The first example of a highly enantioselective organocatalytic aziridination of α‐substituted α,β‐unsaturated aldehydes is presented. The reaction is catalyzed by simple chiral amines and gives access to highly functional terminal azirdines containing an α‐tertiary amine stereocenter in high yields and enantiomeric ratios (95.5:4.5–98:2). 相似文献
A highly chemo‐ and enantioselective organocatalytic cyclopropanation of α,β‐unsaturated aldehydes with bromomalonate and 2‐bromoacetoacetate esters is presented. The reaction is catalyzed by chiral amines and gives access to 2‐formylcyclopropanes in high yields and up to 99 % ee. 相似文献
An efficient and generally applicable protocol for decarboxylative coupling of α,α‐difluoroarylacetic acids with ethynylbenziodoxolone (EBX) reagents has been developed, affording α,α‐difluoromethylated alkynes bearing various functional groups in moderate to excellent yields. Remarkably, this potassium persulfate (K2S2O8)‐promoted reaction employs water as solvent under transition metal‐free conditions, thus providing a green synthetic approach to α,α‐difluoromethylated alkynes.
An organocatalytic approach for the stereoselective synthesis of 3,4‐dihydrocoumarins with an α,α‐disubstituted amino acid moiety incorporated is presented. The developed methodology is based on the cascade reaction between α‐substituted azlactones and 2‐hydroxychalcones. It is initiated by a chiral Brønsted base‐catalyzed enantio‐ and diastereoselective Michael reaction followed by the azlactone ring opening to construct a 3,4‐dihydrocoumarin framework. Products bearing two adjacent stereogenic centers, one being quaternary, were formed with high enantioselectivities and excellent diastereoselectivities. Furthermore, the complete regioselectivity of the new cascade reactivity is worthy of notice.
Efficient one‐step syntheses of α,β‐ and β,β‐dihaloenones were achieved by ruthenium(II)‐catalyzed reactions between cyclic or acyclic diazodicarbonyl compounds and oxalyl chloride or oxalyl bromide in moderate to good yields. This methodology offers several significant advantages, which include ease of handling, mild reaction conditions, one‐step reaction, and the use of an effective and non‐toxic catalyst. The synthesized compounds were further transformed into highly functionalized novel molecules bearing aromatic rings on the enone moiety using the Suzuki reaction.
Herein, we disclose the N‐heterocyclic carbene (NHC)‐catalyzed [3+3] annulation of challenging esters with methyl ketoimines for the highly enantioselective synthesis of intriguing δ‐lactams featuring various substituent patterns. The annulation occurs under mild conditions and offers good tolerance, good yields and excellent enantioselectivities. The six‐membered heterocyclic products are valuable for the synthesis of bioactive molecules.
A regio‐ and enantioselective copper‐catalyzed 1,4‐conjugate addition of trimethylaluminium to linear δ‐aryl‐substituted α,β,γ,δ‐unsaturated alkyl ketones was developed. A series of γ,δ‐unsaturated alkyl ketones were obtained in good yields with high regio‐ and enantioselectivity (up to 88% ee and 96:4 dr). Expansion of the reaction scope to substrates containing aromatic heterocycles also afforded good yields and enantioselectivities (up to 91% ee) with very high regioselectivities, exclusively providing the single 1,4‐products.
