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Triflate Complexes (triflate + complex)
Selected AbstractsChemInform Abstract: Chiral Amine,Silyl Triflate Complex Mediated Asymmetric Intramolecular Michael,Aldol Reaction via a Novel Enantioselective Enol Silylation Process.CHEMINFORM, Issue 1 2001Kiyosei Takasu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Enantioselective Friedel,Crafts Alkylations Catalyzed by Bis(oxazolinyl)pyridine,Scandium(III) Triflate Complexes.CHEMINFORM, Issue 50 2007David A. Evans Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Enantioselective Friedel,Crafts Alkylations Catalyzed by Bis(oxazolinyl)pyridine,Scandium(III) Triflate Complexes.CHEMINFORM, Issue 50 2007David A. Evans Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Enantioselective Friedel,Crafts Alkylations of ,,,-Unsaturated 2-Acyl Imidazoles Catalyzed by Bis(oxazolinyl)pyridine,Scandium(III) Triflate Complexes.CHEMINFORM, Issue 44 2005David A. Evans No abstract is available for this article. [source] Synthesis and Reactivity of Oxametallacyclic Niobium Compounds by Using ,,,-Unsaturated Carbonyl Ligands,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2008Rocío A. Arteaga-Müller Abstract Reduction of mono(cyclopentadienyl)niobium complexes [NbCpRCl4] [CpR = C5Me4H (1), C5H4SiMe2Cl (2), C5H4SiMe3 (3)] with Na/Hg in the presence of methyl methacrylate [MMA, CH2=C(Me)C(O)OMe (a)], methyl acrylate [MA, CH2=CHC(O)OMe (b)] and mesityl oxide [MO, CMe2=CHC(O)Me (c)] afforded the corresponding derivatives [NbCpRCl2(LL)] [CpR = C5Me4H, LL = MMA (1a); CpR = C5H4SiMe2Cl, LL = MMA (2a), MA (2b), MO (2c); CpR = C5H4SiMe3, LL = MMA (3a), MA (3b)] in variable yields depending on both the cyclopentadienyl and the ,,,-unsaturated carbonyl compounds. The reactivity of these complexes was studied toward protic and Lewis acids. Addition of triflic acid TfOH (Tf = CF3SO2) to 3b gave the triflate complex [NbCpRCl2{(CH2)2C(O)OMe}(OTf)] [CpR = C5H4SiMe3 (4)]. The Lewis acids E(C6F5)3 (E = B, Al) reacted with complexes 2b and 3b to give the three-membered metallacyclic (or ,2 -enone) compounds [NbCpRCl2{,2 -CH2=CHC(OMe){O·E(C6F5)3}}] [CpR = C5H4SiMe2Cl, E = B (5), Al (6); CpR = C5H4SiMe3, E = B (7), Al (8)], which decomposed to the corresponding adducts MA·E(C6F5)3. The same reaction with the 2a and 3a derivatives only allowed the observation of the corresponding adducts MMA·E(C6F5)3. Complexes 2a,b and 3a,b reacted with CO with elimination of the acrylate compounds, MA and MMA, respectively, to give the carbonylniobium(III) compounds [NbCpRCl2(CO)2]2 [CpR = C5H4SiMe2Cl (9), C5H4SiMe3 (10)]. Analogous reactions with CNAr showed the elimination of the free MA and MMA compounds. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Enantioselective Mukaiyama-Aldol Reaction of Pyruvates and 1-Phenyl- 1-trimethylsilyloxyethene Catalyzed by Lanthanide/Pybox ComplexesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2006Giovanni Desimoni Abstract The enantioselective Mukaiyama-aldol reaction between 1-phenyl-1-trimethylsilyloxyethene (1) and three pyruvates (2a,c) is catalyzed by the lanthanide triflate complexes of(4S,5S)-2,6-bis[5-phenyl-4-(triisopropylsilyloxy)methyl-1,3-oxazolin-2-yl]pyridine (3). The best catalysts are the LuIII - and ScIII -based complexes that give high yields of (S)- 4a,c and enantiomeric excesses up to 99.5,%. The LaIII -based complex favors the formation of the opposite enantiomer [77,% ee of (R)- 4c]. The rationale of the stereochemical outcome is proposed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Tripodands with Phenyl and Thiophenyl Rings and Nitrogen Bridgehead Atoms,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2006Martin Baier Abstract The flexible tripodands 7,9 and 15 with phenyl and thiophenyl rings as "legs" and nitrogen as bridgehead atoms have been synthesized by three-component condensation reactions of the corresponding amine with the aryl halide. The more rigid species 10,14 and 17 were built up from the podands 7,9 as well as from their iodine substitution