97860-72-5Relevant academic research and scientific papers
Isotope effect profiles in the N-demethylation of N,N-dimethylanilines: A key to determine the pKa of nonheme Fe(III)-OH complexes
Barbieri, Alessia,De Gennaro, Martina,Di Stefano, Stefano,Lanzalunga, Osvaldo,Lapi, Andrea,Mazzonna, Marco,Olivo, Giorgio,Ticconi, Barbara
supporting information, p. 5032 - 5035 (2015/03/30)
N-demethylation of N,N-dimethylanilines promoted by [(N4Py)FeIVO]2+ occurs by an electron transfer-proton transfer (ET-PT) mechanism with a rate determining PT step. From the bell-shaped curve of the KDIE profile it has been estimated that the pKa of [(N4Py)FeIII-OH]2+ is 9.7.
Mechanistic investigation of oxidative Mannich reaction with tert-butyl hydroperoxide. the role of transition metal salt
Ratnikov, Maxim O.,Doyle, Michael P.
supporting information, p. 1549 - 1557 (2013/03/14)
A general mechanism is proposed for transition metal-catalyzed oxidative Mannich reactions of N,N-dialkylanilines with tert-butyl hydroperoxide (TBHP) as the oxidant. The mechanism consists of a rate-determining single electron transfer (SET) that is uniform from 4-methoxy- to 4-cyano-N,N-dimethylanilines. The tert-butylperoxy radical is the major oxidant in the rate-determining SET step that is followed by competing backward SET and irreversible heterolytic cleavage of the carbon-hydrogen bond at the α-position to nitrogen. A second SET completes the conversion of N,N-dimethylaniline to an iminium ion that is subsequently trapped by the nucleophilic solvent or the oxidant prior to formation of the Mannich adduct. The general role of Rh2(cap) 4, RuCl2(PPh3)3, CuBr, FeCl 3, and Co(OAc)2 in N,N-dialkylaniline oxidations by T-HYDRO is to initiate the conversion of TBHP to tert-butylperoxy radicals. A second pathway, involving O2 as the oxidant, exists for copper, iron, and cobalt salts. Results from linear free-energy relationship (LFER) analyses, kinetic and product isotope effects (KIE and PIE), and radical trap experiments of N,N-dimethylaniline oxidation by T-HYDRO in the presence of transition metal catalysts are discussed. Kinetic studies of the oxidative Mannich reaction in methanol and toluene are also reported.
N-Demethylation of N,N-Dimethylanilines by the benzotriazole N-Oxyl radical: Evidence for a two-step electron transfer-proton transfer mechanism
Baciocchi, Enrico,Bietti, Massimo,Lanzalunga, Osvaldo,Lapi, Andrea,Raponi, Daniele
supporting information; experimental part, p. 1378 - 1385 (2010/06/11)
"Chemical Equation Presented" The reaction of the benzotriazole N-oxyl radical (BTNO) with a series of 4-X-N,N-dimethylanilines (X = CN, CF 3, CO2CH2CH3, CH3, OC6H5, OCH3) has been investigated in CH 3CN. Product analysis shows that the radical, 4-X-C6H 4N(CH3)CH2·, is first formed, which can lead to the N-demethylated product or the product of coupling with BTNO. Reaction rates were found to increase significantly by increasing the electron-donating power of the aryl substituents (p+ = -3.8). With electron-donating substituents (X = CH3, OC6H5, OCH3), no intermolecular deuterium kinetic isotope effect (DKIE) and a substantial intramolecular DKIE are observed. With electron-withdrawing substituents (X = CN, CF3, CO2CH2CH 3), substantial values of both intermolecular and intramolecular DKIEs are observed. These results can be interpreted on the basis of an electron-transfer mechanism from the N,N-dimethylanilines to the BTNO radical followed by deprotonation of the anilinium radical cation (ET-PT mechanism). By applying the Marcus equation to the kinetic data for X = CH3, OC 6H5, OCH3 (rate-determining ET), a reorganization energy for the ET reaction was determined (λ BTNO/DMA= 32.1 kcal mol- 1). From the self-exchange reorganization energy for the BTNO/BTNO- couple, a self-exchange reorganization energy value of 31.9 kcal mol-1 was calculated for the DMA·+/DMA couple.