(2S,3aR,7aS)‐Perhydroindolic acid, the key intermediate in the synthesis of trandolapril, and its trans‐isomers, were readily prepared. These proline‐like molecules are unique in that they contain a rigid bicyclic structure, with two hydrogen atoms trans to each other at the bridgehead carbon atoms. These molecules were used successfully as chiral organocatalysts in asymmetric domino Michael addition/cyclization reactions of aldehyde esters with β,γ‐unsaturated α‐keto esters. They proved to have excellent catalytic behavior, allowing for the synthesis of multi‐substituted, enantiomerically enriched hemiacetal esters. Under optimal conditions (using 10 mol% catalyst loading), a series of β,γ‐unsaturated α‐keto esters was examined with up to 99% de, ee and yield, respectively. Additionally, the enantiomerically enriched hemiacetal esters could be readily transformed into their corresponding bioactive pyrano[2,3‐b]pyrans (possessing a multi‐substituted bicyclic backbone). 相似文献
A highly enantioselective Michael addition of cyclic 1,3‐dicarbonyl compounds to β,γ‐unsaturated α‐keto esters catalyzed by amino acid‐derived thiourea‐tertiary‐amine catalysts is presented. Using 5 mol% of a novel tyrosine‐derived thiourea catalyst, a series of chiral coumarin derivatives were obtained in excellent yields (up to 99%) and with up to 96% ee under very mild conditions within a short reaction time. 相似文献
The Heck arylation of α,β‐unsaturated aldehydes is strongly dependent on the catalyst, the solvent and the base. Optimized conditions yielded either selectively cinnamyl derivatives (83%) or double arylation products (88% based on aryl conversion). A new α‐arylation of β,β‐disubstituted acrolein is also realized. 相似文献
The highly enantioselective organocatalytic domino aza‐Michael/aldol reaction is presented. The unprecedented, chiral amine‐catalyzed asymmetric domino reactions between 2‐aminobenzaldehydes and α,β‐unsaturated aldehydes proceed with excellent chemo‐ and enantioselectivity to give the corresponding pharmaceutically valuable 1,2‐dihydroquinolines derivatives in high yields with 90 to >99 % ee. 相似文献
Nanocrystalline magnesium oxide was found to be an effective heterogeneous, solid base catalyst for the one‐pot Wittig reaction to afford α,β‐unsaturated esters and nitriles in excellent yields with high E‐stereoselectivity in the presence of triphenylphosphine under mild conditions. 相似文献
The first organocatalytic enantioselective aza‐Michael addition of purine bases to α,β‐unsaturated ketones has been developed, affording Michael adducts in moderate to high yields (up to 96% yield) and high to excellent enantioselectivities (up to >99% ee). A wide range of α,β‐unsaturated ketones including aliphatic and aromatic enones are tolerated in this process, generally demonstrating good reactivity, regioselectivity and enantioselectivity. The aromatic α,β‐unsaturated ketones showing quite low reactivity in the reported catalytic systems, were first successfully employed as Michael acceptors in this transformation, yielding high enantioselectivities (up to 94% ee). The utility of this method was also applied for the synthesis of enantioenriched non‐natural nucleoside analogues with potential biological activities. 相似文献
In the presence of the readily available quinine‐derived catalyst 4d , highly diastereo‐ and enantioselective Mannich reactions of tosyl‐protected imines and α‐isothiocyanato imides proceeded to afford the protected α,β‐diamino acids, useful building blocks for natural products and biologically active compounds, in good to excellent yields. 相似文献
The first catalytic synthesis of β,γ‐alkynyl α‐amino acid derivatives was achieved by direct addition of terminal alkynes to α‐imino esters in the presence of an Ag(I) salt under mild reaction conditions. 相似文献
We have developed and optimized an enantioselective Michael reaction of malononitrile with β,β‐disubstituted nitroalkenes. This reaction was catalyzed by a cinchona alkaloid derived thiourea catalyst, producing products of high yields (up to 98 %) and stereoselectivities (up to 93 % ee). One of the adducts was used as an intermediate for the synthesis of dihydropyrrole derivative bearing a synthetically valuable quaternary chiral center.
An efficient and convenient method was developed for the one‐pot construction of the complex polycyclic heterocycles pyrrolo[1,2‐a:2′,1′‐c]‐/pyrido[2,1‐c]pyrrolo[1,2‐a]quinoxalinones from two simple starting materials via a gold(I)‐catalyzed domino reaction. This strategy presents an atom economical and environmentally friendly transformation, in which two new C N bonds and one new C C bond are formed in a one‐pot reaction process. 相似文献
Chemoselective reduction of α,β‐unsaturated carbonyls to the corresponding alcohols was achieved by a catalytic transfer hydrogenation (CTH) method using cobalt(II)‐substituted hexagonal mesoporous aluminophosphate (CoHMA) molecular sieve catalyst. Further, the catalyst was found to be promising as a heterogeneous catalyst as the yield was practically unchanged after up to six cycles. 相似文献