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91.
Normal‐to‐Abnormal NHC Rearrangement of AlIII,GaIII, and InIII Trialkyl Complexes: Scope,Mechanism, Reactivity Studies,and H2 Activation 下载免费PDF全文
Dr. Gilles Schnee Prof. Olalla Nieto Faza Dr. David Specklin Dr. Béatrice Jacques Dr. Lydia Karmazin Prof. Richard Welter Prof. Carlos Silva López Dr. Samuel Dagorne 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(49):17959-17972
The present contribution reports experimental and theoretical mechanistic investigations on a normal‐to‐abnormal (C2‐to‐C4‐bonded) NHC rearrangement processes occurring with bulky group 13 metal NHC adducts, including the scope of such a reactivity for Al compounds. The sterically congested adducts (nItBu)MMe3 (nItBu=1,3‐di‐tert‐butylimidazol‐2‐ylidene; M=Al, Ga, In; 1 a – c ) readily rearrange to quantitatively afford the corresponding C4‐bonded complexes (aItBu)MMe3 ( 4 a – c ), a reaction that may be promoted by THF. Thorough experimental data and DFT calculations were performed on the nNHC‐to‐aNHC process converting the Al‐nNHC ( 1 a ) to its aNHC analogue 4 a . A nItBu/aItBu isomerization is proposed to account for the formation of the thermodynamic product 4 a through reaction of transient aItBu with THF–AlMe3. The reaction of benzophenone with (nItBu)AlMe3 afforded the zwitterionic species (aItBu)(CPh2‐O‐AlMe3) ( 6 ), reflecting the unusual reactivity that such bulky adducts may display. Interestingly, the nItBu/Al(iBu)3 Lewis pair behaves like a frustrated Lewis pair (FLP) since it readily reacts with H2 under mild conditions. This may open the way to future reactivity developments involving commonly used trialkylaluminum precursors. 相似文献
92.
Silvère André Lydia Saint Cristau Sabine Gaillard Olivier Devos Éric Calvosa Ludovic Duponchel 《Analytica chimica acta》2015
The Food and Drug Administration's (FDA) process analytical technology (PAT) framework has been initiated to encourage drug manufacturers to develop innovative techniques in order to better understand their processes and institute high level quality control which allows action at any point in the manufacturing process. While Raman spectroscopy and chemometrics have been successfully used to predict concentration of conventional metabolites in cell cultures, it is really not the case for active substances. Thus, we propose, for the first time, an in-line and real-time prediction of recombinant antibody titer using an immersion probe link to a spectrometer without the tacking of samples. A good robustness of the method is observed on different culture batches and the contamination risk is drastically reduced which is an important issue in biotechnology manufacturing processes. 相似文献
93.
Andrea C. Bruttomesso Javier Eiras Javier A. Ramírez Lydia R. Galagovsky 《Tetrahedron letters》2009,50(28):4022-4024
In this Letter we report that the Ugi reaction/cyclization sequence on a steroidal 17-carboxaldehyde leads to novel steroidal 2,5-diketopiperazines with a noteworthy stereoselectivity. A wide variety in the substitution pattern in the heterocyclic moiety was easily achieved by changing the components in the Ugi reaction. 相似文献
94.
Lydia Ajayi Ademola Ayeleso Temitope Oyedepo Emmanuel Mukwevho 《Molecules (Basel, Switzerland)》2021,26(11)
Background: There is an increasing need for botanicals to be used as an alternative and complementary medicine in the management of male infertility. Male infertility has been a major health/social challenge to people all over the world. This study, therefore, investigated the ameliorative potential of hydroethanolic leaf extract of Parquetina nigrescens (HELEPN) against d-galactose-induced testicular injury. Methods: Thirty male Wistar rats were randomly allotted into six groups (n = 5). Group I (Normal control), Group II (300 mg/kg b.w. d-galactose), Group III and IV (250 and 500 mg/kg b.w. HELEPN, respectively), Group V and VI (both received 300 mg/kg b.w. of d-galactose with 250 and 500 mg/kg b.w of HELEPN, respectively). d-galactose administration started two weeks prior to HELEPN treatment which lasted for six weeks. All assays were carried out using established protocols. Results: Administration of HELEPN at 250mg/kg and 500mg/kg concomitantly with d-galactose improved paired and relative testicular weights, levels of gonadotropins (LH and FSH) and testosterone, and poor sperm quality. HELEPN treatment reduced the levels of oxidative stress biomarkers (MDA, 8-OHDG, and AGEs) and inflammatory response (TNF-alpha and NO) to normal, as well as restoring the reduced activities of antioxidant enzymes (glutathione peroxidase, superoxide dismutase, and catalase). In addition, HELEPN treatment mitigated testicular DNA fragmentation and down-regulated caspase 3-activities. HELEPN at 500 mg/kg was observed to have the greatest ameliorative effect. Conclusion: HELEPN protects against d-galactose-induced testicular injury through antioxidative, anti-inflammatory, and antiapoptotic mechanisms. 相似文献
95.
