共查询到20条相似文献,搜索用时 15 毫秒
1.
Nishimura T Sawano T Ou K Hayashi T 《Chemical communications (Cambridge, England)》2011,47(36):10142-10144
Catalytic addition of silylacetylenes to α,β-unsaturated ketones proceeded in the presence of a cobalt complex coordinated with a bisphosphine ligand to give high yields of β-alkynylketones. 相似文献
2.
Marco Bandini 《Tetrahedron letters》2003,44(31):5843-5846
Chiral [Al(salen)Cl] complex (10 mol%) in the presence of 2,6-lutidine (10 mol%) was found to be effective in catalysing the enantioselective Friedel-Crafts-type conjugate addition of indoles (3) to (E)-arylcrotyl ketones (2), furnishing the corresponding β-indolyl ketones in excellent yield and high enantioselectivity (ee up to 89%). 相似文献
3.
《Tetrahedron: Asymmetry》2014,25(13-14):974-979
Perfluoroalkanesulfonamide organocatalyst 7 efficiently promotes asymmetric Michael additions of malonates to enones in cyclohexane or water to produce the corresponding addition products with excellent yields and with up to 99% ee. 相似文献
4.
Hyoung Wook Moon 《Tetrahedron letters》2010,51(21):2906-380
The catalytic enantioselective conjugate addition reaction of α-nitroacetate to α,β-unsaturated ketones promoted by chiral bifunctional organocatalysts is described. The treatment of α-nitroacetate to α,β-unsaturated ketones under aqueous-phase reaction conditions afforded the corresponding Michael adducts with high enantioselectivity. The conjugate addition adducts are easily converted to chiral δ-keto nitroalkanes and δ-keto esters. 相似文献
5.
Silvia RoscalesÁngela Rincón Eduardo BuxaderasAurelio G. Csákÿ 《Tetrahedron letters》2012,53(35):4721-4724
The conjugate addition of boronic acids to α,β-unsaturated ketones catalyzed by acylating reagents has been explored. The results show that trifluoroacetic anhydride catalyzes the addition of vinylboronic acids under experimentally simple and metal-free conditions for a variety of substrates with good yields. 相似文献
6.
Conjugate addition of alkylboron compounds (alkyl-9-BBN) to imidazol-2-yl α,β-unsaturated ketones proceeded in the presence of a catalytic amount (10 mol %) of CuCl, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), and t-BuOK. The alkylboranes are available through alkene hydroboration, and thus the overall process represents a reductive conjugate addition of alkenes to enone derivatives. A variety of functional groups are tolerated in both the alkenes and the α,β-unsaturated ketones. The 2-acylimidazole moiety can easily be converted into the corresponding carboxylic acid, ester, and amide derivatives. 相似文献
7.
The catalytic asymmetric phospha-Michael reaction of dialkyl phosphine oxides with β,β-disubstituted α,β-unsaturated carbonyl compounds was achieved. The products bearing tetrasubstituted carbon stereocenters were obtained in high yields with excellent enantioselectivities (up to >99% ee). 相似文献
8.
Haohua Chen Lei Zhu Kangbao Zhong Xiaoyu Yue Ling-Bo Qu Ruopeng Bai Yu Lan 《中国化学快报》2018,29(8):1237-1241
A theoretical investigation of the mechanism and origin of enantioselectivity for phosphoric acid-catalyzed asymmetric conjugate addition of indolizines to α,β-unsaturated ketones. 相似文献
9.
Manzano R Andrés JM Álvarez R Muruzábal MD de Lera ÁR Pedrosa R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(21):5931-5938
A series of chiral thioureas derived from easily available diamines, prepared from α-amino acids, have been tested as catalysts in the enantioselective Michael additions of nitroalkanes to α,β-unsaturated ketones. The best results are obtained with the bifunctional catalyst prepared from L-valine. This thiourea promotes the reaction with high enantioselectivities and chemical yields for aryl/vinyl ketones, but the enantiomeric ratio for alkyl/vinyl derivatives is very modest. The addition of substituted nitromethanes led to the corresponding adducts with excellent enantioselectivity but very poor diastereoselectivity. Evidence for the isomerization of the addition products has been obtained from the reaction of chalcone with [D(3)]nitromethane, which shows that the final addition products epimerize under the reaction conditions. The epimerization explains the low diastereoselectivity observed in the formation of adducts with two adjacent tertiary stereocenters. Density functional studies of the transition structures corresponding to two alternative activation modes of the nitroalkanes and α,β-unsaturated ketones by the bifunctional organocatalyst have been carried out at the B3LYP/3-21G* level. The computations are consistent with a reaction model involving the Michael addition of the thiourea-activated nitronate to the ketone activated by the protonated amine of the organocatalyst. The enantioselectivities predicted by the computations are consistent with the experimental values obtained for aryl- and alkyl-substituted α,β-unsaturated ketones. 相似文献
10.
