RESUMEN
An organocatalyzed asymmetric Mannich reaction of pyrazoleamides and cyclic trifluoromethyl ketimines with a chiral bifunctional amine-squaramide as the catalyst was developed. A wide range of trifluoromethyl dihydroquinazolinone derivatives bearing adjacent quaternary and tertiary stereogenic centers were readily obtained in good to excellent yields (up to 99%) with high diastereo- and enantioselectivities (up to 99% ee and >20 : 1 dr). The large scale experiment and transformation of the product have also been demonstrated.
RESUMEN
A base-mediated Neber reaction of enaminopyrazolones, which are the tautomers of 4-acyloxime-2-pyrazolin-5-ones, with sulfonyl chlorides was achieved. With this developed approach, a range of spiro-fused 2H-azirine-pyrazolones were obtained in good yields under mild conditions. A preliminary trial of a catalytic asymmetric version of the Neber reaction was conducted and gave promising enantioselectivity.
RESUMEN
The asymmetric Neber reaction of 3-O-sulfonyl ketoxime, in situ generated from isatin ketoxime and sulfonyl chloride, for the synthesis of chiral spirocyclic oxindole compounds is reported. With the developed protocol, a range of chiral spirooxindole 2H-azirines could be obtained in good to excellent yields and up to a 92 : 8 enantiomeric ratio by using (DHQD)2PHAL as the catalyst. This methodology is the only example of the catalytic asymmetric construction of spirooxindole 2H-azirine compounds.
Asunto(s)
Azirinas/química , Azirinas/síntesis química , Compuestos de Espiro/química , Catálisis , Técnicas de Química Sintética , EstereoisomerismoRESUMEN
An organocatalyzed direct asymmetric vinylogous Michael addition reaction of α,ß-unsaturated γ-butyrolactam to 2-enoylpyridines has been developed with a chiral bifunctional amine-squaramide as the catalyst. This approach provides easy access to a series of optically active α,ß-unsaturated γ-substituted butyrolactams in high yields (up to 99%) with excellent diastereoselectivities (up to >99 : 1) and enantioselectivities (up to >99% ee).
RESUMEN
For the first time, a catalytic asymmetric Henry reaction of 1H-pyrrole-2,3-diones was achieved with a chiral bifunctional amine-thiourea as a catalyst possessing multiple hydrogen-bond donors. With this developed method, a range of 3-hydroxy-3-nitromethyl-1H-pyrrol-2(3H)-ones bearing quaternary stereocenters were obtained in acceptable yield (up to 75%) and enantioselectivity (up to 73% ee).
RESUMEN
Enantioselective Michael/cyclization cascade reactions of 3-hydroxyoxindoles/3-aminooxindoles with α,ß-unsaturated acyl phosphonates by using a cinchonine derived squaramide as the catalyst were developed. A broad range of spirocyclic oxindole-γ-lactones/lactams could be obtained in moderate to excellent yields (up to 98%) with good to excellent diastereo- and enantioselectivities (up to >99:1 dr and 97% ee) under mild conditions. This work represents the first example about the α,ß-unsaturated acyl phosphonates for the asymmetric construction of spirocyclic oxindoles.
RESUMEN
Organocatalytic asymmetric dearomatization of 3-nitroindoles and 3-nitrobenzothiophenes by reaction with ethyl 4-mercapto-2-butenoate has been developed. A range of chiral tetrahydrothiopheneindolines and tetrahydrothiophenebenzothiophenes bearing three contiguous stereocenters are obtained in high yields with good diastereoselectivities and excellent enantioselectivities. This is the first example of thiol-triggered catalytic asymmetric dearomatization of 3-nitroindoles and 3-nitrobenzothiophenes.
RESUMEN
A method for the enantioselective construction of hydrocarbazole skeletons through dearomative [4 + 2] annulation of 3-nitroindoles with Nazarov reagents is reported. The reactions use multiple hydrogen-bonding bifunctional thiourea as catalyst and are highly diastereo- and enantioselective (up to >20:1 dr and >99% ee). The protocol was demonstrated by preparative-scale experiment and the versatile conversion of the products. The multiple hydrogen-bonding in the catalyst plays a pivotal role in the reactivity and stereoselectivity.
RESUMEN
A highly diastereo- and enantioselective [3+2] cycloaddition reaction of N-2,2,2-trifluoroethylisatin ketimines and 3-alkenyl-5-arylfuran-2(3H)-ones was developed with 1 mol% thiourea-tertiary amine as the catalyst. A series of spiro[pyrrolidin-3,2'-oxindoles] bearing four consecutive stereocenters, including two vicinal spiro-quaternary chiral centers, were efficiently obtained with excellent results (up to >99% yield, >20 : 1 dr, and >99% ee).
RESUMEN
The diastereo- and enantioselective direct vinylogous Michael addition reaction of γ-substituted butenolides to 2-enoylpyridines has been achieved. A range of γ,γ-disubstituted butenolide derivatives, bearing two consecutive tri- and tetrasubstituted stereogenic centers, were readily obtained in good yields with excellent stereoselectivities (up to >99 : 1 dr and >99% ee).
Asunto(s)
4-Butirolactona/análogos & derivados , 4-Butirolactona/síntesis química , Ciclobutanos/síntesis química , Piridinas/síntesis química , 4-Butirolactona/química , Catálisis , Ciclobutanos/química , Estructura Molecular , Piridinas/química , EstereoisomerismoRESUMEN
An unprecedented organocatalytic asymmetric Michael/cyclization cascade reaction of 3-isothiocyanato oxindoles and 3-nitroindoles has been disclosed. A wide range of enantioenriched polycyclic spirooxindoles, containing three contiguous chiral centers with two of them having quaternary stereocenters, could be smoothly obtained with satisfactory results (up to 99% yield, >99:1 dr, and 96% ee). This method is very promising because the reaction is scalable, and the versatile transformations of the products into other spirocyclic oxindoles are also feasible.