Stereospecific Palladium-Catalyzed Cross-Coupling of (<i>E</i>)- and (<i>Z</i>)-Alkenylsilanolates with Aryl Chlorides
作者:Scott E. Denmark、Jeffrey M. Kallemeyn
DOI:10.1021/ja065988x
日期:2006.12.1
geometrically defined (E)- and (Z)-alkenyl- and styrylsilanolates with a wide variety of aromatic and heteroaromatic chlorides has been achieved. Under catalysis by bulky, biphenyl-derived phosphines and allylpalladium chloride, the (preformed, stable) potassium salts of di-, tri- and tetrasubstituted alkenyldimethylsilanols undergo high yielding and highly stereospecific coupling to aryl chlorides in THF or dioxane
Catalyst-controlled reverse selectivity in C–C bond formation: NHC-Cu-catalyzed α-selective allylic alkylation with organolithium reagents
作者:Stefano F. Pizzolato、Massimo Giannerini、Pieter H. Bos、Martín Fañanás-Mastral、Ben L. Feringa
DOI:10.1039/c5cc01521a
日期:——
An efficient and highly [small alpha]-selective copper-catalyzed allylic alkylation of allylic halides with organolithium reagents is presented. The use of N-heterocyclic carbenes as ligands is key to reverse the common [small alpha]-selectivity...
Cross-coupling reactions of alkenylsilanols with fluoroalkylsulfonates: development and optimization of a mild and stereospecific coupling process
作者:Scott E. Denmark、Christopher S. Regens
DOI:10.1016/j.tetlet.2010.11.133
日期:2011.4
The development of an effective protocol for the palladium-catalyzed cross-coupling of (E)-alkenylsilanols with aryl triflates is described. A critical component in the optimization of this method was balancing the stability and reactivity of the triflates in the presence of a nucleophilic promoter. This report highlights the use of a slightly soluble Brønsted base promoter that allows for a low, steady-state
描述了钯催化 ( E )-烯基硅烷醇与芳基三氟甲磺酸酯交叉偶联的有效方案的开发。优化该方法的一个关键组成部分是在亲核启动子的存在下平衡三氟甲磺酸酯的稳定性和反应性。本报告重点介绍了使用微溶的 Brønsted 碱促进剂,它允许溶液中烯基(二甲基)硅烷醇化物的低、稳态浓度,从而促进交叉偶联,而不是三氟甲磺酸酯的 S-O 键断裂。
Highly Stereoselective Hydrocarbation of Terminal Alkynes via Pt-Catalyzed Hydrosilylation/Pd-Catalyzed Cross-Coupling Reactions
作者:Scott E. Denmark、Zhigang Wang
DOI:10.1021/ol0156751
日期:2001.4.1
[GRAPHICS]The formal addition of an aryl-H or alkenyl-H bond across a terminal alkyne has been accomplished by the combination of platinum-catalyzed hydrosilylation followed by palladium-catalyzed cross-coupling, The use of the t-Bu3P-Pt(DVDS) catalyst in combination with tetramethyldisiloxane gave excellent regio- and stereoselectivity with a number of alkyne substrates, Subsequent, fluoride-promoted cross-coupling proceeded in high yield and stereospecificity for a variety of aryl halides.
Antifungal Pharmacodynamic Characteristics of Amphotericin B against<i>Trichosporon asahii</i>, Using Time-Kill Methodology
AbstractWe determined the MIC of amphotericin B against 45 Trichosporon asahii isolates from various clinical and environmental sources, and used in vitro time‐kill methods to characterize the relationship between amphotericin B concentrations and MIC for four representative T. asahii isolates. Amphotericin B had concentration‐dependent antifungal activity. MICs ranged from 0.5 to 16 μg/ml, and most T. asahii isolates (76%, 34/45) were inhibited at safely achievable amphotericin B serum concentrations (≤ 2 μg/ml). However, 40% (18/45) of isolates were not killed at these concentrations (MFCs from 1.0 to 32 μg/ml). At concentrations ≥ 2 × MIC, amphotericin B exhibited fungicidal activity (< 99.9% reduction in CFU) over a 12‐hr time‐period; the maximal effect was achieved at ≥ 4 × MIC. Susceptibility testing confirmed the resistance of T. asahii to amphotericin B, and in vitro pharmacodynamic results also suggest that amphotericin B is not suitable therapy for T. asahii infection.