共查询到20条相似文献,搜索用时 15 毫秒
1.
A stereoselective method has been developed for the synthesis of (Z)- and (E)-allyl iodides from Baylis-Hillman adducts using polymethylhydrosiloxane (PMHS) and iodine in chloroform at room temperature. In addition, the reagent system has been utilized for the iodination of benzylic alcohols selectively. 相似文献
2.
Biswanath Das Kongara Damodar Nisith Bhunia Boddu Shashikanth 《Tetrahedron letters》2009,50(18):2072-5609
Appel agents (PPh3/CBr4) have been utilized for high-yielding stereoselective synthesis of (Z)- and (E)-allyl bromides from Baylis-Hillman adducts at room temperature. The method has been applied for the synthesis of naturally occurring bioactive fatty acid amides, semiplenamides C and E. 相似文献
3.
Biswanath Das Joydeep Banerjee Anjoy Majhi Gurram Mahender 《Tetrahedron letters》2004,45(50):9225-9227
A convenient and facile stereoselective synthesis of (E)- and (Z)-trisubstituted alkenes has been achieved by treatment of unactivated Baylis-Hillman adducts with NaBH4 in the presence of CuCl2·2H2O at room temperature for 15 min. 相似文献
4.
A simple, mild and efficient stereoselective synthesis of (Z)- and (E)-allyl bromides and iodides has been developed by treatment of the Baylis-Hillman adducts with lithium bromide and iodide, respectively, in methylene chloride catalyzed by silica supported sodium hydrogen sulfate at room temperature. The role of various solvents, different reacting metallic halides, nature of the adducts and activity of several heterogeneous catalysts on the yields and stereochemistry of the products have been thoroughly studied. 相似文献
5.
Qibo Liu 《Journal of fluorine chemistry》2009,130(10):922-925
(E)-(1,2-Difluoro-1,2-ethenediyl)bis[tributylstannane], 3, readily undergoes a Pd(PPh3)4/CuI-catalyzed cross-coupling reaction with iodotrifluoroethene to yield (E)-octafluoro-1,3,5-hexatriene, 4, in high isomeric purity. (1Z,3E,5Z)-(1,2,3,4,5,6-Hexafluoro-1,3,5-hexenetriyl)bis[tributylstannane], 7, was sequentially prepared from (1Z,3E,5Z)-(1,2,3,4,5,6-hexafluoro-1,3,5-hexenetriyl)bis[triethylsilane], 5, which was prepared via a Pd(PPh3)4/CuI-catalyzed cross-coupling reaction of 3 with (E)-1,2-difluoro-1-iodo-2-triethylsilylethene, 6. Pd(PPh3)4/CuI cross-coupling of 7 with iodotrifluoroethene gave (3E,5E,7E)-dodecafluoro-1,3,5,7,9-decapentaene, 8. 相似文献
6.
Biswanath Das Nikhil Chowdhury Joydeep Banerjee Anjoy Majhi 《Tetrahedron letters》2006,47(37):6615-6618
An efficient one-pot stereoselective synthesis of trisubstituted (E)-2-methylalk-2-enoic acids has been accomplished by treatment of unactivated Baylis-Hillman adducts, 3-hydroxy-2-methylenealkanoates, with Al-NiCl2·6H2O in methanol at room temperature followed by hydrolysis. The method has been applied to the synthesis of three important insect pheromones, (4S,2E)-2,4-dimethyl-2-hexenoic acid, (+)-(S)-manicone and (+)-(S)-normanicone. 相似文献
7.
Biswanath Das Joydeep Banerjee Nasi Ravindranath Bollu Venkataiah 《Tetrahedron letters》2004,45(11):2425-2426
The stereoselective synthesis of (2Z)-2-(chloromethyl)alk-2-enoates has been achieved efficiently and in high yields and in short reaction times from Baylis-Hillman adducts, 3-hydroxy-2-methylene-alkanoates, by treatment with FeCl3 or InCl3 at room temperature. 相似文献
8.
Qibo Liu 《Journal of fluorine chemistry》2011,132(2):78-87
(Z)-HFCCFZnI was stereoselectively synthesized from activated zinc dust and (Z)-HFCCFI that was synthesized from chlorotrifluoroethene in a sequential manner. Compared to (E)-HFCCFZnI, (Z)-HFCCFZnI was more challenging to prepare in terms of sluggish metallation and formation of by-products, and underwent slower and incomplete Negishi coupling with aryl iodides. In a modification of Negishi coupling, (E)-α,β-difluorostyrenes were stereospecifically prepared in good to excellent yields under mild conditions from aryl iodides and (Z)-HFCCFZnI with the co-catalysis of Pd(PPh3)4/Cu(I)Br. Experimental investigation and mechanistic rationalization suggested that Cu(I)Br would be a scavenger of free ligands for the facilitation of Pd(PPh3)2 formation, and a supplier of ligand for the metathesis process. Alternatively, (Z)-HFCCFSnBu3 and aryl iodides with an electron-withdrawing group underwent Stille-Liebiskind coupling to afford (E)-α,β-difluorostyrenes. 相似文献
9.
