26374-14-1Relevant articles and documents
Picosecond Dynamics of the Photoreduction of Benzophenone by Triethylamine
Shaefer, C.G.,Peters, K.S.
, p. 7566 - 7567 (1980)
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Probing the compound I-like reactivity of a bare high-valent oxo iron porphyrin complex: The oxidation of tertiary amines
Chiavarino, Barbara,Cipollini, Romano,Crestoni, Maria Elisa,Fornarini, Simonetta,Lanucara, Francesco,Lapi, Andrea
, p. 3208 - 3217 (2008/09/20)
The mechanisms of oxidative N-dealkylation of amines by heme enzymes including peroxidases and cytochromes P450 and by functional models for the active Compound I species have long been studied. A debated issue has concerned in particular the character of the primary step initiating the oxidation sequence, either a hydrogen atom transfer (HAT) or an electron transfer (ET) event, facing problems such as the possible contribution of multiple oxidants and complex environmental effects. In the present study, an oxo iron(IV) porphyrin radical cation intermediate 1, [(TPFPP)?+Fe IV=O]+ (TPFPP = meso-tetrakis (pentafluorophenyl) porphinato dianion), functional model of Compound I, has been produced as a bare species. The gas-phase reaction with amines (A) studied by ESI-FT-ICR mass spectrometry has revealed for the first time the elementary steps and the ionic intermediates involved in the oxidative activation. Ionic products are formed involving ET (A?+, the amine radical cation), formal hydride transfer (HT) from the amine ([A(-H)]+, an iminium ion), and oxygen atom transfer (OAT) to the amine (A(O), likely a carbinolamine product), whereas an ionic product involving a net initial HAT event is never observed. The reaction appears to be initiated by an ET event for the majority of the tested amines which included tertiary aliphatic and aromatic amines as well as a cyclic and a secondary amine. For a series of N,N-dimethylanilines the reaction efficiency for the ET activated pathways was found to correlate with the ionization energy of the amine. A stepwise pathway accounts for the C-H bond activation resulting in the formal HT product, namely a primary ET process forming A?+, which is deprotonated at the α-C-H bond forming an N-methyl-N-arylaminomethyl radical, A(-H)?, readily oxidized to the iminium ion, [A(-H)]+. The kinetic isotope effect (KIE) for proton transfer (PT) increases as the acidity of the amine radical cation increases and the PT reaction to the base, the ferryl group of (TPFPP)FeIV=O, approaches thermoneutrality. The ET reaction displayed by 1 with gaseous N,N-dimethylaniline finds a counterpart in the ET reactivity of FeO+, reportedly a potent oxidant in the gas phase, and with the barrierless ET process for a model (P)?+FeIV=O species (where P is the porphine dianion) as found by theoretical calculations. Finally, the remarkable OAT reactivity of 1 with C6F 5N(CH3)2 may hint to a mechanism along a route of diverse spin multiplicity.
Absolute rate constants for the Reactions of tert-Butoxyl, tert-Butylperoxyl, and Benzophenone Triplet with Amines: The Importance of a Stereoelectronic Effect
Griller, D.,Howard, J. A.,Marriott, P. R.,Scaiano, J. C.
, p. 619 - 623 (2007/10/02)
Absolute rate constants have been determined for the reactions of tert-butoxyl, tert-butylperoxyl, and benzophenone triplet with a variety of amines.All three reagents abstract hydrogen from the carbon α to nitrogen with rate constants which are much greater than those for the corresponding reactions with hydrocarbons and isostructural ethers.This rate enhancement is attributed to polar effects on the transition state and to the stabilization of α-aminoalkyls.These product radicals are stabilized by conjugation between the unpaired electron and the nitrogen lone pair, and, as a result, the hydrogen abstractions show a pronounced stereoelectronic effect with abstraction being most facile when the C-H bond being broken is eclipsed with the axis of the nitrogen lone-pair orbital.
