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31.
Asymmetric Catalytic Preparation of Polysubstituted Cyclopropanol and Cyclopropylamine Derivatives
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Marwan Simaan Prof. Dr. Ilan Marek 《Angewandte Chemie (International ed. in English)》2018,57(6):1543-1546
The catalytic asymmetric carbometalation of cyclopropenes followed by either an electrophilic oxidation or amination reaction provides a unique approach to the formation of diastereomerically pure and enantiomerically enriched cyclopropanol and cyclopropylamine derivatives, respectively. 相似文献
32.
33.
Cohen T Gibney H Ivanov R Yeh EA Marek I Curran DP 《Journal of the American Chemical Society》2007,129(49):15405-15409
The cyclizations of a number of terminally unsaturated alkenyl zinc iodides to cyclopentylmethylzinc iodides, formerly believed to be nonradical in nature, have been revealed as radical chain cyclizations initiated by adventitious oxygen. Five cases are presented in which the published carbozincation cis/trans selectivities are essentially the same as those found for the cyclizations of the unsaturated alkyl iodide precursors of the alkylzinc iodides by the iodine atom transfer method at approximately the same temperatures. In addition, it has been found that one of the organozinc cyclizations does not occur in a system in which oxygen has been rigorously excluded. The combined findings strongly suggest that these organozinc cyclizations occur by a zinc radical transfer mechanism rather than by a conventional carbometallation that is thought to occur with the analogous organolithium and organomagnesium cyclizations. 相似文献
34.
Vocal fold polyps are typically caused by acute and chronic trauma to the microvasculature of the superficial lamina propria (SLP). Shearing stresses that are induced by hyperfunctional glottal sound production lead to bleeding into the SLP and malformed neo-vascularized masses. Because the primary process does not involve the epithelium, the authors designed a technique to resect hemorrhagic polyps by epithelial cordotomy with partial or complete preservation of the vocal fold epithelium. This approach is different from the traditional microsurgical resection of hemorrhagic polyps by amputation with or without the carbon dioxide laser. Forty patients who underwent microlaryngoscopic resection of hemorrhagic polyps from 1996 through 1998 were reviewed retrospectively. Thirty-six of the 40 procedures were by epithelial cordotomy and subepithelial removal of the polyp contents. Sixteen of 36 were assisted by a subepithelial infusion of saline and epinephrine, and all were 3 mm to 6 mm. Four of 40 polyps were amputated; all of these were less than 3 mm and were pedicled on a narrow base. Cold instruments were used exclusively in all 40 patients. Postoperative laryngeal stroboscopy within 2 weeks revealed improved mucosal wave propagation and improved glottal closure in all 33 patients in whom postoperative strobovideolaryngoscopy was available. The epithelial cordotomy technique was introduced to minimize disturbance of normal SLP and epithelium. Despite the hemorrhagic nature of these lesions, cold instruments could be used exclusively with facility due to careful microdissection between the polyp and the residual normal SLP and the enhanced hemostasis provided by the subepithelial infusion of saline and epinephrine. The rapid return to improved glottal function is the result of this ultra tissue-sparing technique. 相似文献
35.
Paul Michael Tessler Moshe Friedman Moshe Halfon Shlomi Palchan Tala Weissman Leonid Arenshtam Alexander Berkovits Dan Eisen Yosef Eliahu Ilan Feinberg Gitai Kijel Daniel Kreisel Arik Mardor Israel Shimel Guy Shor Asher Silverman Ido 《The European Physical Journal A - Hadrons and Nuclei》2019,55(3):1-10
The European Physical Journal A - An empirical formula is proposed for the two-proton decay half-lives. This study is an extension of the empirical formula reported recently by us for calculating... 相似文献
36.
Overcoming the inherent difficulty to prepare quaternary carbon stereogenic centers, the diastereo‐ and enantioselective preparation of acyclic carbon backbones possessing vicinal quaternary and tertiary stereogenic centers (i.e. in a 1,2‐relationship) causes distorted geometries and represents a very acute problem in organic synthesis. Several approaches are discussed in this minireview underlining the challenges illustrated by the rather limited number of approaches available to practitioners. 相似文献
37.
Ilan Zisser 《Archiv der Mathematik》1991,57(2):109-113
The content of this paper corresponds to a part of the author's Ph.D. thesis carried out in Tel Aviv University under the supervision of Prof. Marcel Herzog. 相似文献
38.
Ilan Benjamin 《Chemical physics》1994,180(2-3):287-296
The dynamics of solvent reorganization following charge transfer at the interface between two immiscible liquids, one polar and the other non-polar are investigated by molecular dynamics. Both charge separation and charge recombination processes in two different orientations at the surface are considered and are compared with the same processes in the bulk polar solvent. The relaxation at the surface is significantly slower than in the bulk, in contrast to predictions of continuum models. The linear response approximation works reasonably well in the bulk but fails at the interface. The Langevin model is in poor agreement with the exact equilibrium correlations, especially at short time, but can qualitatively account for the overall rate. 相似文献
39.
We consider the continuous trajectories of the vector field induced by the primal affine scaling algorithm as applied to linear programming problems in standard form. By characterizing these trajectories as solutions of certain parametrized logarithmic barrier families of problems, we show that these trajectories tend to an optimal solution which in general depends on the starting point. By considering the trajectories that arise from the Lagrangian multipliers of the above mentioned logarithmic barrier families of problems, we show that the trajectories of the dual estimates associated with the affine scaling trajectories converge to the so called centered optimal solution of the dual problem. We also present results related to asymptotic direction of the affine scaling trajectories. We briefly discuss how to apply our results to linear programs formulated in formats different from the standard form. Finally, we extend the results to the primal-dual affine scaling algorithm. 相似文献
40.
Kihong Lee Bonnie Choi Dr. Ilan Jen‐La Plante Maria V. Paley Xinjue Zhong Prof. Andrew C. Crowther Prof. Jonathan S. Owen Prof. Xiaoyang Zhu Prof. Xavier Roy 《Angewandte Chemie (International ed. in English)》2018,57(21):6125-6129
Two‐dimensional (2D) materials are commonly prepared by exfoliating bulk layered van der Waals crystals. The creation of synthetic 2D materials from bottom‐up methods is an important challenge as their structural flexibility will enable chemists to tune the materials properties. A 2D material was assembled using C60 as a polymerizable monomer. The C60 building blocks are first assembled into a layered solid using a molecular cluster as structure director. The resulting hierarchical crystal is used as a template to polymerize its C60 monolayers, which can be exfoliated down to 2D crystalline nanosheets. Derived from the parent template, the 2D structure is composed of a layer of inorganic cluster, sandwiched between two monolayers of polymerized C60. The nanosheets can be transferred onto solid substrates and depolymerized by heating. Electronic absorption spectroscopy reveals an optical gap of 0.25 eV, narrower than that of the bulk parent crystalline solid. 相似文献