Lanthanide Triflates Research Articles

ChemInform Abstract: Activation of Disarmed 2‐O‐Alkoxycarbonylated Glycosyl Trichloroacetimidates with Lanthanoid Triflates: An Efficient Approach for the Synthesis of 1,2‐trans Glycosides.

AbstractChemInform 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.

Application of Lewis acid catalyzed tropone [6+4] cycloadditions to the synthesis of the core of CP-225,917.

The carbocyclic core of CP-225,917 and CP-263,114 is accessible through the [6+4] cycloaddition of a tropone with a 2-substituted cyclopentadiene. Examination of this reaction has revealed for the first time that this cycloaddition process is catalyzed by Lewis acids, including lanthanide triflates. Cycloadditions of several mono-, di-, and trisubstituted tropones with 2-silyloxycyclopentadienes using ZnCl(2) catalysis are found to proceed in good yield and, in many cases, with excellent diastereoselectivity. Subsequent transformation to the core of the CP-molecules involves a site-selective Baeyer-Villiger oxidation of a tricyclic diketone, followed by a syn-elimination process. [reaction: see text]

ChemInform Abstract: Lanthanoid Triflate Catalyzed Three‐Component Synthesis of α‐Amino Phosphonates in Ionic Liquids. A Catalyst Reactivity and Reusability Study.

AbstractChemInform 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.

Recent progress in lanthanide-catalyzed organic reactions in protic media

Lanthanide triflates are stable in water. It is possible for lanthanides to undergo many organic reactions in environmentally friendly solvents. This makes lanthanides very promising in the field of green chemistry. This review describes the recent development of the lanthanidecatalyzed organic reactions in protic solvents. Those reactions include Diels-Alder, Aldol, Allylation, acetalization, pericyclization, radical reactions as well as some newlydeveloped lanthnidesbased catalysts.

Anhydrous lanthanide Schiff base complexes and their preparation using lanthanide triflate derived amides.

The complex bis-5,5‘-(1,3-propanediyldiimino)-2,2-dimethyl-4-hexen-3-onato samarium bis(trimethylsilyl)amido is a solvent- and halide-free anhydrous, monomeric lanthanide Schiff base complex. It was synthesized from triflate-derived homoleptic Sm[N(TMS)2]3 and isolated in excellent yields and analytical purity. For larger rare earths, only dimers were observed using analogous reaction pathways.

Study of Lanthanide Triflates as New Curing Initiators for Cycloaliphatic Epoxy Resins

Lanthanide triflates, a new class of cationic initiators, have been tested as curing agents for cycloaliphatic epoxy resins. Several metal salts in various proportions have been used. The triflate salts were compared with the conventional BF 3 MEA system. the processes have been kinetically evaluated by isoconversional analysis, time and temperature predictions have been made. Their mechanical properties have been evaluated by dynamic mechanical thermal analysis (DMTA).

Reactions oftBu-Calix[6]arene with Lanthanide Triflates: Synthesis and Crystal Structure Determination of Novel Bimetallic Calixarene Complexes of La, Sm and Yb

The reactions of tBu-calix[6]arene (H6L) with Ln(O3SCF3)3 (Ln = La, Sm, Yb) were used to isolate [{La(O3SCF3)(pyridine)7}2H2L] (1), [{Sm(O3SCF3)(pyridine)4}2H2L] (2) and [{Yb(O3SCF3)(terpyridine)(pyridine)}2H2L] (3), three novel bimetallic calixarene complexes of the lanthanides. The solid state structures of 2 and 3 were determined by X-ray crystallography revealing compounds where the two metal cations are anchored on both sides of the macrocycle in the 1,2,3-alternate conformation. Compounds 1−3 are the first bis-alkoxy triflate species {M(OR)2(O3SCF3)} to be characterized in lanthanide coordination chemistry.

A novel approach to the stereoselective synthesis of β- d-mannopyranosides

A non-covalent version of the intramolecular aglycon delivery methodology has been demonstrated for the stereoselective formation of β- d-mannopyranoside in the presence of lanthanide(III) triflate.

Lanthanide triflate catalyzed 1,3-dipolar cycloaddition reactions: stereoselective synthesis of indenoisoxazolidines

Substituted indenones reacted smoothly with a variety of in situ generated nitrones in the presence of lanthanide triflates to give exclusive exo 1,3-dipolar cycloaddition products in high yield. Judicious choice of the nitrone substituents allowed for further modification of the indenoisoxazolidine core to the corresponding indenoisoxazoline and indenoisoxazole analogs in high yield.

Stereocontrol in radical polymerization.

The stereospecific radical polymerization of vinyl esters, methacrylates, and alpha-substituted acrylates was studied. Fluoroalcohols, as a solvent, have remarkable effects on the stereoregularity of the radical polymerizations of vinyl acetate, vinyl pivalate, and vinyl benzoate, affording polymers rich in syndiotacticity, heterotacticity, and isotacticity, respectively. This method was successfully applied to the polymerization of methacrylates to give syndiotactic polymers. The steric repulsion between the entering monomer and the chain-end monomeric unit bound by the solvent through hydrogen bonding is important for the stereochemical control in these systems. Lewis acid catalysts, such as lanthanide trifluoromethanesulfonates and zinc salts, were also effective for the stereocontrol during the radical polymerization of methyl methacrylate, to reduce the syndiotacticity and alpha-(alkoxymethyl)acrylates to synthesize isotactic and syndiotactic polymers. Radical polymerization of the methacrylates bearing a bulky ester group, such as the triphenylmethyl methacrylate derivatives, gave highly isotactic polymers, as in the case of anionic polymerization. In addition, the control of one-handed helical conformation was attained in the radical polymerization of 1-phenyldibenzosuberyl methacrylate using chiral neomenthanethiol or cobalt(II) complexes as an additive.

