273-21-2Relevant articles and documents
XRD studies, vibrational spectra, andmolecular structure of 1h-imidazo [4,5-b]pyridine based on DFT quantum chemical calculations
Dyminska,Gagor,Maczka,Weglinskia,Hanuzaa
, p. 1021 - 1029 (2010)
The molecular structures and vibrational properties of 1H-imidazo[4,5-b]pyridine in its monomeric and dimeric forms are analyzed and compared to the experimental results derived from the X-ray diffraction (XRD), infrared (IR), and Raman studies. The theoretical data are discussed on the basis of density functional theory (DFT) quantum chemical calculations using Lee-Yang-Parr correlation functional (B3LYP) and 6-31G(d,p) basis. This compound crystallizes in orthorhombic structure, space group Pna21(C2v9) and Z = 4. The planar conformation of the skeleton and presence of the N-H· · ·N hydrogen bond was found to be characteristic for the studied system. The temperature dependence of IR and Raman modes was studied in the range 4-294 K and 8-295 K, respectively. The normal modes, which are unique for the imidazopyridine derivatives are identified.
Convenient synthesis of imidazo[1,5-a]pyrimidine derivatives and their unusual recyclization into 3H-imidazo[4,5-b]pyridine derivatives
Smirnova, Olga V.,Tolkunov, Andrew S.,Tolkunov, Sergei V.,Tolkunov, Valery S.
, p. 554 - 559 (2021/06/14)
[Figure not available: see fulltext.] New derivatives of imidazo[1,5-a]pyrimidine have been synthesized by cyclization of in situ generated 1H-imidazol-4(5)-amine with 1,3-diketones or malondialdehyde derivatives. Utilization of asymmetrical 1,3-diketones leads to the formation of a mixture of regioisomers. The discovered conversion of imidazo[1,5-a]pyrimidine core into 3H-imidazo[4,5-b]pyridine that takes place only under acidic conditions can be considered as a new version of Dimroth rearrangement involving cleavage of C–N bond and formation of C–C bond.
Discovery and characterization of an acridine radical photoreductant
MacKenzie, Ian A.,Wang, Leifeng,Onuska, Nicholas P. R.,Williams, Olivia F.,Begam, Khadiza,Moran, Andrew M.,Dunietz, Barry D.,Nicewicz, David A.
, p. 76 - 80 (2020/04/17)
Photoinduced electron transfer (PET) is a phenomenon whereby the absorption of light by a chemical species provides an energetic driving force for an electron-transfer reaction1–4. This mechanism is relevant in many areas of chemistry, including the study of natural and artificial photosynthesis, photovoltaics and photosensitive materials. In recent years, research in the area of photoredox catalysis has enabled the use of PET for the catalytic generation of both neutral and charged organic free-radical species. These technologies have enabled previously inaccessible chemical transformations and have been widely used in both academic and industrial settings. Such reactions are often catalysed by visible-light-absorbing organic molecules or transition-metal complexes of ruthenium, iridium, chromium or copper5,6. Although various closed-shell organic molecules have been shown to behave as competent electron-transfer catalysts in photoredox reactions, there are only limited reports of PET reactions involving neutral organic radicals as excited-state donors or acceptors. This is unsurprising because the lifetimes of doublet excited states of neutral organic radicals are typically several orders of magnitude shorter than the singlet lifetimes of known transition-metal photoredox catalysts7–11. Here we document the discovery, characterization and reactivity of a neutral acridine radical with a maximum excited-state oxidation potential of ?3.36 volts versus a saturated calomel electrode, which is similarly reducing to elemental lithium, making this radical one of the most potent chemical reductants reported12. Spectroscopic, computational and chemical studies indicate that the formation of a twisted intramolecular charge-transfer species enables the population of higher-energy doublet excited states, leading to the observed potent photoreducing behaviour. We demonstrate that this catalytically generated PET catalyst facilitates several chemical reactions that typically require alkali metal reductants and can be used in other organic transformations that require dissolving metal reductants.
In Situ Formation of Frustrated Lewis Pairs in a Water-Tolerant Metal-Organic Framework for the Transformation of CO2
Shyshkanov, Serhii,Nguyen, Tu N.,Ebrahim, Fatmah Mish,Stylianou, Kyriakos C.,Dyson, Paul J.
supporting information, p. 5371 - 5375 (2019/03/17)
Frustrated Lewis pairs (FLPs) consist of sterically hindered Lewis acids and Lewis bases, which provide high catalytic activity towards non-metal-mediated activation of “inert” small molecules, including CO2 among others. One critical issue of homogeneous FLPs, however, is their instability upon recycling, leading to catalytic deactivation. Herein, we provide a solution to this issue by incorporating a bulky Lewis acid-functionalized ligand into a water-tolerant metal-organic framework (MOF), named SION-105, and employing Lewis basic diamine substrates for the in situ formation of FLPs within the MOF. Using CO2 as a C1-feedstock, this combination allows for the efficient transformation of a variety of diamine substrates into benzimidazoles. SION-105 can be easily recycled by washing with MeOH and reused multiple times without losing its identity and catalytic activity, highlighting the advantage of the MOF approach in FLP chemistry.
