- Benzylic C-H trifluoromethylation of phenol derivatives
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Phenol derivatives were trifluoromethylated using copper/Togni reagent. In dimethylformamide, the benzylic C-H bond at the para position of the hydroxyl group was selectively substituted with a CF3 group. In contrast, aromatic C-H trifluorometh
- Egami, Hiromichi,Ide, Takafumi,Kawato, Yuji,Hamashima, Yoshitaka
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p. 16675 - 16678
(2015/11/25)
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- Mono(aryloxido)titanium(IV) Complexes and their application in the selective dimerization of ethylene
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We report on the synthesis of mono(aryloxido)titanium(IV) complexes of general formula [Ti[O(o-R)Ar]X3), with X = OiPr, ArO = 2-ie.rr-but:yl-4-methylphenoxy and. R = CMe3 (2a), CMe2Ph (2b) and CH2NMe2 (2c). Attempts to reach pure mono(aryloxido) complexes when R = CH2NMe(CH2Ph) (2d) or CH2N(CH2Ph)2 (2e) were unsuccessful, When R = CH2OMe, the analogous mononuclear complex was not obtained, and instead, a dinuclear complex [(2-ieri-butyl-4methyl-6- methoxymethylphenoxy) TiCl(OiPr)(H2-OiPr)2TiCl(OiPr) 2] (3) was formed. Complexes 2b and 3 were characterized by single-crystal X-ray diffraction, The former contains a tetrahedrally coordinated. TiIV centre, whereas in the latter the aryloxido ligand behaves as a chelating-bridging ligand between the two, chemically very different metal centres that form two face-sharing octahedra, Different synthetic approaches starting from. [Ti(OiPr)4] or [TiCl(OiPr) 3] were evaluated and are discussed, The hemllabile behaviour of the aryloxido ligand. resulting from, reversible coordination of its side arm was studied by variable-temperature 1H NMR spectroscopy for 2c (R = CH 2NMe2). Complexes 2a-d were contacted, with ethylene and AlEt3 as cocatalyst, When activated with AlEt3 (3 equiv.) at 20 bar and 60 ° C, complex 2c exhibits interesting activity (2100 g/gTi/h) for the selective dimerization of ethylene to 1-butene (92% C 4"=; 99+% C4=1), Noticeable differences in catalyst activity were observed when the R group was modified,
- Cazaux, Jean-Benoit,Braunstein, Pierre,Magna, Lionel,Saussine, Lucien,Olivier-Bourbigou, Helene
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experimental part
p. 2942 - 2950
(2011/05/13)
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- REACTIVITY OF DIALKYLPHENOLS IN REACTION WITH ACETALS
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In reaction with 2,4-dialkylphenols under the conditions of acid catalysis formaldehyde dialkyl acetals give high yields of the corresponding substituted methylenediphenols.The reaction can be used for the synthesis of compounds which are effective antioxidants.
- Starikova, O. F.,Gurvich, Ya. A.,Styskin, E. L.,Kumok, S. T.
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p. 553 - 555
(2007/10/02)
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- Kinetic Studies of the Methanolysis Reaction of Chloromethylated Phenols
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The solvolysis of 25 differently substituted chloromethylated phenols was studied kinetically in methanol at 25 deg C.A sharp decrease of the initial reaction rate with increasing concentrations of added acids can be explained by a very fast solvolysis of the phenolate anions in comparison with the undissociated compounds.The latter show strictly first order kinetics up to high conversions and the rate constants can be partly correlated with the Jaffe relation.Highly negative values for the reaction constants ρ=-5.4 and ρ=-6.2 for ortho- and para-chloromethylated compounds show, that the undissociated phenols react according to the SN1-mechanism.However, deviations are found for compounds with strongly electron attracting substituents, which may be partly caused by an intramolecular catalytic effect of the phenolic hydroxy group in the case of the ortho-isomers. - Keywords: Methanolysis, Chloromethylated Phenols, Anchimeric Assistance
- Stein, Guenter,Boehmer, Volker,Lotz, Werner,Kaemmerer, Hermann
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p. 231 - 241
(2007/10/02)
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