599-00-8Relevant articles and documents
The 2-butyl cation in trifluoroacetic acid. A hydrogen-bridged carbonium ion
Dannenberg,Goldberg,Barton,Dill,Weinwurzel,Longas
, p. 7764 - 7768 (1981)
The solvolyses of CH3CH2CH(OTs)CH3, CH3CH2CD(OTs)CD3 (III) and CD3CD2CH(OTs)CH3 (XIII) have been studied in CF3COOH and CF3COOD. The product distributions and solvolysis rates are consistent with the intermediacy of a hydrogen-bridged 2-butyl cation. The ratio of the solvolysis rates of III to XIII is 1.1-1.2 which is consistent with anchimeric assistance by a β-H on C3. The rate of additions of CF3COOH to 2-butene is less than half as fast as the trifluoroacetolysis, thereby eliminating 2-butene as an intermediate in the reaction. The steady-state concentration of 2-butene is shown to be proportional to added [CF3COONa], indicating that the trifluoroacetate anion, often used as a buffer, is a strong enough base to direct the reaction toward elimination products.
Synthesis of 4,8-anhydro-2,3-dideoxy-D-galacto- and -D-gluco-non-3-enose dimetthyl acetal and their use as new probes for determining by 1H-n.m.r. spectroscopy the steric course of protonation by glycoside hydrolases
Fritz, Hans,Lehmann, Jochen,Schmidt-Schuchardt, Markus,Weiser, Wolfgang
, p. 129 - 142 (1991)
The title nonosulose derivatives 2 (D-galacto) and 4 (D-gluco) were prepared by multistep syntheses.Addition of water to the enolic double bonds of both compounds was catalyzed only by the corresponding enzymes β-D-galactosidase from Escherichia coli, α-D-galactosidase from green coffee beans, and β-D-glucosidase from sweet almonds, α-D-glucosidase from yeast.The enzymic hydration of 2, performed in D2O to analyze the steric course of the addition, gave 2,3-dideoxy-α-D-galacto-(3-2H)-nonos-4-ulose dimethyl acetal (5), which when hydrolyzed gave an equilibrium mixture of the spiranes 16 and 17 as the main products (85percent) and the fused-ring systems 18 and 19 as minor components (15percent).Borohydride reduction of the product of enzymic hydration gave a separable mixture of the two epimers 14 and 15, convertible in acidic methanol for 8h at 62 deg C into 20 and 22, respectively.The rigid, bicyclic ring-systems allow facile assignment of the configuration at the monodeuterated C-3 as (S), thereby allowing determination of the steric course of the initial, enzyme-catalyzed step, the deuteration of the enolic double bond in the substrates used.
STUDY OF PROTONATION AND DEUTERIUM EXCHANGE OF CARBAZOLES IN TRIFLUOROACETIC ACID-1,2-DICHLOROETHANE
Sirotkina, E. E.,Moskalev, N. V.,Shabotkin I. G.,Ogorodnikov, V. D.,Khayut, E. B.
, p. 438 - 442 (1985)
The protonation of the aromatic ring of 9-methylcarbazole under the influence of trifluoroacetic acid in 1,2-dichloroethane was established by spectrophotometry.Deuterium exchange between 9-methylcarbazole and deuterotrifluorotrifluoroacetic acid was evaluated quantitatively by means of mass spectrometry and the PMR spectra.Highly deuterated carbazole and 9-methylcarbazole were obtained for the first time.
Regioselective deuterium labeling of estrone and catechol estrogen metabolites
Stack, Douglas E.,Ritonya, Justin,Jakopovic, Scott,Maloley-Lewis, Brittney
, p. 32 - 38 (2015/01/08)
Increased exposure to estrogens and estrogen metabolites is linked with increased rates of breast, ovarian and other human cancers. Metabolism of estrogen can led to formation of electrophilic o-quinones capable of binding to DNA. In order to gain insight into the mechanism of estrogen-induced DNA damage, estrone and catechol estrogens derived from estrone, have been regioselectively labeled with deuterium at the 1-position. Estrone-1-d, estrone-1,2,4-d3, 4-hydroxyestrone-1-d and 2-hydroxyestrone-1-d have been synthesized with or without deuteriums at the 16-position. The key labeling step involves deuterated trifluoroacetic acid exchange catalyzed by t-butyl alcohol. This economical, straightforward labeling technique makes available a range of estrone compounds containing deuterium at the 1-position.
