- 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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- 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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- N-Alkylation of Imides with O-Alkylisourea under Neutral Conditions
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N-Alkylation of imides with O-alkylisoureas has been found to accur under neutral conditions.Stereochemical data and structural factors indicate that an SN2 mechanism is operative.
- Inoue, Yoshio,Taguchi, Masaaki,Hashimoto, Harukichi
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p. 332 - 334
(2007/10/02)
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