27557-84-2Relevant articles and documents
Neodymium alkoxides: Synthesis, characterization and their combinations with dialkylmagnesiums as unique systems for polymerization and block copolymerization of ethylene and methyl methacrylate
Gromada, Jerome,Mortreux, Andre,Chenal, Thomas,Ziller, Joseph W.,Leising, Frederic,Carpentier, Jean-Francois
, p. 3773 - 3788 (2002)
The synthesis and characterization (NMR and x-ray) of a variety of neodymium alkoxides derived from simple and functionalized tertiary monoalcohols, and their application as inorganic precursors in combination with dialkylmagnesium reagents for ethylene and methyl methacrylate (MMA) (co)-polymerization have been investigated. Salt metathesis reactions between NdCl3 and sodium alkoxides in THF led to the formation of trinuclear complexes [Nd3(μ3-OR)2(μ2- OR)3(OR)4(thf)2] with R = tBu (1), tAm (2), while aggregate structure [Nd12(OtAm)26(HOtAm)2Cl11Na] ·(OEt2)2 (3) was obtained when the synthesis was performed in Et2O. [Nd3(μ3-OtBu)2(μ2- OtBu)3(OtBu)4(HOtBu)2] (4), prepared by aminolysis of Nd[N(SiMe3)2]3 in hexane, slowly decomposed in toluene into oxo complex [Nd5(μ5-O)(μ3-OtBu)4 (μ2-OtBu)4(OtBu)5] (5). Finally, the dimer [Nd2(μ2,η2-OR)2 (η2-OR)2(η1-OR)2] (OR = OCMe2CH2CH2OMe) (6) was synthesised by aminolysis reaction from the corresponding γ-donor-functionalized alcohol. Some of these neodymium alkoxides, in particular homoleptic complex 1, when associated in situ to one equivalent of a dialkylmagnesium, allow the formation of an active catalyst for ethylene polymerization. Under mild conditions (0°C, 1 bar), the latter catalyst system exhibited a moderate activity (5-10 kgmol-1 h-1 bar-1). Effective transfer reactions were observed in the presence of H2 or PhSiH3 and renewal/improvement of activity occurred upon extra addition of dialkylmagnesium. The most outstanding feature of this catalytic system lies in the precipitation of the active Nd-polyethylenyl species during the ethylene polymerization course as solid S which could be isolated. This heterogeneity was turned to good account, enabling to achieve heterogeneous solid-gas ethylene polymerization and to prepare diblock PE-PMMA copolymers with high diblock efficiency and high molecular weights (Mn > 200 000). A catalytic cycle for this unique system is proposed based on the isolation of a transmetallation product (7) from a neodymium alkoxide/dialkylmagnesium combination and NMR studies of the latter.
Stereoselective Synthesis of Z-α,β-Unsaturated Sulfones Using Peterson Reagents
Ando, Kaori,Wada, Tomohiro,Okumura, Miho,Sumida, Hiroshi
supporting information, p. 6026 - 6029 (2016/01/09)
New Peterson reagents were prepared by introducing alkyloxy groups on the silicon atom in order to fix the conformation of the sulfone anion. The reagents 1d and 1e reacted with a variety of aldehydes after the treatment with Li-base to give Z-α,β-unsaturated sulfones with up to >99:1 selectivity in good to excellent yields. For the reaction with aliphatic aldehydes, CPME (cyclopentyl methyl ether) is the choice of solvent, while DME (1,2-dimethoxyethane) gave higher selectivity for the reaction with aromatic aldehydes.
