共查询到20条相似文献,搜索用时 15 毫秒
1.
Enantioselective N-heterocyclic carbene-catalyzed Michael addition reactions to α,β-unsaturated aldehydes by redox oxidation were realized. With 10 mol % of camphor-derived triazolium salt D, 15 mol % of DBU, 5 mol % of NaBF(4), and 100 mol % of quinone oxidant, the reactions of various dicarbonyl compounds with α,β-unsaturated aldehydes led to 3,4-dihydro-α-pyrones in good yields and excellent ee's. 相似文献
2.
A manganese-catalyzed bicyclic annulation of imines with α,β-unsaturated esters via C–H activation is described, which provides an expedient access to fused β-lactams in one-step operation with high efficiency and good functional group tolerance. Of note, both ketimines and aldimines are amenable to this transformation. Mechanistic studies have identified a five-membered azamanganacycle as the key reaction intermediate. 相似文献
3.
Zhang B Feng P Sun LH Cui Y Ye S Jiao N 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(30):9198-9203
In pole position: A simple and efficient approach to spirocyclic γ-lactam oxindoles by the N-heterocyclic carbene catalyzed addition of homoenloate equivalents to N-aryl isatinimines has been developed (see scheme). The use of N-aryl isatinimines as electrophiles in the NHC-catalyzed umpolung reaction of α,β-unsaturated aldehydes is demonstrated for the first time. 相似文献
4.
A nucleophilic carbene catalyzed redox esterification between α-halo-α,β-unsaturated aldehydes and various alcohols has been developed. Interestingly, the reaction provided α,β-unsaturated esters instead of the saturated α-halo substituted esters as the only product in good to high yield with excellent trans-selectivity, presumably via the umpolung-halo-elimination pathway. 相似文献
5.
A visible light-mediated approach for the preparation of α-bromo-α,β-unsaturated ketones and aldehydes was developed. In comparison to traditional methods that generally take two steps to afford the above compounds, this protocol was highlighted by its operational simplicity, avoiding using hazardous bromine and mild reaction conditions. 相似文献
6.
Tandem reactions of 1,2-allenic ketones leading to substituted benzenes and α,β-unsaturated nitriles
One-pot double Michael addition/intramolecular aldol reaction/decarboxylation of 1,2-allenic ketones with cyanoacetate offers an efficient and convenient approach to highly functionalized benzenes. With 2-substituted cyanoacetates, the reaction proceeds via a different tandem process to afford α,β-unsaturated nitriles effectively. 相似文献
7.
A practical synthetic procedure to hydrolytically cleave the C,C-double bond of α,β-unsaturated aldehydes and ketones has been developed. Secondary amines are employed as organocatalysts for the retro-aldol process under simple and mild reaction conditions. Beside the generation of the parent aromatic aldehydes, the synthetic procedure has been successfully used in a one-pot reaction sequence to convert simple cinnamaldehydes into their α-aryl/alkyl substituted derivatives. 相似文献
8.
A reaction between 3-isothiocyanato oxindoles and β,γ-unsaturated α-keto esters catalyzed by a chiral thiourea organocatalyst via a domino Michael-cyclization process is described, which delivers a range of biologically important 2′-thioxospiro[indoline-3,4′-oxazolidin]-2-one compounds in high yields with good diastereo- and enantioselectivities (up to 99% yield, >99:1 dr, >99% ee). Moreover, two of 2′-thioxospiro[indoline-3,4′-oxazolidin]-2-one compounds were found to significantly behave in anti-inflammatory activities in a preliminary biological evaluation. 相似文献
9.
《中国化学快报》2023,34(1):107487
Reversal of regioselectivity in the catalytic asymmetric conjugate additions of 3-substituted oxindoles to β-nitroenones or β-nitroacrylates was established with chiral scandium catalysts. It enabled the construction of functionalized 3,3-disubstituted oxindoles, including terminal and internal vinyl groups in excellent yields and ee values. 相似文献
10.
Francisco Palacios Ana M. Ochoa de RetanaSergio Pascual Guillermo Fernández de Trocóniz 《Tetrahedron》2011,67(8):1575-1579
A simple and efficient synthesis of fluoroalkylated α-amino nitrile (4) derivatives by regioselective 1,2-addition of trimethylsilyl cyanide to fluoroalkylated α,β-unsaturated imines (1) is described. Fluoroalkylated β-amino nitriles (7) are also prepared by regioselective 1,2-addition of α-carbanions derived from acetonitrile to fluoroalkylated α,β-unsaturated imines (1). Fluoroalkylated α-(4) and β-amino nitriles (7) are also prepared through an ‘one pot’ procedure by reaction of enaminophosphonate 2 with BuLi, addition of aldehydes and subsequent addition of either trimethylsilyl cyanide or α-carbanion derived from acetonitrile. Basic hydrolysis of α-(4) and β-amino nitriles (7) gives fluoroalkylated α-(5) and β-amino acids (8). 相似文献
11.
Yao C Wang D Lu J Li T Jiao W Yu C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(7):1914-1917
Carbenes ring true: N-Heterocyclic carbene (NHC) catalyzed reactions of α-bromo-α,β-unsaturated aldehydes/α,β-dibromoaldehydes with 1,3-dinucleophilic reagents, such as 1,3-dicarbonyl compounds, β-enamino ketones, and β-enamino esters through umpolung processes gave functionalized 3,4-dihydropyranones and 3,4-dihydropyridinones. The availability of the starting materials, lack of external oxidant, and usefulness of the products make this strategy attractive. 相似文献
12.
