共查询到20条相似文献,搜索用时 15 毫秒
1.
Zheng-Wang Chen Dong-Nai Ye Min YeZhong-Gao Zhou Shen-Huan LiLiang-Xian Liu 《Tetrahedron letters》2014
A AgF/TFA-promoted highly efficient synthesis of a wide range of α-haloketones from haloalkynes is described. The reactions are conducted under convenient conditions and provide products in moderate to excellent yields, with broad substrate scope, including a variety of aromatic chloroalkynes and bromoalkynes. 相似文献
2.
An asymmetric Michael-type reaction of phosphorus ylides and α,β-unsaturated ketones under the catalysis of a chiral ion pair catalyst has been described. The ion pair catalyst containing a chiral counteranion was prepared by simply mixing 9-amino-(9-deoxy)-epi-quinine with l-N-Boc-proline. The optically active α-methylene-δ-ketoesters could be obtained with good to excellent enantioselectivities (up to 95% ee) under mild reaction conditions. 相似文献
3.
The development of axially chiral dicarboxylic acid catalyzed desymmetrizing asymmetric semipinacol rearrangement of symmetrically substituted six-membered cyclic β-hydroxy-α-diazo esters is reported as a means to give chiral cycloheptanones with good enantioselectivities. 相似文献
4.
Dae Young Kim 《合成通讯》2013,43(17):2203-2209
A simple and practical strategy to access β-selenated cyclic ketone derivatives through the catalyst-free selenylation and semipinacol rearrangement sequence of 1-(1-arylvinyl)cyclobutanols was developed. This reaction employs the easily accessible and shelf-stable benzeneselenyl bromide as an electrophilic selenium source, and the reaction has advantages of mild reaction conditions and broad substrate scope. 相似文献
5.
《Tetrahedron: Asymmetry》1999,10(17):3417-3430
A very efficient and straightforward synthesis of novel chiral α-acetylenic ketones of type 3 has been developed. Starting from commercially available l-(−)-serine 4, and through the Garner's aldehyde 5, ethynyloxazolidine 2 was formed in good overall yield. Condensation of the corresponding lithium acetylide 7 with different aliphatic and aromatic aldehydes 5 and 8a–h at low temperatures yielded the respective propargylic alcohols 9a–i. Subsequent mild oxidation of 9a–i with 10-I-4-iodinane oxide (IBX) 12 afforded chiral α-acetylenic ketones 3a–i almost quantitatively. 相似文献
6.
Sandeep Goyal Anang Pal Mangilal Chouhan Mukesh Gangar Sharad Sarak Vipin A. Nair 《Tetrahedron letters》2017,58(4):346-348
An efficient strategy for a one-pot, single step synthesis of β-lactams employing an imidazolidinone based chiral auxiliary with various aldimines via asymmetric Mannich-type reaction has been described. 相似文献
7.
Seyed Mohammad Vahdat Robabeh Baharfar Akbar Heydari Samad Khaksar 《Tetrahedron letters》2008,49(46):6501-6504
A new and highly flexible procedure is described for the synthesis of α-amino- and α-hydroxy phosphonates. In the presence of a catalytic amount of oxalic acid (10 mol %), trimethyl phosphite reacts with aldehydes or imines (generated in situ from an aldehyde and an amine) to yield the corresponding coupled products in good yield. 相似文献
8.
Kawai H Okusu S Tokunaga E Sato H Shiro M Shibata N 《Angewandte Chemie (International ed. in English)》2012,51(20):4959-4962
Ether way: the cinchona-alkaloid-catalyzed title reaction was achieved in high yields with high to excellent ee values for the first time, and affords key intermediates for the biologically important 2 having a trifluoromethylated all-carbon quaternary chiral center. Ether-type catalysts (1) are more efficient in this transformation than the conventional hydroxy analogues. 相似文献
9.
An efficient direct asymmetric aldol reaction between hydroxyacetone and β,γ-unsaturated α-keto esters has been successfully developed. In the presence of 9-amino-9-deoxy-epi-cinchonine and trifluoroacetic acid, the direct aldol reaction of O-protected hydroxyacetone proceeded in a highly enantioselective manner, affording the desired adducts containing a chiral tertiary alcohol in high yields and with excellent enantioselectivities. The aldol products obtained are valuable precursors for the synthesis of 2-substituted glycerol derivatives. 相似文献
10.
Li W Liu X Hao X Cai Y Lin L Feng X 《Angewandte Chemie (International ed. in English)》2012,51(34):8644-8647
Asymmetric expansion: A catalytic asymmetric ring-expansion reaction of the title compounds occurs in the presence of a Sc(OTf)(3) catalyst bearing an N,N'-dioxide-based ligand. Highly functionalized 2-quinolone derivatives containing a chiral C4-quaternary stereocenter were obtained in high yields and high levels of selectivity under mild reaction conditions (see scheme; Tf=trifluoromethanesulfonyl). 相似文献
11.
Zheng-Chao Duan Xiang-Ping Hu Dao-Yong Wang Sai-Bo Yu Zhuo Zheng 《Tetrahedron letters》2009,50(48):6720-2164
A series of chiral alkylphosphonates bearing β-stereogenic center were synthesized in good enantioselectivities (up to 95% ee) via the CuH-catalyzed asymmetric conjugate reduction of β-substituted α,β-unsaturated phosphonates under optimal conditions using Cu(OAc)2·H2O as the copper source, (R)-SEGPHOS as the ligand, PMHS as the siloxane, and t-BuOH as the additive. 相似文献
12.
