The first organocatalytic Mannich reaction of 5H‐oxazol‐4‐ones with various readily prepared aryl‐ and alkylsulfonimides has been developed. Two commercially available pseudoenantiomeric Cinchona alkaloids‐derived tertiary amine/ureas have been demonstrated as the most efficient catalysts to access the opposite enantiomers of the Mannich products with equally excellent enantio‐ and diastereoselectivities. From the Mannich adducts, important α‐methyl‐α‐hydroxy‐β‐amino acid derivatives, such as the α‐methylated C‐13 side chain of taxol and taxotere, can be conveniently prepared. 相似文献
A highly enantioselective Michael addition of 3‐substituted benzofuran‐2(3H)‐ones to chalcones catalyzed by a chiral bifunctional thiourea was developed. Several chiral 3,3′‐substituted benzofuran‐2(3H)‐ones derivatives, bearing adjacent quaternary‐tertiary stereocenters, were efficiently synthesized with excellent enantioselectivities. 相似文献
An organocatalytic Michael addition of protected 2‐amino‐1‐nitroethanes to α,β‐unsaturated aldehydes followed by treatment with TFA afforded 4‐substituted 3‐nitro‐1,2,3,4‐tetrahydropyridines with good diastereoselectivity and excellent enantioselectivity. Good yields were observed in the case of β‐aryl‐substituted α,β‐unsaturated aldehydes as the substrates, while moderate yields were obtained when β‐alkyl‐substituted α,β‐unsaturated aldehydes were used. 相似文献
An efficient and divergent one‐pot synthesis of substituted 2H‐pyrans, 4H‐pyrans and pyridin‐2(1H)‐ones from β‐oxo amides based on the selection of the reaction conditions is reported. Mediated by N,N,N′,N′‐tetramethylchloroformamidinium chloride, β‐oxo amides underwent intermolecular cyclizations in the presence of triethylamine at room temperature to give substituted 2H‐pyrans in high yields, which could be converted into substituted 4H‐pyrans in the presence of sodium hydroxide in ethanol at room temperature, or into substituted pyridin‐2(1 H)‐ones under reflux. 相似文献
The first organocatalytic diastereo‐ and enantioselective Michael addition reaction of 4‐substituted‐pyrazolin‐5‐ones to nitroolefins has been developed with a chiral bifunctional thiourea as organocatalyst. A wide variety of desired multi‐substituted pyrazolin‐5‐one derivatives with contiguous quaternary and tertiary stereocenters are smoothly obtained in very good yields (up to 98%) with excellent enantioselectivities (up to>99% ee) and acceptable diastereoselectivities (up to 80:20). This experimentally simple process facilitates the access to various enantioenriched, multiply substituted pyrazolin‐5‐one derivatives, potential biologically active molecules, starting from readily available starting materials. 相似文献
A four‐electron electrocyclic ring‐opening/intermolecular [4+2] cycloaddition of α‐hydroxycyclobutenones is reported. The reaction represents the first example for the intermolecular cycloaddition of the extensively studied enol‐ketene intermediate, and provides a new synthetic route to multiply substituted δ‐lactams in high stereoselectivity.
Nanocrystalline ZnO is an effective heterogeneous catalyst for the [2+3]‐cycloaddition of sodium azide with nitriles to afford 5‐substituted 1H‐tetrazoles in good yields. 相似文献
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
The Pd‐catalyzed decarboxylative cross‐coupling reaction of 4‐substituted quinolin‐2(1H)‐one‐3‐carboxylic acids with (hetero)aryl halides is described. With palladium(II) bromide and triphenylarsine ligand as the catalyst system, a variety of 4‐substituted 3‐(hetero)aryl quinolin‐2(1 H)‐ones and related heterocycles, such as 4‐substituted 3‐arylcoumarins can be prepared in good to excellent yields. 相似文献
An efficient asymmetric synthesis of spirocyclohexenone β‐lactams bearing three contiguous stereocenters has been achieved in moderate to good yields and high stereoselectivities. The protocol involves the combination of a squaramide‐catalyzed sulfa‐Michael addition under desymmetrization via a dynamic kinetic resolution of racemic 2,5‐cyclohexadienones.