Stereocontrol in radical polymerization

The stereospecific radical polymerization of vinyl esters, methacrylates, and α-substituted acrylates was studied. Fluoroalcohols, as a solvent, have remarkable effects on the stereoregularity of the radical polymerizations of vinyl acetate, vinyl pivalate, and vinyl benzoate, affording polymers rich in syndiotacticity, heterotacticity, and isotacticity, respectively. This method was successfully applied to the polymerization of methacrylates to give syndiotactic polymers. The steric repulsion between the entering monomer and the chain-end monomeric unit bound by the solvent through hydrogen bonding is important for the stereochemical control in these systems. Lewis acid catalysts, such as lanthanide trifluoromethanesulfonates and zinc salts, were also effective for the stereocontrol during the radical polymerization of methyl methacrylate, to reduce the syndiotacticity and α-(alkoxymethyl)acrylates to synthesize isotactic and syndiotactic polymers. Radical polymerization of the methacrylates bearing a bulky ester group, such as the triphenylmethyl methacrylate derivatives, gave highly isotactic polymers, as in the case of anionic polymerization. In addition, the control of one-handed helical conformation was attained in the radical polymerization of 1-phenyldibenzosuberyl methacrylate using chiral neomenthanethiol or cobalt(II) complexes as an additive. © 2000 John Wiley & Sons, Inc. and The Japan Chemical Journal Forum Chem Rec 1:46–52, 2001

Highly Stereoselective Aldol Reaction of Chiral 3-(p-Tolylsulfinyl)furfural with Silyl Ketene Acetal Catalyzed by Lanthanide Triflate

Highly Stereoselective Aldol Reaction of Chiral 3-(<i>p</i>-Tolylsulfinyl)furfural with Silyl Ketene Acetal Catalyzed by Lanthanide Triflate

Lanthanide trifluoromethanesulfonate-catalyzed asymmetric aldol reactions in aqueous media.

[figure: see text] Catalytic asymmetric aldol reactions catalyzed by lanthanide trifluoromethanesulfonates in aqueous media have been realized for the first time using a chiral crown ether.

ChemInform Abstract: Addition of Silyl Ketene Acetals to Nitrones Catalyzed by Lanthanoid Triflates.

ChemInform Abstract: Addition of Silyl Ketene Acetals to Nitrones Catalyzed by Lanthanoid Triflates.

ChemInform Abstract: Lanthanoid Triflate Catalyzed Biginelli Reaction. One-Pot Synthesis of Dihydropyrimidinones under Solvent-Free Conditions.

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.

Addition of Silyl Ketene Acetals to Nitrones Catalyzed by Lanthanide Triflates

α-Aryl- N-phenyl nitrones reacted with silyl ketene acetals mediated by lanthanum trifloromethanesulfonate (triflate) to afford the addition product in excellent yield under mild conditions. α-Aryl- N- tert-butyl nitrone reacted with ethyl trimethylsilylacetate to yield the unexpected α,β-unsaturated ester in a 100% E-form. A possible mechanism for the process is discussed.

Study of lanthanide triflates as new curing initiators for DGEBA

A new class of cationic initiators, lanthanide triflates, has been studied in the curing of diglycidyl ether of bisphenol-A (DGEBA). The kinetics of this process has been evaluated by the isoconversional method that has been proved as an excellent tool to predict the technical parameters of this process. The thermal stability of the crosslinked materials has been studied by thermogravimetric analysis (TGA) and their mechanical characteristics by dynamomechanic thermal analysis (DMTA).

Lanthanide triflate catalyzed Biginelli reaction. one-pot synthesis of dihydropyrimidinones under solvent-free conditions.

Lanthanide triflate catalyzed Biginelli reaction. one-pot synthesis of dihydropyrimidinones under solvent-free conditions.

Synthesis of furo[3,2‐c]‐ and pyrano[3,2‐c ]quinolines by lanthanide triflate catalyzed imino‐Diels‐Alder reaction

AbstractImino Diels‐Alder reaction of imines with 2,3‐dihydrofuran or 3,4‐dihydro‐2H‐pyran proceeded smoothly in the presence of a catalytic amount (0.5 mol %) of ytterbium triflate to afford furo[3,2‐c]‐ and pyrano[3,2‐c] quinolines conveniently in high yield.

Investigation of Mn(III)-Based Oxidative Free Radical Cyclization Reactions toward the Synthesis of Triptolide: The Effects of Lanthanide Triflates and Substituents on Stereoselectivity

Mn(III)-mediated oxidative free radical cyclization reactions are useful for construction of polycyclic compounds. In the total synthesis of triptolide (3) and its related compounds, construction of tricyclic skeletons 4 and 5 was achieved by the Mn(OAc)3-mediated oxidative radical cyclization of a series of acyclic precursors 6−9. The addition of a catalytic amount of lanthanide triflates was found to significantly improve the rate and stereoselectivity of those radical cyclization reactions. The effects of the benzylic oxygen substituents and α-substituents (chloro and methyl) on the radical cyclization reactions were also investigated. Transition-state models were proposed to explain the observed stereoselectivity.