- Condensed ring compd.
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A condensed ring compound capable of becoming an intermediate product suitable for isoxazolines is represented by formula (I). In formula (I), X" represents a halogen atom or the like; n represents any one of integers 0 to 5; X' represents a halogen atom
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Paragraph 0338
(2016/10/08)
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- Synthesis of trifluoromethyl ketones by palladium-catalyzed cross-coupling reaction of phenyl trifluoroacetate with organoboron compounds
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Cross-coupling reaction of aryl trifluoroacetates with organoboron compounds catalyzed by palladium complexes gives trifluoromethyl ketones in moderate to excellent yields under mild conditions. The catalytic process has been designed on the basis of fundamental studies dealing with oxidative addition of phenyl trifluoroacetate to a Pd(0) complex to give a (phenoxo)(trifluoroacetyl)palladium(II) complex and its subsequent reaction with phenylboronic acid to liberate phenyl trifluoromethyl ketone. The catalytic cycle is proposed to be composed of (a) oxidative addition of the ester to give acyl(aryloxo)palladium intermediate, (b) the subsequent transmetallation with arylboron compounds, and (c) reductive elimination. Palladium(0) complexes, as well as catalysts prepared in situ from palladium acetate and 3 molar amounts of tributylphosphine or phosphite at room temperature, serve as convenient and effective catalysts. The process is applicable to a wide range of phenyl- and naphthylboronic acids to give various aryl trifluoromethyl ketones under mild conditions. Aryl perfluoroalkyl ketone derivatives can be similarly prepared in high yields from various phenyl perfluoroalkanecarboxylates and arylboronic acids.
- Kakino,Shimizu,Yamamoto
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p. 371 - 376
(2007/10/03)
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- MECHANISMS OF FREE-RADICAL REACTIONS. XIII. MECHANISM AND SELECTIVITY OF THE FREE-RADICAL HALOGENATION OF ALKYL AROMATIC HYDROCARBONS WITH FLUOROALKYL SUBSTITUENTS
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The free-radical chlorination and bromination of 1-fluoro-2-arylethanes and 1,1,1-trifluoro-2-arylethanes was studied by the method of competing reactions.In all cases a good correalation between log krel and the Brown ?+ constants was observed.The variation of the selectivity in the transition from one reaction series to the other indicates that two independent factors which determine the reactivity (the change in the dissociation energy of the C-H bond and the polar effect of the substituents) have a simultaneous effect.
- Dneprovskii, A. S.,Eliseenkov, E. V.,Mil'tsov, S. A.
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p. 317 - 324
(2007/10/02)
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- Reduction by a Model of NAD(P)H. 29. Kinetics and Isotope Effects for the Reduction of Substituted Trifluoroacetophenone
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Kinetics for the reduction of substituted and unsubstituted α,α,α-trifluoroacetophenone by a model of NAD(P)H in acetonitrile in the presence and absence of a magenesium ion, a catalyst, has been studied.The catalyzed and uncatalyzed reactions show linear free-energy relationships.It is found that the magnesium ion retards the reaction of ceratain substituted trifluoroacetophenones.The kinetic isotope effect and the isotopic ratio in the product are also studied.These values vary depending on the substituent and on the presence or absence of the magnesium ion.The result indicates that there is at least one intermediate in the reaction and is discussed in relation to the stability of the intermediate as well as that of the transition states.
- Ohno, Atsuyoshi,Yamamoto, Hiroyuki,Oka, Shinzaburo
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p. 2041 - 2045
(2007/10/02)
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- Charge-Transfer Quenching of Triplet α-Trifluoroacetophenones
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The effects of ring substituents and of aromatic quenchers on the photoreduction by toluene of α,α,α-trifluoroacetophenone (AF3) have been measured.A plot of log kCT vs. ionization potential of the donor indicates that ΔGCT equals 22percent ΔG for the full electron transfer.A corresponding plot of log kCT vs. the triplet state reduction potential of ring-substituted AF3's, if analyzed as linear, would indicate that there is no intrinsic difference in reactivity between n,?* and ?,?* triplets but would also indicate that ΔGCT equals 42percent ΔG.The discrepancy between the 22 and 42percent is suggested to involve differing reactivities of n,?* and ?,?* triplets.If n,?* triplets are substantially more reactive, the plot vs. triplet reduction potential is expected to curve upward as the equilibrium population of n,?* triplet increases with substitution.
- Wagner, Peter J.,Lam, Henry M. H.
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p. 4167 - 4172
(2007/10/02)
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