Evidence for the existence of terminal scandium imidos: Mechanistic studies involving imido-scandium bond formation and c-h activation reactions
Wicker, Benjamin F.,Fan, Hongjun,Hickey, Anne K.,Crestani, Marco G.,Scott, Jennifer,Pink, Maren,Mindiola, Daniel J.
, p. 20081 - 20096 (2013/02/23)
The anilide-methyl complex (PNP)Sc(NH[DIPP])(CH3) (1) [PNP - = bis(2-diisopropylphosphino-4-tolyl)amide, DIPP = 2,6-diisopropylphenyl] eliminates methane (kavg = 5.13 × 10-4 M-1s-1 at 50 °C) in the presence of pyridine to generate the transient scandium imido (PNP)Sc=[DIPP](NC 5H5) (A-py), which rapidly activates the C-H bond of pyridine in 1,2-addition fashion to form the stable pyridyl complex (PNP)Sc(NH[DIPP])(η2-NC5H4) (2). Mechanistic studies suggest the C-H activation process to be second order overall: first order in scandium and first order in substrate (pyridine). Pyridine binding precedes elimination of methane, and α-hydrogen abstraction is overall-rate-determining [the kinetic isotope effect (KIE) for 1-d1 conversion to 2 was 5.37(6) at 35 C and 4.9(14) at 50 C] with activation parameters ΔH? = 17.9(9) kcal/mol and ΔS? = -18(3) cal/(mol K), consistent with an associative-type mechanism. No KIE or exchange with the anilide proton was observed when 1-d3 was treated with pyridine or thermolyzed at 35 or 50 °C. The post-rate-determining step, C-H bond activation of pyridine, revealed a primary KIE of 1.1(2) at 35 °C for the intermolecular C-H activation reaction in pyridine versus pyridine-d5. Complex 2 equilibrated back to the imide A-py slowly, as the isotopomer (PNP)Sc(ND[DIPP])(η2-NC5H4) (2-d 1) converted to (PNP)Sc(NH[DIPP])(η2-NC 5H3D) over 9 days at 60 °C. Molecular orbital analysis of A-py suggested that this species possesses a fairly linear scandium imido motif (169.7 ) with a very short Sc-N distance of 1.84 A?. Substituted pyridines can also be activated, with the rates of C-H activation depending on both the steric and electronic properties of the substrate.
NEW METHOD FOR α-DEUTERATION OF CARBOXYLIC ACIDS
Dmitrevskaya, L. I.,Kurkovskaya, L. N.,Ponomarenko, N. K.,Usorov, M. I.,Smushkevich, Yu. I.,Suvorov, N. M.
, p. 1987 - 1989 (2007/10/02)
The action of deuterotrifluoroacetic acid on the mixed anhydrides of alkanoic acids and trifluoroacetic acid, followed by hydrolysis, leads to the formation of α-deuterated alkanoic acids.The kinetics of isotope exchange were studied, and a mechanism was proposed for the α-deuteration of the mixed anhydrides, involving enolization through a cyclic transition state in the slow stage of the reaction.
Non-specific tritiation of some carcinogenic aromatic amines
Breeman,Kaspersen,Westra
, p. 741 - 750,748,749 (2007/10/05)
2-Aminofluorene, 4-amino-3-methylbiphenyl, 4-amino-biphenyl and 4-amino-4'-fluorobiphenyl were tritiated by acid catalyzed exchange of the corresponding nitro compounds followed by catalytic reduction. The exchange reactions were carried out by heating the nitro compounds in [3H]-trifluoroacetic acid with a catalytic amount of trifluoromethanesulphonic acid (TFMS). No loss of tritium could be detected during the conversion of the tritiated nitro compounds into the corresponding amines by catalytic hydrogenation. Incorporation into the ortho position is very low (4%). During the metabolic activation and binding of the tritiated N-acetyl-2-aminofluorene to rat liver DNA in vivo, no tritium exchange occurred.
