Search results for "ALK"
showing 10 items of 4314 documents
Solvent-trap reaction of triazolinediones with simple alkenes: An experimental/theoretical study of thermodynamic and kinetic parameters This work is…
2015
The reaction of N-phenyltriazolinedione with simple alkyl-substituted alkenes in a series of simple alcohols as nucleophilic solvents affords two products: a solvent-addition product (trap) and the ene adduct. Herein we present different experimental data which allow the estimation of different kinetic parameters (ΔΔH ≠ene,trap and ΔΔS ≠ene,trap ). The values of those parameters are found to be lower with a longer nucleophile-solvent molecule. Solvent isotope effects are also estimated and found in favour of the heavier (and smaller) deuterated compounds. Results from competition experiments in equimolar binary mixtures of different alcohols as solvents also point to the prevalence of the s…
Triazolopyridines 21.1 The stereochemistry of 1-[1,2,3]triazolo [1,5-a] pyridin-7-yl-4-(2h-[1,2,3]triazol-4-yl)-1,3-butadienes and triazolo ring open…
2002
The synthesis and NMR study of the geometry of 1-[1,2,3]triazolo[1,5-a]pyridin-7-yl-4-(2H- [1,2,3]triazol-4-yl)-1,3-butadienes 1a, 1b, 5 and of new 1-(6-substituted-2-pyridyl)-4-(2H- [1,2,3]triazol-4-yl)-1,3-butadienes 8-10 is reported. The stereochemistry of all butadienes studied is 1E, 3E except for compound 5 that is the 1Z, 3Z stereoisomer of 1a. Abarca Gonzalez, Belen, Belen.Abarca@uv.es ; Ballesteros Campos, Rafael, Rafael.Ballesteros@uv.es
Catalytic Enantioselective Conjugate Alkynylation of α,β-Unsaturated 1,1,1-Trifluoromethyl Ketones with Terminal Alkynes.
2016
The first catalytic enantioselective conjugate alkynylation of α,β-unsaturated 1,1,1-trifluoromethyl ketones has been carried out. Terminal alkynes and 1,3-diynes were treated with trifluoromethyl ketones in the presence of a low catalytic load of a CuI-MeOBIPHEP complex (2.5 mol %) and triethylamine (10 mol %) to give the corresponding trifluoromethyl ketones bearing a propargylic stereogenic center at the β position with good yields and excellent enantiomeric excesses in most of the cases. No 1,2-addition products were formed under the reaction conditions. The procedure showed broad substrate scope for alkyne, diyne, and enone. A rationale for the observed stereochemistry has been provide…
Diarylprolinol as a Ligand for Enantioselective Alkynylation of Cyclic Imines
2017
An easily accessible prolinol derived ligand, (S)-bis(3,5-bis(trifluoromethyl)phenyl)(pyrrolidin-2-yl)methanol, has been efficiently applied in the catalytic enantioselective addition of terminal alkynes to cyclic imines using dimethylzinc (Me2Zn) under mild reaction conditions. The developed catalytic system led to chiral propargylic sulfamidates with high yields (up to 97%) and excellent enantioselectivities (up to 97% ee).
Enantioselective Zirconium-Catalyzed Friedel−Crafts Alkylation of Pyrrole with Trifluoromethyl Ketones
2009
The first catalytic enantioselective Friedel-Crafts alkylation of pyrrole with 2,2,2-trifluoroacetophenones to give pyrroles with a trifluoromethyl-substituted tertiary alcohol moiety bearing a quaternary stereogenic center is described. The reaction is achieved in the presence of a 3,3'-dibromo-BINOL-Zr(IV) complex to give the expected products with high yields (up to 98%) and good enantioselectivities (up to 93% ee). The absolute stereochemistry of the products has been determined by chemical correlation.
Catalytic asymmetric conjugate addition of terminal alkynes to β-trifluoromethyl α,β-enones.