Carbonate on polymer is a valuable solid supported reagent (SSR) to promote, under eco‐friendly conditions, the preparation of 2H‐1,4‐benzoxazin‐2‐one derivatives starting from β‐nitroacrylates and aminophenols via a domino process. 相似文献
The first example of a β‐isocupreidine (β‐ICD)‐catalyzed highly enantioselective [2+2] annulation of allenoates with trifluoromethyl ketones has been disclosed, allowing the synthesis of optically active 2‐alkyleneoxetanes in moderate to good yields along with good to high enantioselectivities and high diastereoselectivities. Further transformations of the cycloadducts have been also disclosed to afford biologically interesting 6‐trifluoromethyl‐5,6‐dihydropyran‐2‐ones and trifluoromethyl β‐keto acids in good yields. 相似文献
A highly diastereo‐ and enantioselective conjugate addition of α‐substituted cyanoacetates to maleimides in the presence of a chiral bifunctional thiourea‐tertiary amine catalyst has been investigated for the first time. The procedure was capable of tolerating a relatively wide range of substrates with respect to α‐substituted cyanoacetates and maleimides, providing a series of substituted succinimidates bearing two vicinal quaternary‐tertiary stereocenters in excellent yields (up to 97%) with excellent diastereo‐ (up to 98:2) and enantioselectivities (up to 98%) under mild reaction conditions. 相似文献
A convenient organocatalytic enantioselective decarboxylative Michael addition of β‐keto acids to dicyanoolefins and disulfonylolefins is realized. In the presence of saccharide‐derived chiral amino thioureas, the reaction proceeded smoothly to afford a wide range of the Michael adducts in 62–99% yield with 70–94% ee. Moreover, one of the chiral adducts obtained could be readily converted into the monofluorinated product in a total 68% yield over four steps with 85% ee.
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
Silver‐catalyzed three‐component, tandem reactions of 4‐alkynyl‐2‐oxo‐2H‐chromene‐3‐carbaldehydes, amines and various nucleophiles result in the formation of highly functionalized chromeno[3,4‐c]pyridin‐5‐ones in high yields. Gold‐catalyzed [4+2] cycloadditions of 4‐alkynyl‐2‐oxo‐2H‐chromene‐3‐carbaldehydes with alkynes or alkenes have also been achieved to afford benzo[c]chromen‐6‐ones efficiently.
A facile one‐pot, catalyst‐free reaction has been developed for the synthesis of 2,3,6,7‐tetrahydro‐1H‐pyrrolo[3,2‐c]pyridin‐4(5H)‐ones from readily available 1‐acryloyl‐1‐N‐arylcarbamylcyclopropanes and amines using a domino ring‐opening/cyclization/aza‐addition sequence.
The catalytic asymmetric [4+2] annulations of isatins with but‐3‐yn‐2‐one catalyzed by the Cinchona alkaloids‐derived oragnocatalyst (DHQD)2PHAL have been developed in the presence of 3.0 equivalents of D ‐diethyl tartrate in the mixed solvent (diphenyl ether/diethyl ether=1/1) or a slightly modified one, affording the corresponding substituted spiro[indoline‐3,2′‐pyran]‐2,4′(3′H)‐diones in good to excellent yields with high enantioselectivities under mild conditions.
An efficient strategy for a high‐yielding and stereoselective synthesis of α‐trifluoromethyl unsaturated carboxylic acids directly from the reactions of 3,3,3‐trifluoropropanoic acid (CF3CH2COOH) with various aryl aldehydes in the presence of titanium tetrachloride (TiCl4) is reported here for the first time, which is a valuable expansion for the classical Knoevenagel reaction. Because these compounds may have potential applications in organic electronics and can be easily converted to the corresponding fluorinated alcohols and amino acids with excellent bioactivity, this route should be a good choice for the preparation of α‐trifluoromethyl‐containing derivatives. 相似文献
A collection of 4‐(C‐galactosyl)‐ and 4‐(C‐ribosyl)‐β‐lactams featuring different substituents at C‐3 and N‐1 was prepared by combining in a one‐pot procedure a formyl C‐glycoside, a primary amine, and a substituted acetyl chloride in the presence of base (Staudinger‐type reaction). Sulfonyl chloride and aminomethylated resins were used in sequence to remove excess of components and by‐products. Two pure C‐glycosyl‐β‐lactams were effectively transformed into C‐glycosyl‐N‐Boc‐β‐amino‐α‐hydroxy esters (C‐glycosyl isoserines) and a C‐ribosyl dipeptide via base‐promoted heterocycle ring opening by methanol and L ‐phenylalanine methyl ester, respectively. 相似文献