Efficient asymmetric Mannich addition reactions between α,β-unsaturated ketone derived enolates and N-phosphonyl imines were reported. These reactions could proceed smoothly for a variety of imine substrates with good (up to 96%) chemical yields and excellent diastereoselectivities (up to 98:2 dr). The method reported in this work provides an easy access to chiral β′-amino-α,β-enones. 相似文献
13.
Phosphonate reagents were developed for the two-carbon homologation of aldehydes or ketones to unbranched- or methyl-branched α,β-unsaturated aldehydes. The phosphonate reagents, diethyl methylformyl-2-phosphonate dimethylhydrazone and diethyl ethylformyl-2-phosphonate dimethylhydrazone, contained a protected aldehyde group instead of the usual ester group. A homologation cycle entailed condensation of the reagent with the starting aldehyde, followed by removal of the dimethylhydrazone protective group with a biphasic mixture of 1 M HCl and petroleum ether. This robust two-step process worked with a variety of aldehydes and ketones. Overall isolated yields of unsaturated aldehyde products ranged from 71% to 86% after the condensation and deprotection steps. 相似文献
14.
A [4+2] cycloaddition of α,β-unsaturated imines and isocyanates catalyzed by a phosphoramidite-rhodium complex provides pyrimidinones in good yields and high enantioselectivities. 相似文献
15.
Promoted by triethylamine, α,β-unsaturated N-acylbenzotriazoles reacted with amino compounds in a variety of ways. Thus, N-cinnamoylbenzotriazoles reacting with aromatic amines afforded novel addition products β-benzotriazolyl amides 3, which might be normally formed from the alternative but unknown 1,4-addition of benzotriazole to N-cinnamoylamides. The type 3 compounds could also result from the reaction between N-crotonoylbenzotriazole and aliphatic amines. However, normal 1,4-addition could occur between α,β-unsaturated aliphatic N-acylbenzotriazoles and aromatic amines, leading to β-amino N-acylbenzotriazoles 4 in good yields. In addition, exclusive 1,2-addition of aliphatic amines to N-cinnamoylbenzotriazoles gave excellent yields of cinnamides 5. Accordingly, three possible routes were proposed to rationalize the formation of compounds 3-5. Finally, with o-phenylenediamine and o-aminothiophenol as the substrates, the 1,4- and 1,2-addition to α,β-unsaturated N-acylbenzotriazoles could take place concurrently and the corresponding heterocycles 1,5-benzodiazepine-2-one and 1,5-benzothiazepine-4-one were constructed, respectively. 相似文献
16.
Chiral N-heterocyclic carbene catalyzed annulation of α,β-unsaturated aldehydes with 1,3-dicarbonyls
Zhu ZQ Zheng XL Jiang NF Wan X Xiao JC 《Chemical communications (Cambridge, England)》2011,47(30):8670-8672
Chiral N-heterocyclic carbene catalyzed annulations of ynals and enals with 1,3-dicarbonyls have been described. The two reactions provided direct and efficient methods for enantioselective synthesis of functionalized dihydropyranones. Comparatively, the reactions starting from ynals were atom-economical; furthermore the reactions of enals demonstrated broader substrate compatibility. 相似文献
17.
Catherine L. Moody Vilius Franckevičius Pauline Drouhin Johannes E.M.N. Klein Richard J.K. Taylor 《Tetrahedron letters》2012,53(15):1897-1899
A practical and efficient entry to spirocyclic oxindoles from readily accessible anilide precursors, using only catalytic amounts of an inexpensive copper salt together with air as the sole re-oxidant, is described. In addition to providing access to a broad range of spiro-oxindole products, the utility of this method is demonstrated in a formal synthesis of the natural product, horsfiline. 相似文献
18.
2-Fluoro-6-pyridinyloxy derivatives of 2-ethoxyvinyl carbinols react with radicals derived from xanthates by an addition-fragmentation pathway to give highly functionalized ketones after acid hydrolysis. 1,4-Diketones are readily accessible by this approach. α,β-Unsaturated ketones can be obtained by starting with geminal acetoxy xanthates prepared by addition of a simpler xanthate to vinyl acetate. 相似文献
19.
Lewis base-catalyzed cyclization reactions of allenoates with electron-deficient olefins and imines have been demonstrated by the preparation of biologically active natural products and pharmaceutically interesting substances and have emerged as powerful synthetic tools in the rapid construction of cyclic molecular complexity. In contrast to phosphine-containing Lewis bases, nitrogen-containing Lewis base amines display markedly different reaction profiles; however, this area is not well-developed. Herein we summarize the recent progress in this emerging field and outline the challenges ahead. 相似文献
20.
Shuwen He Zhong Lai David X. Yang Qingmei Hong Mikhail Reibarkh Ravi P. Nargund William K. Hagmann 《Tetrahedron letters》2010,51(33):4361-4364
We report an efficient method for the synthesis of β-carbolines from α-siloxy α,β-unsaturated esters, which are accessible from a variety of aldehydes and ketones. 相似文献