Cobalt-catalyzed synthesis of N-containing heterocycles: Via cyclization of ortho -substituted anilines with CO2/H2
Ke, Zhengang,Yu, Bo,Wang, Huan,Xiang, Junfeng,Han, Juanjuan,Wu, Yunyan,Liu, Zhenghui,Yang, Peng,Liu, Zhimin
, p. 1695 - 1701 (2019/04/10)
The CO2-involved synthesis of chemicals is of great significance from the green and sustainable chemistry viewpoint. Herein, we report a non-noble metal catalytic system composed of CoF2, CsF and P(CH2CH2PPh2)3 (denoted as PP3) for the synthesis of N-containing heterocycles from ortho-substituted anilines and CO2/H2. Mechanism investigation indicates that [Co(PP3)H(CO2)]+ is a catalytically active intermediate under working conditions; and CsF plays important roles in activating ortho-substituted anilines via hydrogen bond interactions, thus promoting the formation of the final products. This catalytic system is highly efficient, and allows a wide scope of ortho-substituted anilines, together with excellent functional group tolerance, affording various N-containing heterocycles in good to excellent yields.
Fluorescing Isofunctional Ribonucleosides: Assessing Adenosine Deaminase Activity and Inhibition
Ludford, Paul T.,Rovira, Alexander R.,Fin, Andrea,Tor, Yitzhak
, p. 718 - 726 (2019/03/05)
The enzymatic conversion of isothiazolo[4,3-d]pyrimidine-based adenosine (tzA) and 2-aminoadenosine (tz2-AA) analogues to the corresponding isothiazolo[4,3-d]pyrimidine-based inosine (tzI) and guanosine (tzG) derivatives is evaluated and compared to the conversion of native adenosine to inosine. Henri–Michaelis–Menten analyses provides the foundation for a high-throughput screening assay, and the efficacy of the assay is showcased by fluorescence-based analysis of tzA conversion to tzI in the presence of known and newly synthesized inhibitors.
Synthesis and Antibacterial Activity of Novel 4″-O-desosaminyl clarithromycin derivatives with 11, 12-arylalkyl side chains
Zhao, Zhe-Hui,Zhu, Di,Zhang, Xiao-Xi,Luo, Zhi-Gang,Lei, Ping-Sheng
, p. 1 - 9 (2018/04/24)
A series of novel 4″-O-desosaminyl clarithromycin derivatives with 11, 12-arylalkyl side chains was synthesized by coupling 6-deoxy-desosamine donors (18, 19) with 4″-OH of compounds 5a–c. The activities of the target compounds were tested against a series of macrolide-sensitive and macrolide-resistant pathogens. Some of them showed activities against macrolide sensitive and resistant pathogens, and compounds 21d and 21e displayed significant improvement of activities against resistant pathogens.
Atom-Specific Mutagenesis Reveals Structural and Catalytic Roles for an Active-Site Adenosine and Hydrated Mg2+ in Pistol Ribozymes
Neuner, Sandro,Falschlunger, Christoph,Fuchs, Elisabeth,Himmelstoss, Maximilian,Ren, Aiming,Patel, Dinshaw J.,Micura, Ronald
supporting information, p. 15954 - 15958 (2017/11/21)
The pistol RNA motif represents a new class of self-cleaving ribozymes of yet unknown biological function. Our recent crystal structure of a pre-catalytic state of this RNA shows guanosine G40 and adenosine A32 close to the G53–U54 cleavage site. While the N1 of G40 is within 3.4 ? of the modeled G53 2′-OH group that attacks the scissile phosphate, thus suggesting a direct role in general acid–base catalysis, the function of A32 is less clear. We present evidence from atom-specific mutagenesis that neither the N1 nor N3 base positions of A32 are involved in catalysis. By contrast, the ribose 2′-OH of A32 seems crucial for the proper positioning of G40 through a H-bond network that involves G42 as a bridging unit between A32 and G40. We also found that disruption of the inner-sphere coordination of the active-site Mg2+ cation to N7 of G33 makes the ribozyme drastically slower. A mechanistic proposal is suggested, with A32 playing a structural role and hydrated Mg2+ playing a catalytic role in cleavage.
Atmospheric CO2 promoted synthesis of N-containing heterocycles over B(C6F5)3 catalyst
Gao, Xiang,Yu, Bo,Mei, Qingqing,Yang, Zhenzhen,Zhao, Yanfei,Zhang, Hongye,Hao, Leiduan,Liu, Zhimin
, p. 8282 - 8287 (2016/10/11)
B(C6F5)3 combined with atmospheric CO2 was found to be highly effective for the cyclization of ortho-substituted aniline derivatives with N,N-dimethylformamide (DMF), and a series of N-containing heterocycles including benzothiazoles, benzimidazoles, quinazolinone and benzoxazole were obtained in good to excellent yields.
Microwave-Assisted C-2 Direct Alkenylation of Imidazo[4,5-b]pyridines: Access to Fluorescent Purine Isosteres with Remarkably Large Stokes Shifts
Baladi, Tom,Granzhan, Anton,Piguel, Sandrine
, p. 2421 - 2434 (2016/06/01)
We describe herein the first C-2 direct alkenylation of the valuable 3H-imidazo[4,5-b]pyridine promoted by microwave-assisted Pd/Cu co-catalysis. The reaction is rapid and compatible with a wide range of functional groups either on the imidazo[4,5-b]pyridine ring or on the styryl bromides thereby leading to the isolation of 23 compounds with moderate to good yields. The relevance of this method is demonstrated by its application to the synthesis of new cross-conjuguated push-pull 2-vinyl- and 2-alkynylimidazo[4,5-b]pyridines characterized by satisfactory fluorescence quantum yields and remarkable solvatofluorochromic properties.
