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1.
Vázquez J Prieto A Fernández R Enders D Lassaletta JM 《Chemical communications (Cambridge, England)》2002,(5):498-499
Enantiopure formaldehyde N,N-dialkylhydrazones 1 smoothly react with prochiral alkylidene malonates 2 in the presence of MgI2 to afford the corresponding Michael adducts 3 in excellent yields and good diastereoselectivities; direct racemization-free BF3.OEt2-catalyzed thiolysis of the hydrazone C=N bond affords the corresponding dithioketals 7 in optically pure or enantiomerically enriched form. 相似文献
2.
《Tetrahedron: Asymmetry》2001,12(8):1151-1157
Dialkylzinc and trialkylaluminium reagents undergo conjugate addition to alkylidene malonates with 0.5% copper triflate as catalyst. The reaction could be made enantioselective by completing the reaction in the presence of 0.5–1.0 mol% of chiral phosphorus ligand. Enantiomeric excesses (e.e.s) of up to 73% could be attained with a ligand prepared from TADDOL and 2-naphthylcyclohexanol. 相似文献
3.
The conjugate spontaneous addition of chiral N,N-dialkylhydrazines 1 to dimethyl alkylidene/arylidene malonates 2, 5-10 affords the corresponding β-hydrazino esters in moderate-to-good yields and selectivities. d-Mannitol-derived hydrazine 1a afforded best results, mainly due to the higher stability of the products 3, 11-16. 相似文献
4.
Enantioselective organocatalytic Michael addition of malonates to α,β-unsaturated aldehydes in water
Anqi Ma 《Tetrahedron letters》2008,49(19):3075-3077
The Michael addition of malonates to α,β-unsaturated aldehydes catalyzed by O-TMS protected diphenylprolinols and acetic acid in water occurs at 0 °C to rt. In most cases, the reaction runs to completion in less than 24 h. A wide range of aldehydes including β-aryl, β-alkyl and β-alkenyl acroleins are found to be compatible with these conditions, providing the corresponding adducts in good yields and with good to excellent enantioselectivities. 相似文献
5.
Cinchona alkaloid derived primary amine thioureas organocatalyzed Michael addition of nitroalkanes to enones in good yield and up to 98% ee and offered a new way to construct quaternary stereocenters from enones and nitroalkanes. 相似文献
6.
A pseudo-C3-trisoxazoline was designed and synthesized. The improvement of the traditional bisoxazoline into a novel trisoxazoline by a sidearm approach resulted in highly catalytic enantioselective Michael addition of indoles to alkylidene malonates. Excellent catalytic reactivity and enantioselectivity (up to 99% yield and 93% ee) were achieved. 相似文献
7.
A practical and highly enantioselective Michael addition of malonates to enones catalyzed by simple and readily available bifunctional primary amine-thiourea derived from 1,2-diaminocyclohexane is reported. The addition of weak acids and elevated temperature (ca. 50 °C) improved the efficiency of the Michael reaction. This approach enables the efficient synthesis of 1,5-ketoesters with good yields, excellent enantioselectivities (up to 99% ee), and low loading (0.5-5 mol %) of simple chiral primary amine-thiourea catalysts, and is applicable in multigram scale synthesis. 相似文献
8.
[reaction: see text] A novel organocatalytic, enantioselective domino double Michael addition reaction of alpha,beta-unsaturated aldehydes with ethyl 4-mercapto-2-butenoate has been developed. The process is promoted by chiral diphenylprolinol TMS ether to give chiral tetrahydrothiophenes in high to excellent levels of enantioselectivities. 相似文献
9.
5-Pyrrolidin-2-yltetrazole performs as a useful organocatalyst for the asymmetric addition of malonates to a range of enones, with good to excellent enantioselectivities. 相似文献
10.
11.
M. Lakshmi Kantam Kalluri V.S. Ranganath Lakkoju Chakrapani 《Tetrahedron letters》2007,48(43):7646-7649
Highly enantioselective Michael addition of malonates to cyclic and acyclic enones has been achieved by using nanocrystalline magnesium oxide at −20 °C. 相似文献
12.
《Tetrahedron: Asymmetry》2001,12(17):2395-2398
The conjugate addition of O-benzylhydroxylamine and N,O-bis(trimethylsilyl)hydroxylamine to alkylidene and arylidene malonates in the presence of Lewis acids affords the corresponding β-hydroxylamino derivatives in good yields. The use of Cu(OTf)2 in the presence of chiral bisoxazoline ligands opens the possibility of performing this reaction in a catalytic and enantioselective way. 相似文献
13.
A carbon-carbon bond was formed at the β-position of cyclic ketones in a one-pot manner by oxidation with N-tert-butylbenzenesulfinimidoyl chloride, followed by the reaction of malonic acid esters or potassium cyanide. 相似文献
14.
《Tetrahedron: Asymmetry》2014,25(6-7):516-522
An organocatalyzed direct Michael addition of unsubstituted/substituted malonates, acetoacetate, or acetylacetones to conjugated nitrodienes using a cinchona alkaloid-based thiourea catalyst is disclosed. The addition products were formed in high yields and regioselectivity. The enantioselectivities of the addition products were high in most cases and could significantly be improved upon by a single recrystallization. The addition products easily undergo chemoselective nitro group reduction and subsequent lactamization with a high synthetic potential. 相似文献
15.
Alcaine A Marqués-López E Merino P Tejero T Herrera RP 《Organic & biomolecular chemistry》2011,9(8):2777-2783
Bifunctional thiourea catalyzes the enantioselective Michael addition reaction of diphenyl phosphite to nitroalkenes. This methodology provides a facile access to enantiomerically enriched β-nitrophosphonates, precursors for the preparation of synthetically and biologically useful β-aminophosphonic acids. DFT level of computational calculations invoke the attack of the diphenyl phosphite to the nitroolefin by the Re face, this give light to this scarcely explored process update in the literature. The computational calculations support the absolute configuration obtained in the final adducts. 相似文献
16.
Alkylidene malonates undergo efficient conjugate allylation upon treatment with allylstannanes or allylsilanes under the action of ytterbium catalysis. 相似文献
17.
[reaction: see text] A method for Michael addition of N-heterocycles to nitroolefins has been developed. The process is promoted by a cinchona alkaloid derivative to give Michael adducts in moderate to high enantioselectivities. 相似文献
18.
The asymmetric direct Michael addition of aromatic ketones to highly active alkylidenemalononitriles was investigated by employing a chiral primary amine 9-amino-9-deoxyepicinchonine. In general modest to good enantioselectivities (71–84% ee) could be obtained in acceptable isolated yields (48–85%) for an array of substrates. 相似文献
19.
A surfactant-type asymmetric organocatalyst (STAO) catalyzed highly efficient Michael addition to nitroalkenes with high stereoselectivities in water without using any organic solvents or additional additives. 相似文献
20.
A short and efficient synthesis of tetrahydroindenofuranones based on the Michael addition of ortho-lithiated aryloxiranes to alkylidene malonates followed by the nucleophilic oxirane ring-opening and subsequent lactonization is described. The methodology has been applied to the synthesis of a structural analogue of epipodophyllotoxins. 相似文献