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1.
A series of chiral phosphine PFAM and phosphine oxide POFAM ligands were studied for the copper-catalyzed asymmetric diethylzinc addition to enones. One of these ligands, PFAM2, was an efficient catalyst with a variety of enones to give conjugate addition products in up to 96% yield and 92% ee.  相似文献   

2.
3.
Ace of base: A catalytic system is presented that, solely by choice of the base, selectively switches between conjugate addition and the Mizoroki-Heck reaction of aryl halides with Michael acceptors (see scheme; R, R' = alkyl, aryl). For conjugate addition reactions, this avoids the preparation and use of organometallics.  相似文献   

4.
Organometallics readily add to the double bond of 1-(functionally substituted alkene phosphonates to give highly substituted phosphonates.  相似文献   

5.
A tandem conjugate addition/cyclisation approach, that allows the synthesis of chiral highly substituted cyclohexanones and cyclohexenones, which is applicable to natural product syntheses has been developed.  相似文献   

6.
In the formation of new bonds through the Michel‐type addition of thiolates to a α,β‐conjugate system, it is observed that the reaction takes place faster if the thio donor compound contains an electron‐rich group or the enone acceptor is highly electron deficient. In contrast, the hard–soft acid–base (HSAB) principle predicts that this reaction is favored when a soft–soft interaction between the reactants takes place. Taking into account that softness is related to a barely electronegative atom of high polarizability, we consider it of interest to analyze the effect of charge transfer of a p‐substituent on the softness of sulfur in thiophenols, as well as its impact in the conjugate addition to 2‐cyclohexen‐1‐one. Experiments‐in‐competition, net charge of X‐groups at the p‐position of the aromatic ring, the global and local softness at sulfur, and the electrophilicity, obtained by density functional theory (DFT), led to the observation that the reaction is faster for electron attractor thiophenols. The softness at sulfur increases by delocalization of charge through the aromatic ring. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005  相似文献   

7.

Abstract  

Water-promoted hydrothiolation and hydroamination of ethyl propiolate leading to highly regioselective and stereoselective formation of thioacrylates and β-enamino esters in excellent yields, by a simple, efficient, and environmentally friendly reaction procedure without employing any hazardous reagent or solvent is reported.  相似文献   

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9.
The first catalytic enantioselective addition of beta-dicarbonyl compounds to alkynones is presented. The conjugate addition proceeds in very high yields, giving a mixture of (Z)- and (E)-enones with up to 95% ee using the cinchona alkaloid [DHQ]2PHAL (5 mol %) as the catalyst. This organocatalytic enantioselective reaction has been further developed to a one-pot procedure to give the optically active (E)-enone adduct using first [DHQ]2PHAL (5 mol %), followed by Bu3P (10 mol %), as the catalysts.  相似文献   

10.
Tong BM  Chiba S 《Organic letters》2011,13(11):2948-2951
Diamines were found to promote catalytic conjugate addition of α-cyano active methine nucleophiles to various acrylate derivatives.  相似文献   

11.
《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   

12.
The reaction of tributyltin lithium with Fischer type alkynyl carbene complexes has been studied. The reaction proceeds via a nucleophilic pathway to produce the conjugate addition product, and a single electron transfer pathway to afford cyclopentannulated derivatives derived from two units of the alkyne complex. Structure of the latter was confirmed by crystal structure determination of a representative complex.  相似文献   

13.
《Tetrahedron: Asymmetry》2000,11(19):3849-3853
The conjugate addition of methylcuprates and methyllithium to ethyl 5-phenyl-1,3-dioxolan-4-yl-2-propenoate was investigated. It was found that the stereoselectivity is highly dependent on the reagent used. In reactions with stabilized methylcuprates, the anti-1,4-addition product is mainly formed, whereas syn-diastereoselectivity is observed in the reaction with methyllithium. Additions of methyllithium were optimized with respect to solvent and additives.  相似文献   

14.
The introduction of alkyl substituents at C-2 of chromanones via conjugate addition of silyl enol ethers to a variety of chromenones is reported. In most cases racemic 2-alkyl chromanones were obtained in good yield in the presence of TMSOTf. The copper(II)-promoted conjugate addition of silyl enol ethers to chromenones was also carried out, albeit in low yields and no selectivity. Reliable syntheses of the chromenones via acylation of the corresponding β-diketo-compounds are also described.  相似文献   

15.
Enantioselective conjugate radical addition to alpha'-hydroxy alpha,beta-unsaturated ketones, compounds containing bidentate donors, has been investigated. It has been found that radical additions to alpha'-hydroxy alpha,beta-unsaturated ketones in the presence of Mg(NTf2)2 and bisoxazoline ligand 5a proceeded cleanly, yielding the addition products in high chemical yields and good enantiomeric excesses.  相似文献   

16.
Lee S  Kim S 《Organic letters》2008,10(19):4255-4258
Catalytic enantioselective radical conjugate addition reactions using alpha'-phosphoric enone templates have been studied. The C 2-symmetric bisoxazoline-zinc(II) complex proves to be effective for high enantioselectivities and chemical yields. In addition, intermediate alpha-carbonyl alkyl radicals could be trapped with allyltributylstannane to afford anti-isomers as major products with high enantioselectivities.  相似文献   

17.
Alkynyl heteroaromatic compounds reacted with arylboronic acids to give addition products in the presence of a rhodium catalyst. The best results were obtained when a novel pyridine-substituted water-soluble phosphine ligand was used. The reactions proceed to give trisubstituted alkenes from various arylboronic acids and alkynyl heteroaromatic compounds with high regioselectivity. Only alkynes with a nitrogen atom in proximity to the triple bond were converted to the corresponding alkenes, as expected for a chelation-controlled addition.  相似文献   

18.
A facile introduction of alpha,beta- or alpha,beta,gamma,delta-unsaturated ester functions onto porphyrins was achieved through rhodium-catalyzed addition of beta-borylporphyrins to acrylate or 2,4-pentadienoate esters. The reaction of meso-borylporphyrins with acrylates exclusively afforded saturated esters by 1,4-conjugate addition under the same reaction conditions. Thus, the reaction mode (Heck-type versus conjugate addition) is highly dependent on the reaction site (beta versus meso). This functionalization has a significant impact on the electronic properties of the pi system of porphyrins, which induces a substantial redshift and broadening in the absorption spectra by effective conjugation through the beta positions. The coplanar structure of the unsaturated ester moieties with respect to the porphyrin core has been unambiguously elucidated by X-ray crystallographic analysis.  相似文献   

19.
Jin T  Yamamoto Y 《Organic letters》2007,9(25):5259-5262
The reaction of the internal alkynyl ketones 1 (n=1) under the combined catalyst, AuCl3 and AgSbF6, gave the enones 2 in good to high yields, whereas that of the terminal alkynyl ketones 1 (n=0) under the combined catalyst, AuCl3 and AgOTf, afforded the cyclic enones 3.  相似文献   

20.
The dibromocarbene or bromofluorocarbene addition to substituted allyldisilanes afforded instable gem-dibromocyclopropanes or a gem-bromofluorocyclopropane, respectively. These gem-bromohalogenocyclopropanes undergo a spontaneous ring opening at room temperature to give halogenated dienylsilanes or bromo dienes or dibromotetraenes.  相似文献   

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