Lydia N. Raser Stephen V. Kolaczkowski Therese M. Cotton 《Photochemistry and photobiology》1992,56(2):157-162
Hypericin has been found to exhibit a variety of photodynamic effects. To correlate biological activity with molecular structure, complete physical characterization of hypericin is required. The vibrational spectrum has been determined and resonance Raman and surface enhanced resonance Raman scattering spectra are reported. In addition, the Raman spectrum of a model compound has been studied to facilitate assignment of the vibrational modes of hypericin. 相似文献
96.
John J. D'Amico Lydia Suba Peter G. Ruminski 《Journal of heterocyclic chemistry》1986,23(6):1629-1635
The reaction of 2-mercaptobenzothiazole, 2-mercaptobenzoxazole or 5-chloro-2-mercaptobenzothiazole with either acrylonitrile or acrylamide under basic conditions afforded the N-cyanoethylated products 1, 2 and 3 or the N-amidoethylated products 4, 5 and 6 , respectively. The reaction of the sodium salts of the same thiazolethiols with 3-chloropropionitrile furnished a mixture containing the N-cyanoethylated products 1, 2 and 3 and the unknown S-cyanoethylated products 7, 8 and 9 , respectively. Whereas, substituting 3-chloropropionamide for 3- chloropropionitrile in the same reaction gave only the S-substituted products 10, 11 , and 12 , respectively. The treatment of 10, 11 or 12 with phosphorus oxychloride or thionyl chloride in DMF afforded 7, 8 and 9 in excellent yields. Possible mechanisms and supporting nmr data are discussed. 相似文献
97.
Manuel Soriano-García Baldomero Esquivel Rubén Toscano Luis Estebanes Lydia Rodríguez-Hahn 《Journal of chemical crystallography》1987,17(6):761-770
The title compound is C19H18O4·1/2 CH3OH, triclinic,P¯1,a=9.891(2),b=13.273(4),c=13.860(4) Å,a=66.47(2),=86.91(2), and =85.59(2)°. The structure was solved by direct methods and refined by least-squares techniques to anR factor of 0.082 for 2282 observed reflections. The X-ray structure uniquely resolves the one remaining ambiguity, namely the assignment of the correct structure4. There are two crystallographically independent molecules (A and B) and one disordered methanol molecule. Both molecular skeletons show small distortions from planarity with inclinations of 1.7 and 4.0° between the outermost rings A/C in molecules A and B, respectively. Intramolecular hydrogen bonds of the form O(3A)-HO(2A) and O(3B)-HO(2B) are observed in molecules A and B, respectively. The molecules are linked by pairs of O(3A)-HO(2B) and O(3B)-HO(2A) hydrogen bonds. The dimerlike structures are stabilized by intermolecular C-HO interactions and van der Waals forces. 相似文献
98.
Lydia KerschensteinerFlorian Löbermann Wolfgang Steglich Dirk Trauner 《Tetrahedron》2011,67(8):1536-1539
Crocipodin, an unusual benzotropolone pigment, has been isolated from the fruit bodies of the mushroom Leccinum crocipodium. Its structure was determined by spectroscopic methods, particularly 2D NMR spectroscopy. The structure was confirmed by total synthesis, starting from 4-bromocatechol and gallic acid. 相似文献
99.
100.