- Palladium-catalyzed ortho-C-H hydroxylation of benzoic acids
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A simple Pd(OAc)2 catalyzed ortho-hydroxylation of benzoic acids using TBHP as the sole oxidant has been explored. This protocol features relatively broad substrate scope and operational simplicity. The compatibility of ortho-substituted substrates is an effective complement to the previous ortho-hydroxylation reaction.
- Luo, Feihua,He, Shuhua,Gou, Quan,Chen, Jinyang,Zhang, mingzhong
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- Micellar effects upon the rate of alkaline hydrolysis of triflusal
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The rate of hydrolysis for triflusal was measured at varying concentrations of NaOH at four different temperatures (i.e. 25, 35, 45 and 55 °C). The micelles of cetyltrimethylammonium bromide (CTABr), cetyltrimethylammonium chloride (CTACl), cetyltrimethylammonium hydroxide (CTAOH) and dodecyltrimethyl-ammonium bromide (DTABr) had catalytic effect on the rate of hydrolysis. CTABr, CTACl and DTABr gave maxima like curve for the rate-[surfactant] plot while CTAOH gave plateau like curve. The anionic sodium dodecyl sulfate (SDS) did not influence the rate of alkaline hydrolysis of triflusal. The non-ionic Brij-35 inhibited the rate of the hydrolytic reaction. The catalytic effect by cationic micelles was treated by applying the pseudophase ion exchange model while the inhibitive effect by non-ionic micelles has been described by using the Poisson-Boltzmann pseudophase model. The variation in kψ with the change in [surfactant] was used to determined various kinetic parameters e.g., binding constant (Ks), and micellar rate constant (km). The addition of electrolytes decreased the reaction rate in CTABr and CTAOH micelles.
- Al-Lohedan, Hamad A.,Al-Blewi, Fawziah F.,Rafiquee,Issa, Zuheir A.
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p. 321 - 327
(2015/03/18)
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- PD(II)-CATALYZED HYDROXYLATION OF ARENES WITH O2 OR AIR
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Pd (II) -catalyzed ortho-hydroxylat ion of variously substituted aromatic carboxylic acids under O2 or air is achieved under non-acidic conditions. Extensive labeling studies support a direct oxygenation of aryl C-H bonds with molecular oxygen.
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Page/Page column 14; 19-20
(2011/04/24)
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- Electrochemical behavior of triflusal, aspirin and their metabolites at glassy carbon and boron doped diamond electrodes
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The electrochemical behavior of triflusal (TRF) and aspirin (ASA), before and after hydrolysis in water and in alkaline medium using two different electrode surfaces, glassy carbon and boron doped diamond, was studied by differential pulse voltammetry over a wide pH range. The hydrolysis products were 2-(hydroxyl)-4-(trifluoromethyl)-benzoic acid (HTB) for triflusal and salicylic acid (SA) for aspirin, which in vivo represent their main metabolites. The hydrolysis processes were also followed by spectrophotometry. The UV results showed complete hydrolysis after one hour for TRF and after two hours for ASA in alkaline solution. The glassy carbon electrode enables only indirect determination of TRF and ASA through the electrochemical detection of their hydrolysis products HTB and SA, respectively. The oxidation processes of HTB and SA are pH dependent and involve different numbers of electrons and protons. Moreover, the difference between the oxidation peak potential of SA and HTB was equal to 100 mV in the studied pH range from 1 to 8 due to the CF3 of the aromatic ring of HTB molecule. Due to its wider oxidation potential range, the boron doped diamond electrode was used to study the direct oxidation of TRF and ASA, as well as of their respective metabolites HTB and SA.
- Enache, Teodor Adrian,Fatibello-Filho, Orlando,Oliveira-Brett, Ana Maria
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body text
p. 569 - 577
(2010/12/25)
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- Pd(II)-catalyzed hydroxylation of arenes with 1 atm of O2 or air
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(Chemical Equation Presented) Pd(II)-catalyzed ortho-hydroxylation of variously substituted benzoic acids under 1 atm of O2 or air is achieved under nonacidic conditions. Extensive labeling studies support a direct oxygenation of aryl C-H bonds with molecular oxygen.
- Zhang, Yang-Hui,Yu, Jin-Quan
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supporting information; experimental part
p. 14654 - 14655
(2010/01/06)
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- Fluorophenols and (trifluoromethyl)phenols as substrates of site-selective metalation reactions: To protect or not to protect
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O-Methoxymethyl (MOM) protected fluorophenols can be cleanly metalated and subsequently be submitted to site-selective electrophilic substitution. The 2- and 4-isomers exhibit ambivalent reactivity: deprotonation occurs at the position adjacent to the oxygen when butyllithium is employed whereas the position adjacent to the fluorine is attacked by the superbasic mixture of butyllithium and potassium tert-butoxide (LIC-KOR). The MOM-protected (trifluoromethyl)-phenols react exclusively at oxygen-neighboring positions. The meta isomer provides another example of optional site selectivity, undergoing hydrogen/metal exchange at the 2-position with the LIC-KOR reagent and at the 6-position with sec-butyllithium. Unprotected (trifluoromethyl)phenols can also be ortho-metalated after O-deprotonation, although the products are formed in only moderate yields.
- Marzi, Elena,Mongin, Florence,Spitaleri, Andrea,Schlosser, Manfred
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p. 2911 - 2915
(2007/10/03)
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