Cyanomethyl anion transfer reagents for diastereoselective Corey–Chaykovsky cyclopropanation reactions
作者:Renè Hommelsheim、Katharina J. Hock、Christian Schumacher、Mohanad A. Hussein、Thanh V. Nguyen、Rene M. Koenigs
DOI:10.1039/c8cc05602a
日期:——
A readily available and bench-stable cyanomethyl sulfonium salt was used in highly diastereoselective Corey–Chaykovsky cyclopropanationreactions of electron-poor olefins. This efficient method provides a rapid route to access densely functionalized cyclopropyl nitriles.
The one-step preparation of 1-nitrobicyclo[3.1.0]hexane and bicycloisoxazoline-N-oxide was readily achieved from conjugate adducts of nitro alkenes and allylmalonates by treatment with Ag2O and iodine under basic conditions. We observed that when a primary alkyl group was present at the β-position of the nitro group, bicyclo[3.1.0]hexane was preferentially formed, whereas if a secondary alkyl group
Nucleophilic Difluoromethylation Using (Bromodifluoromethyl)trimethylsilane
作者:Alexey L. Trifonov、Artem A. Zemtsov、Vitalij V. Levin、Marina I. Struchkova、Alexander D. Dilman
DOI:10.1021/acs.orglett.6b01641
日期:2016.7.15
triphenylphosphine, and DMPU serves as a source of difluorinated phosphorus ylide Ph3P═CF2 under mild conditions. The system was used to effect nucleophilic difluoromethylation of ketones and nitro alkenes. The reaction efficiency is believed to be associated with Lewis acidic activation of the substrates by a silylium species formed upon generation of the phosphorus ylide.
Weak Lewis acid for high nucleophilicity: Hydridoborate derived from B(2,6‐F2C6H3)3 shows significant hydride character. Solid‐state and solution structure analysis revealed a dihydrogen‐bonded aggregate. The new frustratedLewispair was applied in the hydrogenation of nitroolefins and acrylates (see scheme; EWG=electron‐withdrawing group). The decreased Lewis acidity provides higher reactivity and
弱路易斯酸,具有高亲核性:衍生自B(2,6-F 2 C 6 H 3)3的氢硼酸盐显示出显着的氢化物特征。固态和溶液结构分析表明,存在氢键结合的聚集体。新的受阻的路易斯对用于硝基烯烃和丙烯酸酯的氢化反应(参见方案; EWG =吸电子基团)。降低的路易斯酸度可提供更高的反应性和官能团耐受性。
C3-Symmetric Proline-Functionalized Organocatalysts: Enantioselective Michael Addition Reactions
作者:Jarugu Narasimha Moorthy、Satyajit Saha
DOI:10.1002/ejoc.201000569
日期:2010.11
C 3 -Symmetric, tripodal catalyst 4 based on 1,3,5-triethylbenzene, which incorporates the features of a molecular receptor, is shown to catalyze Michaeladditionreactions of carbonyl compounds to β-nitrostyrenes in a high stereoselectivity (up to 99:1 dr and up to 98 % ee).
基于 1,3,5-三乙苯的 C 3 -对称三足催化剂 4 结合了分子受体的特征,显示出以高立体选择性(高达 99: 1 dr 和高达 98 % ee)。