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1.
Vo D.M. Hoang 《Tetrahedron letters》2007,48(45):8014-8017
Chiral (iminophosphoranyl)ferrocenes (1 and 2) are highly efficient ligands to achieve high diastereoselectivity (up to 95/5 dr in favor of the cis-isomer) as well as enantioselectivity (up to 99% ee) in Ru-catalyzed asymmetric cyclopropanation of various olefins. Reversal in diastereoselectivity is found as a function of metal-to-ligand ratio in the reaction of styrene. 相似文献
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J Li SH Liao H Xiong YY Zhou XL Sun Y Zhang XG Zhou Y Tang 《Angewandte Chemie (International ed. in English)》2012,51(35):8838-8841
A helping hand: A series of bis(oxazoline) ligands, which contain pendant C(2) -symmetry-breaking groups, for the Cu-catalyzed asymmetric cyclopropanation of 1,2-disubstituted alkenes has been developed. Under mild reaction conditions, both cis- and trans-1,2-substituted alkenes can be converted into the corresponding 1,2,3-trisubstituted cyclopropanes with high levels of diastereo- and enantioselectivity. 相似文献
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Catalytic asymmetric allylic oxidation of cyclic olefins ocurrs for the first time in very high (94-99% ee) enantioselectivity using copper(I) complexes of malonyl derived bisoxazolines and tert-butyl p-nitroperbenzoate giving allyl benzoates in moderate yield. The copper complex, 15 mol %, was used in acetonitrile at -20 degrees C over an extended period, 5-12 d, with excess olefin together with one equivalent of perester. The S-esters were generated in accord with the model proposed previously for the (S,S)-bisoxazoline ligand. An eta2 intermediate was ruled out using low-temperature 13C NMR with the complex in the presence of olefin. 相似文献
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This paper describes a promising asymmetric cyclopropanation system for unfunctionalized olefins using readily available dipeptide N-Boc-l-Val-l-Pro-OMe as ligand. 相似文献
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Jiang Long 《Tetrahedron letters》2005,46(16):2737-2740
This paper describes a catalytic asymmetric cyclopropanation system for unfunctionalized olefins using readily available dipeptide N-Boc-l-Val-l-Pro-OMe (1) as ligand. 相似文献
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Chanthamath S Phomkeona K Shibatomi K Iwasa S 《Chemical communications (Cambridge, England)》2012,48(62):7750-7752
The Ru(II)-Pheox complex is an efficient catalyst for the intermolecular cyclopropanation of various terminal olefins with succinimidyl diazoacetate. This catalytic system can perform under mild conditions, and the desired cyclopropane products are obtained in high yields with excellent diastereoselectivity and enantioselectivity. 相似文献
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Thivisha Rajagopal 《Tetrahedron》2010,66(45):8739-8744
E-β-Chloro-α-iodo-α,β-unsaturated esters were converted to single isomer trisubstituted olefins bearing alkyl substituents by using and alkyl-Suzuki cross coupling. The process was highly selective, and the products in all cases were isolated as single isomers. Mechanistic investigations indicated that this process transfers a hydrogen from water to the α-position of the substrate, and then an alkyl group is introduced to the β-position of the intermediate template while replacing a chloride. 相似文献
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Olefins are cyclopropanated with dimethyl malonate (1a) iodosylbenzene (PhI=O) and a Rh(II) carboxylate catalyst via an in situ generated phenyliodonium ylide (1c). Enantioselectivities of up to 90% for 4-bromostyrene and 98% for pent-1-ene have been observed with (S)-N-4-bromo-1,8-naphthanoyl-tert-leucine (4c) as the chiral ligand. The same catalyst was effective for olefin cyclopropanation with Meldrum's acid, giving cyclopropanes with 96% (with styrene) and 87% ee (with pent-1-ene), respectively. 相似文献
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Shufeng Chen 《Tetrahedron letters》2008,49(48):6781-6783
A concise and efficient protocol for the preparation of cyclopropanes from various aryldiazocarbonyl compounds and electron-deficient olefins catalyzed by Pd(OAc)2 is reported. 相似文献
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[reaction: see text] Trisubstituted alkenes have been prepared via intermolecular olefin cross-metathesis (CM) between alpha-olefins and symmetrically 1,1-disubstituted olefins using an imidazolylidene ruthenium benzylidene complex. Of particular interest is the synthesis of isoprenoid/prenyl groups by a simple solvent-free CM reaction with isobutylene. In addition, prenyl groups can also be installed by a cross-metathesis of 2-methyl-2-butene with a variety of alpha-olefins at room temperature with low catalyst loadings. 相似文献
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V. A. D’yakonov R. A. Zinnurova A. G. Ibragimov U. M. Dzhemilev 《Russian Journal of Organic Chemistry》2007,43(7):956-960
An efficient one-pot procedure for the synthesis of trisubstituted olefins with Z-configured double bonds has been developed on the basis of cross coupling of 2,5-dialkylidenemagnesacyclopentanes (generated in situ) with alkyl, allyl, and aryl halides in the presence of transition metal (Cu, Zr, Fe, Co, Ni, Pd) salts and complexes. 相似文献
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《Tetrahedron: Asymmetry》2000,11(5):1157-1163
A new copper-(Schiff-base) complex, derived from (S)-2-amino-1,1-di(3,5-di-t-butylphenyl)propanol, 2-hydroxy-5-nitrobenzaldehyde and copper acetate monohydrate, was used as an efficient catalyst for the cyclopropanation of styrene with diazoacetates, affording ees of up to 98%. 相似文献
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《Tetrahedron: Asymmetry》2007,18(12):1403-1409
Three novel aryl sulfonamides derived from (2S)-indoline-2-carboxylic acid have been obtained and used as organocatalysts. The catalysts incorporate diverse functionality on the phenyl ring, enabling steric, and electronic fine tuning of the catalysts. The catalysts facilitate the reaction between a range of α,β-unsaturated aldehydes and sulfur ylides, thus providing cyclopropane products in enantiomeric excesses of up to 99%. 相似文献
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A. M. Moiseenkov V. A. Dragan A. V. Lozanova V. V. Veselovskii 《Russian Chemical Bulletin》1988,37(8):1603-1609
1. | Dimethyl, diphenyl, and tetramethylene sulfoxide hydrochlorides react with methylheptenyl, citronellyl, and geranyl acetates to give predominantly the allylic chlorination products. |
2. | These findings are preferably to be regarded as involving AdE reactions between the weakly electrophlic hydroxy and (or) chlorosulfonium cation and the trisubstituted C=C bond in these olefins at the key stage. |
3. | The addition of lithium perchlorate has been found to accelerate this reaction. |
4. | Sulfoxide hydrobromides are highly selective brominating agents for the terminal grouping in isopropenoid oligoolefins. |
20.
Phenylaziridine hydrazones react at 140°–160°C to provide sterically congested trisubstituted olefins in good yield. 相似文献