products 33,35 by a sequence of ethynylation and C,C coupling reactions. Podand 16 was prepared from tris-iodide 36 by Sonogashira coupling with phenylacetylene. In the cases of 7, 12, 15,17, 22, 24, 35, 36, and 41 the structural parameters were determined by X-ray studies. With the exception of 7, 12, and 17, all structures show either close intermolecular contacts between heteroatoms (15, 22, 24, 35, and 36), C,H···N hydrogen bonding (41), or are closely packed as a result of ,···, stacking (16). We were able to isolate silver triflate complexes of 9, 10, and 16, and in the case of 9 we obtained crystals suitable for X-ray diffraction studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Efficient Platinum(II) Catalyzed Hydroformylation Reaction in Water: Unusual Product Distribution in Micellar MediaADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2010Marina Gottardo Abstract The hydroformylation of a variety of terminal and internal alkenes is efficiently performed by cationic platinum triflate complexes of the type [P2Pt(H2O)2](OTf)2 under mild conditions in an aqueous micellar medium. The use of surfactants is essential to ensure dissolution of the catalyst and substrate in water with catalysts being positioned on the anionic surface of the micelles. Aldehydes are obtained with linear to branched ratios up to >99:1. With styrene derivatives also the corresponding benzaldehydes are formed. The catalyst can be separated by extraction of the organic products with hexane and recycled for at least four times with only a modest loss of activity and no effect on selectivity. [source] Efficient Intramolecular Hydroalkoxylation of Unactivated Alkenols Mediated by Recyclable Lanthanide Triflate Ionic Liquids: Scope and MechanismCHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2010Alma Dzudza Dr. Abstract Lanthanide triflate complexes of the type [Ln(OTf)3] (Ln=La, Sm, Nd, Yb, Lu) serve as effective, recyclable catalysts for the rapid intramolecular hydroalkoxylation (HO)/cyclization of primary/secondary and aliphatic/aromatic hydroxyalkenes in imidazolium-based room-temperature ionic liquids (RTILs) to yield the corresponding furan, pyran, spirobicyclic furan, spirobicyclic furan/pyran, benzofuran, and isochroman derivatives. Products are straightforwardly isolated from the catalytic solution, conversions exhibit Markovnikov regioselectivity, and turnover frequencies are as high as 47,h,1 at 120,°C. The ring-size rate dependence of the primary alkenol cyclizations is 5>6, consistent with a sterically controlled transition state. The hydroalkoxylation/cyclization rates of terminal alkenols are slightly more rapid than those of internal alkenols, which suggests modest steric demands in the cyclic transition state. Cyclization rates of aryl-functionalized hydroxyalkenes are more rapid than those of the linear alkenols, whereas five- and five/six-membered spirobicyclic skeletons are also regioselectively closed. In cyclization of primary, sterically encumbered alkenols, turnover-frequency dependence on metal-ionic radius decreases by approximately 80-fold on going from La3+ (1.160,Å) to Lu3+ (0.977,Å), presumably reflecting steric impediments along the reaction coordinate. The overall rate law for alkenol hydroalkoxylation/cyclization is v,k[catalyst]1[alkenol]1. An observed ROH/ROD kinetic isotope effect of 2.48 (9) is suggestive of a catalytic pathway that involves kinetically significant intramolecular proton transfer. The present activation parameters,enthalpy (,H,)=18.2 (9),kcal,mol,1, entropy (,S,)=,17.0 (1.4),eu, and energy (Ea)=18.2 (8),kcal,mol,1,suggest a highly organized transition state. Proton scavenging and coordinative probing results suggest that the lanthanide triflates are not simply precursors of free triflic acid. Based on the kinetic and mechanistic evidence, the proposed catalytic pathway invokes hydroxyl and olefin activation by the electron-deficient Ln3+ center, and intramolecular H+ transfer, followed by alkoxide nucleophilic attack with ring closure. [source] | ||||||||||