Masanori Yoshida 《Journal of fluorine chemistry》2004,125(4):527-529
(Z)-β-Fluoro-α,β-unsaturated esters were stereoselectively synthesized from (Z)-2-fluoro-1-alkenyliodonium salts by the Pd-catalyzed methoxycarbonylation reaction. The reaction proceeded at room temperature and various functional groups on the substrate can tolerate the reaction conditions. 相似文献
10.
Yasser M.A. MohamedTrond Vidar Hansen 《Tetrahedron letters》2011,52(10):1057-1059
The first total synthesis of methyl (5Z,8Z,10E,12E,14Z)-eicosapentaenoate has been achieved in seven steps and in 16% overall yield. The synthesis confirmed the assigned structure of this polyunsaturated natural product. 相似文献
11.
Hydroindation of arylalkynylphosphonates gives a intermediate which can be hydrolyzed to (E)-2-arylvinylphosphonates in InCl3-NaBH4-MeCN system, the stereoselectivity and yield are rather high, but under the same conditions 2-alkylalkynylphosphonates do not react very well. 相似文献
12.
We report a highly efficient method for the synthesis of (Z)-3-ylidenephthalides via intramolecular cyclization of readily available 2-acyl-benzoic acids mediated by TSTU at room temperature. Using this method, diversely substituted (Z)-3-ylidenephthalides have been generated in good to excellent yields. The application of the method is highlighted by gram-scale preparation of the antiplatelet drug n-butylphthalide. 相似文献
13.
An improved synthesis of (2E,4Z)-6-(benzyloxy)-4-bromohexa-2,4-dien-1-ol has been devised. This new route increases the throughput and yield of the diene product by circumventing a low yielding preparation of boronic acid intermediate as well as removing the need to use multi-gram quantities of highly toxic thallium salts. In the process of developing this new route, a higher yielding preparation of (E)-3-hydroxyprop-1-enylboronic acid was also achieved. 相似文献
14.
The addition of several trialkyl or triarylindium reagents to the acetates of Baylis-Hillman adducts proceeds readily under the catalysis of copper and palladium derivatives. The reactions of trialkylindiums are catalyzed efficiently by CuI whereas additions of triarylindiums produce better results with Pd(PPh3)4. The reactions with 3-acetoxy-2-methylenealkanoates provide (E)-alkenes, whereas similar reactions with 3-acetoxy-2-methylenealkanenitriles lead to (Z)-alkenes. All the reactions are highly regio- and stereoselective and high yielding. 相似文献
15.
Kazuhiro Yoshizawa 《Tetrahedron》2007,63(27):6259-6286
Siloxyallenes proved to be a useful functional intermediate in the preparation of (Z)-β-branched Morita-Baylis-Hillman type adducts by the reaction of aldehydes with silylacetylenes or siloxypropynes. Various (Z)-chalcones were stereoselectively synthesized from siloxypropynes via siloxyallenes. 相似文献
16.
Various (Z)-chalcone derivatives were easily synthesized in a stereoselective manner from 1,3-diaryl-2-propynyl silyl ethers by a catalytic reaction using potassium tert-butoxide under very mild conditions after acid treatment. 相似文献
17.
The first time steroselective synthesis of (Z)-β-bromo Baylis-Hillman ketones has been achieved using a one-pot three-component reaction. The new system uses MgBr2 as both the Lewis acidic promoter and the bromine source for the Michael-type addition with α,β-acetylenic ketones to form an active β-bromo allenolate intermediate, which in turn attacks various aldehydes to afford β-bromo Baylis-Hillman adducts in good yields and Z-selectivity. 相似文献
18.
Chunguang Han 《Tetrahedron letters》2008,49(49):6988-6990
Secondary (E)-allyl vic-diol cleavage in the presence of the 2nd-generation Grubbs catalyst has been developed. The position of a vic-diol adjacent to CC plays a crucial role in the cleavage reaction compared to an alkyl vic-diol based on a model compound. 相似文献
19.
Takahiro Ichige 《Tetrahedron letters》2006,47(28):4843-4848
Both (E)- and (Z)-3-hydroxy-2-methyl-1-alkenyl iodides were stereoselectively synthesized from iodomethylated epoxides by treatment with sodium hexamethyldisilazane in DMF and with LDA in THF (or lithium 2,2,6,6-tetramethylpiperidide in THF), respectively. 相似文献
20.
Naïma Khiri 《Tetrahedron letters》2005,46(35):5807-5810
Enantiomerically pure (E)-β-sulfinylenones are smoothly prepared from β-ketoesters in three steps with good overall yield. Since they can be the substrates of many diastereoselective reactions, they represent versatile precursors of a wide range of chiral building blocks. We propose a rationale to explain the formation of (E)-β-sulfinylenones from the corresponding δ-enol-methylethers. 相似文献