADIENONS, SYNTHESIS OF 4-ALKYL-4-HYDROXYCYCLOHEXA-2,5-DIEN-1-ONES AND 1,4-DIALKYLCYCLOHEXA-2,5-DIENE-1,4-DIOLS.
-
Addition of organolithium reagents to p-benzoquinones in ether gives the corresponding 4-alkyl-4-hydroxycyclohexa-2,5-dien-1-ones.Addition of excess of the reagent to the p-benzoquinones, or to the 4-alkyl-4-hydroxycyclohexa-3,5-dien-1-ones, in tetrahydrofuran, gives the corresponding dialkylcyclohexa-2,5-diene-1,4-diols.
- Fischer, A.,Henderson, N.
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p. 701 - 704
(2007/10/02)
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