2163-44-2Relevant academic research and scientific papers
Synthesis and initial SAR studies of 3,6-disubstituted pyrazolo[1,5-a]pyrimidines: A new class of KDR kinase inhibitors
Fraley, Mark E.,Hoffman, William F.,Rubino, Robert S.,Hungate, Randall W.,Tebben, Andrew J.,Rutledge, Ruth Z.,McFall, Rosemary C.,Huckle, William R.,Kendall, Richard L.,Coll, Kathleen E.,Thomas, Kenneth A.
, p. 2767 - 2770 (2002)
We have synthesized and evaluated the activity of 3,6-disubstituted pyrazolo[1,5-a]pyrimidines as a new class of KDR kinase inhibitors. Starting with screening lead 1, potency against isolated KDR was fully optimized with 3-thienyl and 4-methoxyphenyl substituents at the 6- and 3-positions (3g, KDR IC50=19 nM), respectively. The synthesis and SAR of these compounds are described.
Synthesis of Cyclopentenones through Rhodium-Catalyzed C-H Annulation of Acrylic Acids with Formaldehyde and Malonates
Yu, Shuling,Hong, Chao,Liu, Zhanxiang,Zhang, Yuhong
supporting information, p. 5054 - 5059 (2021/07/20)
An efficient rhodium-catalyzed protocol for the synthesis of cyclopentenones based on a three-component reaction of acrylic acids, formaldehyde, and malonates via vinylic C-H activation is reported. Exploratory studies showed that 5-alkylation of as-prepared cyclopentenones could be realized smoothly by the treatment of a variety of alkyl halides with a Na2CO3/MeOH solution. Excess formaldehyde and malonate led to a multicomponent reaction that afforded the multisubstituted cyclopentenones through a Michael addition.
A Case Study in Catalyst Generality: Simultaneous, Highly-Enantioselective Br?nsted- And Lewis-Acid Mechanisms in Hydrogen-Bond-Donor Catalyzed Oxetane Openings
Strassfeld, Daniel A.,Algera, Russell F.,Wickens, Zachary K.,Jacobsen, Eric N.
supporting information, p. 9585 - 9594 (2021/07/19)
Generality in asymmetric catalysis can be manifested in dramatic and valuable ways, such as high enantioselectivity across a wide assortment of substrates in a given reaction (broad substrate scope) or as applicability of a given chiral framework across a variety of mechanistically distinct reactions (privileged catalysts). Reactions and catalysts that display such generality hold special utility, because they can be applied broadly and sometimes even predictably in new applications. Despite the great value of such systems, the factors that underlie generality are not well understood. Here, we report a detailed investigation of an asymmetric hydrogen-bond-donor catalyzed oxetane opening with TMSBr that is shown to possess unexpected mechanistic generality. Careful analysis of the role of adventitious protic impurities revealed the participation of competing pathways involving addition of either TMSBr or HBr in the enantiodetermining, ring-opening event. The optimal catalyst induces high enantioselectivity in both pathways, thereby achieving precise stereocontrol in fundamentally different mechanisms under the same conditions and with the same chiral framework. The basis for that generality is analyzed using a combination of experimental and computational methods, which indicate that proximally localized catalyst components cooperatively stabilize and precisely orient dipolar enantiodetermining transition states in both pathways. Generality across different mechanisms is rarely considered in catalyst discovery efforts, but we suggest that it may play a role in the identification of so-called privileged catalysts.
Highly Enantioselective, Hydrogen-Bond-Donor Catalyzed Additions to Oxetanes
Strassfeld, Daniel A.,Wickens, Zachary K.,Picazo, Elias,Jacobsen, Eric N.
supporting information, p. 9175 - 9180 (2020/07/13)
A precisely designed chiral squaramide derivative is shown to promote the highly enantioselective addition of trimethylsilyl bromide (TMSBr) to a broad variety of 3-substituted and 3,3-disubstituted oxetanes. The reaction provides direct and general access to synthetically valuable 1,3-bromohydrin building blocks from easily accessed achiral precursors. The products are readily elaborated both by nucleophilic substitution and through transition-metal-catalyzed cross-coupling reactions. The enantioselective catalytic oxetane ring opening was employed as part of a three-step, gram-scale synthesis of pretomanid, a recently approved medication for the treatment of multidrug-resistant tuberculosis. Heavy-atom kinetic isotope effect (KIE) studies are consistent with enantiodetermining delivery of bromide from the H-bond-donor (HBD) catalyst to the activated oxetane. While the nucleophilicity of the bromide ion is expected to be attenuated by association to the HBD, overall rate acceleration is achieved by enhancement of Lewis acidity of the TMSBr reagent through anion abstraction.
Electrochemistry-Enabled Ir-Catalyzed Vinylic C-H Functionalization
Yang, Qi-Liang,Xing, Yi-Kang,Wang, Xiang-Yang,Ma, Hong-Xing,Weng, Xin-Jun,Yang, Xiang,Guo, Hai-Ming,Mei, Tian-Sheng
supporting information, p. 18970 - 18976 (2019/12/04)
Synergistic use of electrochemistry and organometallic catalysis has emerged as a powerful tool for site-selective C-H functionalization, yet this type of transformation has thus far mainly been limited to arene C-H functionalization. Herein, we report the development of electrochemical vinylic C-H functionalization of acrylic acids with alkynes. In this reaction an iridium catalyst enables C-H/O-H functionalization for alkyne annulation, affording α-pyrones with good to excellent yields in an undivided cell. Preliminary mechanistic studies show that anodic oxidation is crucial for releasing the product and regeneration of an Ir(III) intermediate from a diene-Ir(I) complex, which is a coordinatively saturated, 18-electron complex. Importantly, common chemical oxidants such as Ag(I) or Cu(II) did not give significant amounts of the desired product in the absence of electrical current under otherwise identical conditions.
