88889-02-5Relevant articles and documents
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.
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...