Electrochemical oxidative radical sulfonylation/semipinacol rearrangement sequences of alkenylcyclobutanols have been developed. The reaction proceeds in an undivided electrochemical cell equipped with platinum plate electrodes employing sodium iodide as a redox catalyst and a supporting electrolyte. This approach is environmentally benign by using shelf-stable arylsulfonyl hydrazides as arylsulfonyl radical precursor and electrons as oxidizing reagents. The present protocol offers a facile way to prepare β-sulfonated cyclic ketone derivatives. 相似文献
13.
Chunhai Wang Xiaoling Huang Xueting Liu Suqian Gao Bin Zhao Shangdong Yang 《中国化学快报》2020,31(3):677-680
Hydroxyphosphoric acids display the unique biological activities,and they have some attractive prospects as clinical drug moleculars.Herein,a new approach for the synthesis ofγ-oxo-phosphonates(the precursor of hydroxyphosphoric acid)has been established through the semipinacol rearrangement tactic involved the photo-induced phosphorus radical process.Most important,this transformation is avoid of the external oxidants,and occurs very well under the sunlight irradiation,meanwhile theγ-oxo-phosphonate was easily derivatized to obtainγ-hydroxyphosphoric acid,thus highlights the synthesis value of this method. 相似文献
14.
Organocatalytic α-amination-allylation-RCM strategy: enantioselective synthesis of cyclic hydrazines
Aram Lim 《Tetrahedron letters》2008,49(33):4882-4885
A highly enantioselective method for the synthesis of cyclic hydrazines by using organocatalytic α-amination-allylation-RCM strategy is described. Proline-catalyzed α-amination of aldehydes followed by indium-mediated one-pot allylation of the crude α-hydrazino aldehydes produces 1,2-aminoalcohols in high enantio- and diastereoselectivities. The 1,2-aminoalcohols are further converted into cyclic hydrazines by using ring-closing metathesis (RCM) reaction. 相似文献
15.
An efficient rhodium-catalyzed synthesis of 2H-azirines and pyrroles has been developed. Novel rearrangement of α-oximino ketenes derived from α-diazo oxime ethers provides 2H-azirines bearing quaternary centers and allows for subsequent rearrangement to highly substituted pyrroles in excellent yields. 相似文献
16.
Minoru Ozeki Honoka Egawa Toshiki Takano Hideki Mizutani Narumi Yasuda Kenji Arimitsu Tetsuya Kajimoto Shinzo Hosoi Hiroki Iwasaki Naoto Kojima Manabu Node Masayuki Yamashita 《Tetrahedron》2017,73(15):2014-2021
A practical method for the synthesis of chiral β2,3-amino esters having various substituents was developed, which is characterized by an asymmetric Michael addition reaction of a chiral lithium amide with trisubstituted (E)-α,β-unsaturated esters. We found that a highly face-selective protonation occurred by the quick addition of water to the enolate intermediate derived from the Michael addition reaction to afford N-protected β2,3-amino esters in moderate to excellent yields. This finding was made possible by the facile preparation of geometrically pure trisubstituted (E)-α,β-unsaturated esters, which was established recently by our group. The subsequent deprotection of the amino group in the Michael adduct by using N-iodosuccinimide (NIS) efficiently provided β2,3-amino esters having various substituents. 相似文献
17.
Ying-Ying Peng Peng Liu Zhen-Jiang Liu Jin-Tao Liu Hai-Fang Mao Yue-Liang Yao 《Tetrahedron》2018,74(24):3074-3080
Highly regio- and diastereoselective Reformatsky reaction of stable, chiral fluoroalkyl α,β-unsaturated N-tert-butanesulfinyl ketimines was developed, which provided an efficient method for the asymmetric synthesis of structurally diverse β-tetrasubstituted β-fluoroalkyl β-vinyl β-amino esters in good yields and with excellent diastereoselectivities (dr up to 96:4). 相似文献
18.
《Tetrahedron: Asymmetry》2014,25(2):156-162
Herein we report a practical and efficient method for the synthesis of optically active 2,4-disubstituted oxazolines (S)-1a–h in good to excellent yields. The target compounds were prepared in good yield through the Horner–Wadsworth–Emmons reaction of β-phosphonoamide 3 bearing l-phenylalaninol with commercially available aryl aldehydes followed by the cyclodehydration of the corresponding N-(cinnamoyl)-(S)-phenylalaninol derivatives (S)-2a–h. Additionally, the cyclodehydration of β-phosphonoamide (S)-3 followed by the Horner–Wadsworth–Emmons reaction of β-phosphono-oxazoline (S)-4 with aryl aldehydes also gave the 2,4-disubstituted oxazolines (S)-1a–h. 相似文献
19.
20.
Jan Vesely 《Tetrahedron letters》2008,49(27):4209-4212
A novel organocatalytic highly enantioselective nitrocyclopropanation reaction of α,β-unsaturated aldehydes is presented. The 1-nitro-2-formylcyclopropane derivatives synthesized from this catalytic transformation were converted to the corresponding β-nitromethyl-acid esters, which are excellent precursors of GABA analogues such as Baclofen, by subsequent organocatalytic chemoselective ring-opening. 相似文献