Anilinic N-oxides support cytochrome P450-mediated N-dealkylation through hydrogen-atom transfer
Roberts, Kenneth M.,Jones, Jeffery P.
experimental part, p. 8096 - 8107 (2010/09/11)
The mechanism of N-dealkylation mediated by cytochrome P450 (P450) has long been studied and argued as either a single electron transfer (SET) or a hydrogen atom transfer (HAT) from the amine to the oxidant of the P450, the reputed iron-oxene. In our study, tertiary anilinic N-oxides were used as oxygen surrogates to directly generate a P450-mediated oxidant that is capable of N-dealkylating the dimethylaniline derived from oxygen donation. These surrogates were employed to probe the generated reactive oxygen species and the subsequent mechanism of N-dealkylation to distinguish between the HAT and SET mechanisms. In addition to the expected N-demethylation of the product aniline, 2,3,4,5,6-pentafluoro-N,N-dimethylaniline N-oxide (PFDMAO) was found to be capable of N-dealkylating both N,N-dimethylaniline (DMA) and N-cyclopropyl-N-methylaniline (CPMA). Rate comparisons of the N-demethylation of DMA supported by PFDMAO show a 27-fold faster rate than when supported by N,N-dimethylaniline N-oxide (DMAO). Whereas intermolecular kinetic isotope effects were masked, intramolecular measurements showed values reflective of those seen previously in DMAO- and the native NADPH/O2-supported systems (2.33 and 2.8 for the N-demethylation of PFDMA and DMA from the PFDMAO system, respectively). PFDMAO-supported N-dealkylation of CPMA led to the ring-intact product N-cyclopropylaniline (CPA), similar to that seen with the native system. The formation of CPA argues against a SET mechanism in favor of a P450-like HAT mechanism. We suggest that the similarity of KIEs, in addition to the formation of the ring-intact CPA, argues for a similar mechanism of Compound I (Cpd I) formation followed by HAT for N-dealkylation by the native and N-oxide-supported systems and demonstrate the ability of the N-oxide-generated oxidant to act as an accurate mimic of the native P450 oxidant.
Electron-transfer mechanism in the N-demethylation of N,N-dimethylanilines by the phthalimide-N-oxyl radical
Baciocchi, Enrico,Bietti, Massimo,Gerini, Maria Francesca,Lanzalunga, Osvaldo
, p. 5144 - 5149 (2007/10/03)
The reactivity of the phthalimide N-oxyl radical (PINO) toward the N-methyl C-H bond of a number of 4-X-substituted N,N-dimethylanilines (X = OMe, OPh, CF3, CO2Et, CN) has been investigated by product and kinetic analysis. PINO was generated in CH3CN by reaction of N-hydroxyphthalimide (NHPI) with Pb(OAc)4 or, for the kinetic study of the most reactive substrates (X = OMe, OPh), with tert-butoxyl radical produced by 266 nm laser flash photolysis of di-tert-butyl peroxide. The reaction was found to lead to the N-demethylation of the N,N-dimethylaniline with a rate very sensitive to the electron donating power of the substituent (ρ+ = -2.5) as well as to the oxidation potential of the substrates. With appropriately deuterated N,N-dimethylanilines the intermolecular and intramolecular deuterium kinetic isotope effects (DKIEs) were measured for some substrates (X = OMe, CO2Et, CN) with the following results. First, intramolecular DKIE [(kH/kD) intra] was found to be always different and higher than intermolecular DKIE [(kH/kD)inter]; second, no intermolecular DKIE [(kH/kD)inter = 1] was observed for X = OMe, whereas substantial values of (kH/k D)inter were exhibited by X = CO2Et (4.8) and X = CN (5.8). These results, while are incompatible with a single step hydrogen atom transfer from the N-C-H bond to the N-oxyl radical, as proposed for the reaction of PINO with benzylic C-H bonds, can be nicely interpreted on the basis of a two-step mechanism involving a reversible electron transfer from the aniline to PINO leading to an anilinium radical cation, followed by a proton-transfer step that produces an α-amino carbon radical. In line with this conclusion the reactivity data exhibited a good fit with the Marcus equation and a λ value of 37.6 kcal mol-1 was calculated for the reorganization energy required in this electron-transfer process. From this value, a quite high reorganization energy (> 60 kcal mol-1) is estimated for the PINO/NHPI(-H)- self-exchange reaction. It is suggested that the N-demethylated product derives from the reaction of the α-amino carbon radical with PINO to form either a cross-coupling product or an α-amino carbocation. Both species may react with the small amounts of H2O present in the medium to form a carbinolamine that, again by hydrolysis, can be eventually converted into the N-demethylated product.
