排序方式: 共有44条查询结果,搜索用时 11 毫秒
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Pierre Thilmany Prof. Gwilherm Evano 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(1):248-252
An efficient and modular entry to α-halogenated amides and esters is reported. This reaction is based on an underestimated double electrophilic activation of ynamides sequentially involving highly reactive activated keteniminium and iminium ions. Upon simple reaction with HCl and an electrophilic halogenation reagent in the presence of water or an alcohol, a broad range of ynamides can be transformed, in a highly divergent manner, to α-halo amides and esters with high efficiency and under mild conditions. 相似文献
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Wen-Wen Zhang Su-Lei Zhang Bi-Jie Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(17):6941-6947
Chiral propargyl amines are valuable synthetic intermediates for the preparation of biologically active compounds and functionalized amines. Catalytic methods to access propargyl amines containing vicinal stereocenters with high diastereoselectivity are particularly rare. We report an unprecedented strategy for the synthesis of enantioenriched propargyl amines with two stereogenic centres. An iridium complex, ligated by a phosphoramidite ligand, catalyzes the hydroalkynylation of β,β-disubstituted enamides to afford propargyl amides in a highly regio-, diastereo-, and enantioselective fashion. Stereodivergent synthesis of all four possible stereoisomers was achieved using this strategy. 相似文献
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A simple and efficient synthesis of N-vinyl enamides via the lithiation and ring-opening reaction of 2-phenyl-2-oxazolines with lithium diisopropylamide at room temperature has been developed. This method is especially suitable for the synthesis of multifunctional enamides. Good yields have been obtained when the reactions were amplified to gram scale. 相似文献
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Congde Huo Lisheng KangXiaolan Xu Xiaodong JiaXicun Wang Haisheng XieYong Yuan 《Tetrahedron letters》2014
Commercially available stable radical cation triarylaminium salt can be used as an efficient initiator for Friedel–Crafts reaction of indoles with enamides to regioselectively construct complex indole derivatives and for double Friedel–Crafts reaction of indoles with vinyl ethers to offer 3,3′-Bis(indolyl)alkane derivatives. The ready availability of the starting materials and the usefulness of the products make this strategy attractive. 相似文献
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Piperazines and modified piperazines, such as homopiperazines and 2-methylpiperazines, are found in a wide range of pharmaceutical substances and biologically active molecules. In this study 2,5-diazabicyclo[4.1.0]heptanes, in which a cyclopropane ring is fused onto a piperazine ring, are described as modified piperazine analogues. Differentially N,N′-disubstituted and N-monosubstituted compounds can be readily prepared from 2-ketopiperazine in a few steps, using a Simmons-Smith reaction of 1,2,3,4-tetrahydropyrazines with diethylzinc and diiodomethane for the key cyclopropane ring formation. An analogue of the fluoroquinolone antibacterial Ciprofloxacin was synthesized using a palladium-catalyzed Buchwald-Hartwig cross-coupling to attach the diazabicyclo[4.1.0]heptane core to the 7-position of the fluoroquinolone core. The resultant analogue was demonstrated to have similar antibacterial activity to the parent drug Ciprofloxacin. X-ray crystallographic analysis of this analogue reveals a distorted piperazine ring in the diazabicyclo[4.1.0]heptane core. The pKa of the conjugate acid of N-Cbz-monoprotected 2,5-diazabicyclo[4.1.0]heptane was determined to be 6.74±0.05, which is 1.3 pKa units lower than the corresponding N-Cbz-monoprotected piperazine compound. The lower basicity of diazabicyclo[4.1.0]heptanes is due to the electron-withdrawing character of the adjacent cyclopropane rings. The modified physicochemical and structural properties of diazabicyclo[4.1.0]heptanes relative to piperazines are expected to lead to interesting changes in the pharmacokinetic and biological activity profile of these molecules. 相似文献
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Shuji Hirano 《Tetrahedron》2006,62(16):3896-3916
Aliphatic and aromatic sulfonamides were alkynylated with 1-bromo-1-alkynes in the catalytic presence of CuI to give N-(1-alkynyl)sulfonamides in good to excellent yields. Racemization of optically active sulfonamides was not observed during this alkynylation. The acetylene-titanium complexes generated from the resultant N-(1-alkynyl)sulfonamides and Ti(O-i-Pr)4/2 i-PrMgCl underwent regio-, olefinic stereo-, and diastereoselective addition to aldehydes to give virtually single allyl alcohols. Alternatively, inter- or intramolecular coupling reaction between N-(1-alkynyl)sulfonamides and another acetylene or olefin with the above titanium alkoxide reagent generated the corresponding titanacycles, hydrolysis of which furnished stereo-defined (sulfonylamino)dienes or cyclic compounds. 相似文献