Taichi Kano 《Tetrahedron》2007,63(35):8658-8664
A 1,4-addition of alcohols to α,β-unsaturated aldehydes was found to be efficiently promoted by biphenyldiamine-based catalyst 3 without formation of the acetals. An asymmetric variant of this reaction has also been performed by designing a novel axially chiral organocatalyst (R)-10c. 相似文献
11.
Michael addition of indole and pyrrole to a variety ofα,β-unsaturated ketones was efficiently promoted by a catalytic amount of GaCl_3 in aqueous media to afford the corresponding products in good to excellent yields. 相似文献
12.
A bulky group was introduced by design into a diamine catalyst, and a series of robust and tunable bulky chiral primary amine catalysts were developed and successfully applied in the direct conjugate addition of substituted rhodanines to α,β-unsaturated ketones. High yields (up to 99%) and excellent diastereoselectivities (up to 99:1 dr) and enantioselectivities (up to 98% ee) were observed. 相似文献
13.
A novel rhodium-catalyzed conjugate addition of indium reagents to electron deficient olefins is reported. The reaction takes place in THF/MeOH at 110 °C using arylindium dichlorides, a rhodium(I)-binap complex as catalyst, and α,β-unsaturated ketones and lactones in good yields (45–94%). The addition of MeOH is crucial for an efficient transformation and NMR studies seem to indicate that promotes the catalytic cycle leaving the indium organometallic unaltered. The use of chiral non-racemic ligands allows performing the reaction with moderate enantioselectivities. 相似文献
14.
Jun-min Zhang 《Tetrahedron》2009,65(4):802-1509
A variety of secondary amines were studied as the catalyst in the conjugate addition of 1-bromonitromethane to α,β-unsaturated aldehydes. Proline was identified as the best catalyst for this reaction. MeOH/AcONa system was found to provide much better yields than CHCl3/Et3N system reported before. Good yields of nitrocyclopropane products were obtained with a variety of β-aryl acroleins. Several substituted 1-bromonitromethanes were also examined in the reaction. Both 1-bromonitroethane and 1-phenyl-1-bromonitromethane gave the corresponding nitrocyclopropanes in good yields. The diastereoselectivity of the reaction was strongly affected by the steric hindrance of 1-bromonitroalkanes. 相似文献
15.
《Tetrahedron letters》1986,27(13):1437-1440
Lithium Triorganozincates of the type RR′2ZnLi, where R′ = Me and R = n-Bu or sec-Bu, efficiently transfer the R group in a 1,4 fashion to α,β-unsaturated ketones. 相似文献
16.
17.
Organocatalytic conjugate addition of thioacids to α,β-unsaturated ketones has been studied in the presence of cinchona alkaloid derived urea catalyst. Both the enantiomers of products are accessible with the same level of enantioselectivity using pseudoenantiomeric quinine/quinidine derived catalysts. The catalytic process provides optically active thioesters with high chemical yields (up to 99%) and useful enantioselectivity (up to 83% ee). The reaction was performed with 1 mol % of catalyst in toluene at room temperature. A transition state model has been proposed to explain the stereochemical outcome of the reaction. 相似文献
18.
Catalytic asymmetric conjugate addition of nitroalkanes to α,β-unsaturated thioamides is promoted by a mesitylcopper/(R)-DTBM-Segphos precatalyst, affording γ-nitrothioamides in moderate to high syn-selectivity and excellent enantioselectivity. The intermediate Cu-thioamide enolate functions as a soft Lewis acid/hard Br?nsted base cooperative catalyst to drive the catalytic cycle efficiently under proton transfer conditions. 相似文献
19.
Li-ting Dong 《Tetrahedron》2009,65(21):4124-1541
Asymmetric conjugate addition of 1-bromonitroalkanes to α,β-unsaturated ketones was studied using chiral primary amines as the catalysts. 9-Amino-9-deoxyepiquinine was found to be highly efficient catalyst for the transformation. 4-Bromo-4-nitroketones were obtained with excellent enantioselectivities (97-99% ee) and good yields (61-99%) for a variety of alkyl vinyl ketones. The product could be further debrominated with Bu3SnH/AIBN to provide chiral 4-nitroketones in good yield and without loss of the optical purity. 相似文献