Computational and experimental studies on copper-mediated selective cascade C-H/N-H annulation of electron-deficient acrylamide with arynes
Chen, Chao,Hao, Yu,Zhang, Ting-Yu,Pan, Jin-Long,Ding, Jun,Xiang, Heng-Ye,Wang, Man,Ding, Tong-Mei,Duan, Abing,Zhang, Shu-Yu
supporting information, p. 755 - 758 (2019/01/21)
An efficient and convenient copper-mediated method has been developed to achieve direct cascade C-H/N-H annulation to synthesize 2-quinolinones from electron-deficient acrylamides and arynes. This method highlights an emerging but simple strategy to transform inert C-H bonds into versatile functional groups in organic synthesis to provide a new method of synthesizing 2-quinolinones efficiently. Mechanistic investigations by experimental and density functional theory (DFT) studies suggest that an organometallic C-H activation via a Cu(iii) intermediate is likely to be involved in the reaction.
Tf2O-Promoted Intramolecular Schmidt Reaction of the ω-Azido Carboxylic Acids
Wang, Xue-Juan,Su, Yan,Li, Rui,Gu, Peiming
supporting information, p. 5816 - 5824 (2018/05/14)
A designed Tf2O-promoted intramolecular Schmidt reaction of 2-substituted ω-azido carboxylic acids was demonstrated. Tf2O was used as an activation reagent for the carboxylic acid, and ω-azido anhydride was in situ generated, releasing a molecular TfOH, which acted as an acid promoter for the Schmidt process. A series of 2-substituted pyrrolidines was produced and acetylated for better purification. The strategy was also efficient for conversion of a 4-substituted ω-azido carboxylic acid to the tricyclic lactam.
S - Cis Diene Conformation: A New Bathochromic Shift Strategy for Near-Infrared Fluorescence Switchable Dye and the Imaging Applications
Chen, Hsiang-Jung,Chew, Chee Ying,Chang, En-Hao,Tu, Yu-Wei,Wei, Li-Yu,Wu, Bo-Han,Chen, Chien-Hung,Yang, Ya-Ting,Huang, Su-Chin,Chen, Jen-Kun,Chen, I-Chia,Tan, Kui-Thong
supporting information, p. 5224 - 5234 (2018/04/23)
In this paper, we present a novel charge-free fluorescence-switchable near-infrared (IR) dye based on merocyanine for target specific imaging. In contrast to the typical bathochromic shift approach by extending π-conjugation, the bathochromic shift of our merocyanine dye to the near-IR region is due to an unusual S-cis diene conformer. This is the first example where a fluorescent dye adopts the stable S-cis conformation. In addition to the novel bathochromic shift mechanism, the dye exhibits fluorescence-switchable properties in response to polarity and viscosity. By incorporating a protein-specific ligand to the dye, the probes (for SNAP-tag and hCAII proteins) exhibited dramatic fluorescence increase (up to 300-fold) upon binding with its target protein. The large fluorescence enhancement, near-IR absorption/emission, and charge-free scaffold enabled no-wash and site-specific imaging of target proteins in living cells and in vivo with minimum background fluorescence. We believe that our unconventional approach for a near-IR dye with the S-cis diene conformation can lead to new strategies for the design of near-IR dyes.
Nucleophilic Reactivities of 2-Substituted Malonates
Puente, ángel,He, Shanshan,Corral-Bautista, Francisco,Ofial, Armin R.,Mayr, Herbert
supporting information, p. 1841 - 1848 (2016/05/09)
Kinetics of the reactions of 2-substituted malonate anions and 5-substituted Meldrum's acid anions with benzhydrylium ions and structurally related quinone methides have been monitored in dimethyl sulfoxide solution at 20 °C. The resulting second-order rate constants followed the correlation lg k(20 °C) = sN(E + N), which allowed the nucleophile-specific parameters N and sN to be calculated for these highly stabilized carbanions and to integrate them in our comprehensive nucleophilicity scale. Given that the reactions of the benzhydrylium ions with the anions derived from 5-aryl-substituted Meldrum's acids did not proceed to completion, the corresponding equilibrium constants could be determined. In combination with available data for pyridines and benzoate ions, these equilibrium constants provide a direct comparison of the strengths of C-, N-, and O-centered Lewis bases with respect to C-centered Lewis acids.
New pseudodimeric aurones as palm pocket inhibitors of Hepatitis C virus RNA-dependent RNA polymerase
Meguellati, Amel,Ahmed-Belkacem, Abdelhakim,Nurisso, Alessandra,Yi, Wei,Brillet, Rozenn,Berqouch, Nawel,Chavoutier, Laura,Fortuné, Antoine,Pawlotsky, Jean-Michel,Boumendjel, Ahcène,Peuchmaur, Marine
, p. 217 - 229 (2016/04/05)
The NS5B RNA-dependent RNA polymerase (RdRp) is a key enzyme for Hepatitis C Virus (HCV) replication. In addition to the catalytic site, this enzyme is characterized by the presence of at least four allosteric pockets making it an interesting target for development of inhibitors as potential anti-HCV drugs. Based on a previous study showing the potential of the naturally occurring aurones as inhibitors of NS5B, we pursued our efforts to focus on pseudodimeric aurones that have never been investigated so far. Hence, 14 original compounds characterized by the presence of a spacer between the benzofuranone moieties were synthesized and investigated as HCV RdRp inhibitors by means of an in vitro assay. The most active inhibitor, pseudodimeric aurone 4, induced high inhibition activity (IC50 Combining double low line 1.3 1/4M). Mutagenic and molecular modeling studies reveal that the binding site for the most active derivatives probably is the palm pocket I instead of the thumb pocket I as for the monomeric derivatives.