2014
The first enantioselective conjugate alkynylation of β-trifluoromethyl α,β-enones using terminal alkynes and a taniaphos–Cu(I) complex as catalyst is described. Ketones bearing a trifluoromethylated propargylic chiral centre in the β-position were obtained with good yields and high enantiomeric excesses (up to 99%).
Highly enantioselective copper(I)-catalyzed conjugate addition of terminal alkynes to 1,1-difluoro-1-(phenylsulfonyl)-3-en-2-ones: new ester/amide su…
2013
A highly enantioselective copper-catalyzed conjugate alkynylation of monoactivated enones, namely 1,1-difluoro-1-(phenylsulfonyl)-3-en-2-ones, is described. The reaction products are obtained with good yields and excellent enantioselectivities (from 92 to 99% ee). The β-alkynylated difluoro(phenylsulfonyl) ketones can be converted into the corresponding β-alkynylated difluoro- and trifluoromethyl ketones, esters and amides. This is the first example on the use of 1,1-difluoro-1-(phenylsulfonyl)-3-en-2-ones as substrates in an enantioselective reaction, which have been shown to be new ester/amide surrogates.
Hyperfine couplings ofN-alkoxy-N-polynitrophenylaminyl radicals determined by ENDOR and TRIPLE resonance spectroscopy
1995
Lead tetraacetate one-electron oxidation of nine different N-alkoxy-2,6-dinitroanilines substituted with trifluoromethyl, methyl and nitro groups in position 4 yielded aminyl radicals for which hyperfine couplings were measured by ENDOR and TRIPLE resonance spectroscopy. The optimum temperature range for proton ENDOR and general TRIPLE resonance measurements of aminyl radicals was 210–250 K and for nitrogen ENDOR 260 K in toluene. Further lowering for the temperature rapidly decreased the EPR intensity. The concentration of the sample and the amount of oxidant were optimized for obtaining ENDOR spectra. The relative signs of the hyperfine couplings of nitrogens, fluorines and protons were d…
Synthesis, Structural Characterisation and Reactivity of New Dinuclear Monocyclopentadienyl Imidoniobium and ‐tantalum Complexes − X‐ray Crystal Stru…
2004
The preparation of a family of dinuclear monocyclopentadienyl imidoniobium and -tantalum complexes was achieved by two different synthetic routes. The diimido complexes [{M(Cp′)Cl2}2(μ-1,i-NC6H4N)] [Cp′ = η5-C5H4SiMe3, M = Nb, i = 4 (1); Cp′ = η5-C5H4SiMe3, M = Nb, i = 3 (2); Cp′ = η5-C5H4SiMe3, M = Nb, i = 2 (3); Cp′ = η5-C5Me5, M = Nb, i = 4 (4); Cp′ = η5-C5Me5, M = Nb, i = 3 (5); Cp′ = η5-C5H4SiMe3, M = Ta, i = 4 (6); Cp′ = η5-C5H4SiMe3, M = Ta, i = 3 (7)] were prepared by the reaction of one equivalent of the trichloro precursor [{MCl3}2(μ-1,i-NC6H4N)] (M = Nb, Ta, i = 4, 3 or 2) with two equivalents of either C5H4(SiMe3)2 or C5Me5(SiMe3). Complexes 1−7 can also be prepared by the react…
Tributyltin(Iv) butyrate: A novel epigenetic modifier with er stress-and apoptosis-inducing properties in colon cancer cells
2021
Organotin(IV) compounds are a class of non-platinum metallo-conjugates exhibiting antitumor activity. The effects of different organotin types has been related to several mechanisms, including their ability to modify acetylation protein status and to promote apoptosis. Here, we focus on triorganotin(IV) complexes of butyric acid, a well-known HDAC inhibitor with antitumor properties. The conjugated compounds were synthesized and characterised by FTIR spectroscopy, multi-nuclear (1H, 13C and 119Sn) NMR, and mass spectrometry (ESI-MS). In the triorganotin(IV) complexes, an anionic monodentate butyrate ligand was observed, which coordinated the tin atom on a tetra-coordinated, monomeric enviro…