Highly Diastereoselective Intermolecular β-Addition of Alkyl Radicals to Chiral 2-(Arylsulfinyl)-2-cycloalkenones
摘要:
The diastereoselectivity of intermolecular beta-addition of alkyl radicals to 2-(arylsulfinyl)-acycloalkenones depends largely upon the structure of the arylsulfinyl group. The reaction of a-cyclopentenones or 2-cyclohexenones having a sterically bulky arylsulfinyl group such as (3,5-di-tert-butyl-4-methoxyphenyl)-sulfinyl, (2,4,6-triisopropylphenyl)sulfinyl or (2,4,6-trimethylphenyl)-sulfinyl group gives 3-alkyl-2-(arylsulfinyl)-1-cyclopentanones or 3-alkyl-2-(arylsulfinyl)-1-cyclohexanones in excellent yields and with high diastereoselectivity. Both the X-ray crystallographic analysis and the NOE experiment in the H-1 NMR spectrum of (S)-2-[(2,4,6-triisopropylphenyl)-sulfinyl]- and (S)-2-[(2,4,6-trimethylphenyl)sulfinyl]-2-cyclopentenone reveal an effective shielding of one of the olefin faces at the beta-position by o-isopropyl and o-methyl groups. The addition of bidentate Lewis acids reverses the stereoselection through chelating the intermediates to give the addition products with high diastereoselectivity.
作者:Barbara J. Casavant、Azade S. Hosseini、Sherry R. Chemler
DOI:10.1002/adsc.201400317
日期:2014.8.11
carboamination reaction that creates bridged heterocycles is reported herein. Two new rings are formed in this alkene carboamination reaction where N-sulfonyl-2-aryl-4-pentenamines are converted to 6-azabicyclo[3.2.1]octanes using [Ph-Box-Cu](OTf)2 or related catalysts in the presence of MnO2 as stoichiometric oxidant in moderate to good yields and generally excellent enantioselectivities. Two new stereocenters
Mechanistic Analysis and Optimization of the Copper-Catalyzed Enantioselective Intramolecular Alkene Aminooxygenation
作者:Monissa C. Paderes、Jerome B. Keister、Sherry R. Chemler
DOI:10.1021/jo3023632
日期:2013.1.18
The catalytic asymmetric aminooxygenation of alkenes provides an efficient and straightforward approach to prepare chiral vicinal amino alcohols. We have reported a copper(II)-catalyzed enantioselective intramolecular alkene aminooxygenation, using (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) as the oxygen source, which results in the synthesis of chiral indolines and pyrrolidines. Herein we disclose
烯烃的催化不对称氨基氧化为制备手性邻氨基醇提供了一种有效且直接的方法。我们报道了铜 (II) 催化的对映选择性分子内烯烃氨基氧化,使用 (2,2,6,6-四甲基哌啶-1-基) 氧基 (TEMPO) 作为氧源,从而合成手性二氢吲哚和吡咯烷. 在此,我们公开了动力学研究表明反应在底物和 [Cu( R,R )-Ph-双(恶唑啉)]OTf 2催化剂中都是一级反应,而在 TEMPO 中是零级反应。此外,动力学同位素效应研究支持顺式-氨基铜化步骤,即在烯烃上添加 N-Cu,是限速步骤。如氘标记实验所示,随后形成碳自由基中间体和用 TEMPO 直接捕获碳自由基是 C-O 键形成的指示机制。配体屏幕显示双(恶唑啉) 上的C(4)-苯基取代是高不对称诱导的最佳选择。底物N-磺酰基的大小也影响反应的对映选择性。证明了制备规模的催化氨基氧化反应(克规模),并且在更大规模的反应中发现了对反应温度的意外依赖性。
An improved and efficient procedure for the preparation of chiral sulfinates from sulfonyl chloride using triphenylphosphine
An improvedprocedure of the Sharpless method for the preparation of chiral sulfinates by triphenylphosphine is described. A mixture of sulfonyl chlorides and diacetone-d-glucose or l-menthol in the presence of triethylamine was treated with triphenylphosphine in CH2Cl2 at 0°C to give the sulfinates in good yields.
We disclose here a novel electrophilic fluorinating reagent, N-fluoro-(3,5-di-tert-butyl-4-methoxy)benzenesulfonimide (NFBSI) as a sterically demanding analogue of popular fluorinating reagent, N-fluorobenzenesulfonmide (NFSI). NFBSI improves the enantioselectivity of the products as much as 18% for the cinchona alkaloid-catalyzed enantioselectivefluorination of silylenol ether compared to the use
Amphipathic sulfonamidobenzamides mimicking small antimicrobial marine natural products; investigation of antibacterial and anti-biofilm activity against antibiotic resistant clinical isolates
作者:Elizaveta M. Igumnova、Ekaterina Mishchenko、Tor Haug、Hans-Matti Blencke、Johanna U. Ericson Sollid、Elizabeth G. Aarag Fredheim、Silje Lauksund、Klara Stensvåg、Morten B. Strøm
DOI:10.1016/j.bmc.2018.08.032
日期:2018.9
There is an urgent need for novel antimicrobial agents to address the threat of bacterial resistance to modern society. We have used a structural motif found in antimicrobial marine hit compounds as a basis for synthesizing a library of antimicrobial sulfonamidobenzamide lead compounds. Potent in vitro antimicrobial activity against clinically relevant bacterial strains was demonstrated for two compounds, G6 and J18, with minimal inhibitory concentrations (MIC) of 4-16 mu g/ml against clinical methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VRE). The two compounds G6 and J18, together with several other compounds of this library, also caused >= 90% eradication of pre-established biofilm of methicillin-resistant S. epidermidis (MRSE) at 40 mu g/ml. Using a luciferase assay, the mechanism of action of G6 was shown to resemble the biocide chlorhexidine by targeting the bacterial cell membrane.