- Highly Active Dinuclear Titanium(IV) Complexes for the Catalytic Formation of a Carbon-Heteroatom Bond
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A series of mononuclear titanium(IV) complexes with the general composition κ3-[R{NHPh2P(X)}2Ti(NMe2)2] [R = C6H4, X = Se (3b); R = trans-C6H10, X = S (4a), Se (4b)] and [{κ2-N(PPh2Se)2}2Ti(NMe2)2] (6b) and two dinuclear titanium(IV) complexes, [C6H4{(NPh2PS)(N)}Ti(NMe2)]2 (3c) and [{κ2-N(PPh2Se)}Ti(NMe2)2]2 (6c), are reported. Dinuclear titanium(IV) complex 6c acts as an efficient catalyst for the chemoselective addition of an E-H bond (E = N, O, S, P, C) to heterocumulenes under mild conditions. The catalytic addition of aliphatic and aromatic amines, alcohol, thiol, phosphine oxide, and acetylene to the carbodiimides afforded the corresponding hydroelemented products in high yield at mild conditions with a broader substrate scope. The catalytic efficiency of the dinuclear complex depends on the cooperative effect of the TiIV ions, the systematic variation of the intermetallic distance, and the ligand's steric properties of the complex, which enhances the reaction rate. Most interestingly, this is the first example of catalytic insertion of various E-H bonds into the carbodiimides using a single-site catalyst because only the titanium-mediated insertion of E-H into a C-N unsaturated bond is reported to date. The amine and alcohol insertion reaction with the carbodiimides showed first-order kinetics with respect to the titanium(IV) catalyst as well as substrates. A most plausible mechanism for hydroelementation reaction is also proposed, based on the spectroscopic data of the controlled reaction, a time-course study, and the Hammett plot.
- Bhattacharjee, Jayeeta,Harinath, Adimulam,Banerjee, Indrani,Nayek, Hari Pada,Panda, Tarun K.
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supporting information
p. 12610 - 12623
(2018/10/09)
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- Synthetic method for isourea catalyzed by rare-earth compound
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The invention relates to a synthetic method for isourea catalyzed by a rare-earth compound. The synthetic method comprises the following steps: (1) enabling carbodiimide which is as shown in a formula (1) and alcohol which is as shown in a formula (2) to react at 25 to 60 DEG C under the catalytic action of rare earth amine to obtain the isourea, wherein the structural formulae of the formula (1) and the formula (2) are as shown in the description, wherein R1 and R2 are independently selected from C3-C8 alkyls or aryls; R3 is C1-C3 alkyls or substituted benzyls, wherein the substituted benzyls are the benzyls which contain a methyl, a naphthyl, a halogen or a pyridine ring; the rare earth amine is one of lanthanum tris[N,N-bis(trimethylsilane)amide], neodymium tris[N,N-bis(trimethylsilane)amide], samarium tris[N,N-bis(trimethylsilane)amide] or ytterbium tris[N,N-bis(trimethylsilane)amide]. According to the method, raw materials are easily obtained; the operation is simple and convenient; conditions of an application method are mild; the yield is high; the substrate application range is wide.
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Paragraph 0131-0134
(2018/03/24)
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- A novel synthesis of 2-alkylthiobenzothiazoles and 2-alkylthiobenzoxazoles
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3H-Benzothiazole-2-thione and 3H-benzoxazole-2-thione were selectively S-alkylated by use of O-alkylisoureas as the alkylating reagents. The reactions could be performed under mild reaction conditions in short reaction times, and high yields were obtained using O-primary-alkylisoureas, whereas low yields were obtained with sec-and tert-alkylisoureas.
- Yu, Yanfei,Li, Zhengning,Jiang, Lan
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experimental part
p. 632 - 640
(2012/06/01)
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- Synthesis of fluorosubstituted three ring esters and their dielectric properties
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Laterally substituted by fluorine atoms 4-cyanophenyl 4-(4- pentylbenzoyloxy)-benzoates have been prepared and their phase transition temperatures, enthalpies and dielectric properties upon frequency were evaluated. The novel compounds exhibit a broad range of nematic mesophase, large positive dielectric anisotropy changing sign at low frequency. They are convenient components of LC mixtures for dual frequency addressing devices. Copyright Taylor & Francis Group, LLC.
- Ziobro, Dorota,Dziaduszek, Jerzy,Filipowicz, Marek,Dabrowski, Roman,Czu, Joanna,Urban, Stanislaw
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experimental part
p. 258 - 271
(2012/08/08)
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- Regiospecific 4-O-alkylation of tetronic acids with isoureas
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4-Alkoxy-5H-furan-2-ones (4-O-alkyl tetronates) with various types of substituents at positions C-3, C-5, or C-3 and C-5 were prepared in good yields and under mild conditions from the corresponding parent tetronic acids and readily available isoureas of the respective primary or secondary alcohols. 2-O-Alkylation was not observed in any case. 4-Alkoxycoumarins are accessible likewise.
- Schobert, Rainer,Siegfried, Sven
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p. 686 - 688
(2007/10/03)
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- One pot conversion of alcohols to disulfides mediated by benzyltriethylammonium tetrathiomolybdate
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A one pot conversion of alcohols to disulfides in good yields via the activation of a hydroxyl group with DCC or P(NMe2)3 / CCl4 followed by treatment with benzyltriethylammonium tetrathiomolybdate is reported.
- Sinha, Surajit,Ilankumaran,Chandrasekaran
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p. 14769 - 14776
(2007/10/03)
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