On isotope effects for the cytochrome P-450 oxidation of substituted N,N-dimethylanilines
Dinnocenzo,Karki,Jones
, p. 7111 - 7116 (2007/10/02)
Isotope effects were determined for the oxidative demethylation of the substituted N-methyl-N-(trideuteriomethyl)anilines 1a-d, and the corresponding N,N-bis(dideuteriomethyl)anilines 2a-d, by microsomal cytochrome P-450. The pairs of p-cyano- and p-nitro
Kinetics and Mechanisms of Oxygen Transfer in the Reaction of p-Cyano-N,N-dimethylaniline N-Oxide with Metalloporphyrin Salts. 2. Amine Oxidation and Oxygen Transfer to Hydrocarbon Substrates Accompanying the Reaction of p-Cyano-N,N-dimethylaniline N-Oxide with meso-(Tetraphenylporphi...
Dicken, C. Michael,Lu, Fu-Lung,Nee, Michael W.,Bruice, Thomas C.
, p. 5776 - 5789 (2007/10/02)
The catalysis of the decomposition of p-cyano-N,N-dimethylaniline N-oxide (NO) with meso-(tetraphenylporphinato)iron(III) chloride IIICl> has been studied at 25 deg C in CH2Cl2 with i = 5.0E-4 to 8.0E-3 M > IIICl>i = 3.0E-5 to 5.0E-4 M.The iron(III) porphyrin catalyst was shown to be unaltered in catalytic efficiency to 120 turnovers (the highest examined).The influence of O2 and the purity of solvent upon the kinetics of the reactions and products obtained have been assessed.In the absence of an oxidizable substrate, NO gives way to the following products: p-cyano-N,N-dimethylaniline (DA), 52percent yield; p-cyano-N-methylaniline (MA), 25percent yield; N-formyl-p-cyano-N-methylaniline (FA), 4percent yield; p-cyanoaniline (A), 2percent yield; N,N'-dimethyl-N,N'-bis(p-cyanophenyl)hydrazine (H), 12percent yield; N,N'-bis(p-cyanophenyl-N-methylmethylenediamine (MD), 6percent yield; and CH2O, 11percent yield.The major portion of the products (i.e., DA, MA, H and MD) absorb appreciably at 320 nm where absorbance by (TPP)FeIIICl is minimal.The formation of products was followed spectrophotometrically at 320 nm and by HPLC at 280 and 320 nm.Both means were found to be in quantitative agreement.Spectral monitoring of the increase in A320 showed that the first-order decomposition of the N-oxide was independent of i but increases with an increase in IIICl>i.The appearance of DA, MA, FA, MD, and CH2O also followed the first-order rate law, while the formation of the products H and A are characterized by a lag period followed by a constantly accelerated formation ending abruptly with the consumption of the N-oxide.Of the various products, only A exhibited inhibition of the kinetics for decomposition of N-oxide by (TPP)FeIIICl.At the concentration formed in the kinetic experiment, however, A is not inhibiting.The rate constant for "oxygen" transfer from NO to (TPP)FeIIICl to form IV=O>+. was determined by trapping this species with 2,4,6-tri-tert-butylphenol (TBPH).In the presence of TBPH trap, DA is formed in 100percent yield, showing that the other decomposition products of the N-oxide arise via stepwise oxidation of DA by IV=O>+..An intermolecular deuterium kinetic isotope effect of unity was obtained by comparison of the initial rate contants for the reactions of p-NCC6H4N+(CH3)2O-/p-NCC6H4N+(CD3)2O-.A discriminatory intramolecular deuterium isotope effect of 4.5 was observed when p-NCC6H4N+(CH3)(CD3)O- was used and the formation of p-NCC6H4NH(CD3)/p-NCC6H4NH(CH3) was monitored.The isotope effects are in agreement with the finding that rate-determining oxygen transfer from NO to (TPP)FeIIICl is followed by demethylation of DA.A variety of alkenes and cyclohexane are shown to compete with DA as substrates.With these, the yields of epoxidation and/or hydroxylation products are comparable to those reported previously when iodosylbenzene was used as the oxygen source under similar conditions.The stereospecifity seen with iodosylbenzene is also evidenced with NO.At 1.0 M 2,3-dimeth...
