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All total 32 Articles be foundMetal Ion Catalysis in the β-Elimination Reactions of N-[2-(4-Pyridyl)ethyl]quinuclidinium and N-[2-(2-Pyridyl)ethyl]quinuclidinium in Aqueous Solution
Alunni, Sergio,Del Giacco, Tiziana,De Maria, Paolo,Fifi, Giorgia,Fontana, Antonella,Ottavi, Laura,Tesei, Ilaria
, p. 3276 - 3281 (2004)
Catalysis of the β-elimination reaction of N-[2-(4-pyridyl)ethyl]quinuclidinium (1) and N-[2-(2-pyridyl)ethyl]quinuclidinium (2) by Zn2+ and Cd2+ in OH-/H2O (pH = 5.20-6.35, 50 °C, and μ = 1 M KCl) has been studied. In the presence of Zn2+, the elimination reactions of both isomers occur from the Zn2+-complexed substrates (C). The equilibrium constants for the dissociation of the Zn 2+-complexes are as follows: Kd = 0.012 ± 0.003 M (isomer 1) and Kd = 0.065 ± 0.020 M (isomer 2). The value of kH2OC for isomer 1 is 4.81 × 10-6 s -1. For isomer 2 both the rate constants for the water and OH--induced reaction of the Zn2+-complexed substrate could be measured, despite the low concentration of OH- in the investigated reaction mixture [kH2OC 0 = 1.97 × 10-6 s-1 and kOH-C = 21.9 M -1 s-1, respectively]. The measured metal activating factor (MetAF), i.e., the reactivity ratio between the complexed and the uncomplexed substrate, is 8.1 × 104 for the OH--induced elimination of 2. This high MetAF can be compared with the corresponding proton activating factor (Alunni, S.; Conti, A.; Palmizio Errico, R. J. Chem. Soc., Perkin Trans. 2 2000, 453), PAF = 1.5 × 106 and is in agreement with an E1cb irreversible mechanism (AxhD E* + DN) (Guthrie, R. D.; Jencks, W. P. Acc. Chem. Res. 1989, 22, 343). A value of kH2OC ≥ 23 × 10 -7 s-1 is estimated for the Cd2+-complexed isomer 2, while catalysis by Cd2+ has not been observed for isomer 1.
A study of the OH--induced β-elimination reactions of 2-(4-chloroethyl)pyridine, 2-(2-chloroethyl)pyridine, 1-methyl-2-(4-chloroethyl) pyridinium iodide and 1-methyl-2-(2-chloroethyl)pyridinium iodide in acetonitrile/water
Alunni, Sergio,Del Giacco, Tiziana,De Maria, Paolo,Fontana, Antonella,Gasbarri, Carla,Ottavi, Laura
, p. 6121 - 6123 (2004)
Second-order rate constants have been determined for the title reactions in OH-/H2O and in OH-/ (CH3CN/H 2O) [30/70, 60/40, and 85/15 (v/v) mixtures]. A relatively small increase in reactivity is observed for the four substrates upon increasing the percentage of CH3CN in the solvent mixture. The methyl activating factors (kOH-NCH3/kOH-N) are also slightly affected by the solvent composition. On the other hand, the high acceleration of the reaction by methylation of the pyridine ring amounts to 104-106 according to an E1cb mechanism.
Michael additions involving amino acid esters with alkenyl N-heterocycles
Kennedy, Sean H.,Klumpp, Douglas A.
, p. 10219 - 10225 (2017)
Michael addition has been achieved with a variety of amino acid esters and 2- or 4-vinylpyridine. Similar reactions were accomplished with an alkenyl-substituted pyrimidine, pyrazine, thiazole, quinoxaline, benzoxazole, and quinolone. In reactions at a prochiral center, modest diastereoselectivities were observed with the formation of the new stereogenic carbon. NMR experiments indicate that the addition reaction is reversible under acidic conditions.
Design and characterization of a heterocyclic electrophilic fragment library for the discovery of cysteine-targeted covalent inhibitors
Keeley,ábrányi-Balogh,Keseru
, p. 263 - 267 (2019)
A fragment library of electrophilic small heterocycles was characterized through cysteine-reactivity and aqueous stability tests that suggested their potential as covalent warheads. The analysis of theoretical and experimental descriptors revealed correlations between the electronic properties of the heterocyclic cores and their reactivity against GSH that are helpful in identifying suitable fragments for cysteines with specific nucleophilicity. The most important advantage of these fragments is that they show only minimal structural differences from non-electrophilic counterparts. Therefore, they could be used effectively in the design of targeted covalent inhibitors with minimal influence on key non-covalent interactions.
Construction of α-Amino Azines via Thianthrenation-Enabled Photocatalyzed Hydroarylation of Azine-Substituted Enamides with Arenes
Zhang, Yu-Lan,Wang, Gang-Hu,Wu, Yichen,Zhu, Chun-Yin,Wang, Peng
supporting information, p. 8522 - 8526 (2021/11/13)
α-Amino azines are widely found in pharmaceuticals and ligands. Herein, we report a practical method for accessing this class of compounds via photocatalyzed hydroarylation of azine-substituted enamides with the in situ-generated aryl thianthrenium salts as the radical precursor. This reaction features a broad substrate scope, good functional group tolerance, and mild conditions and is suitable for the late-stage installation of α-amino azines in complex structures.
INHIBITORS OF FIBROBLAST ACTIVATION PROTEIN
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Paragraph 0192, (2020/07/14)
Compounds and compositions for modulating fibroblast activation protein (FAP) are described. The compounds and compositions may find use as therapeutic agents for the treatment of diseases, including hyperproliferative diseases.
