Showing papers by "Xiaohua Liu published in 2012"
TL;DR: In this paper, a minireview introduces the recent application of rare earth (RE) metal complex catalysts in the synthesis of targeted frameworks, together with direct addition reactions of 3-substituted oxindoles or isatins.
Abstract: The enantioselective synthesis of 3-functionalized oxindole derivatives has experienced an explosive development. This minireview introduces the recent application of rare earth (RE) metal complex catalysts in the synthesis of targeted frameworks. The direct addition reactions of 3-substituted oxindoles or isatins are described, together with a discussion of the catalytic mechanism and related transformations to pharmaceuticals.
372 citations
TL;DR: Catalytic enantioselective Baeyer-Villiger oxidations of racemic and meso cyclic ketones achieved in the presence of chiral N,N'-dioxide-Sc(III) complex catalysts afforded series of optically active ε- and γ-lactones in up to 99% yield and 95% ee.
Abstract: Catalytic enantioselective Baeyer–Villiger (BV) oxidations of racemic and meso cyclic ketones were achieved in the presence of chiral N,N′-dioxide–ScIII complex catalysts. The BV oxidations of prochiral cyclohexanones and cyclobutanones afforded series of optically active e- and γ-lactones, respectively, in up to 99% yield and 95% ee. Meanwhile, the kinetic resolution of racemic 2-arylcyclohexanones was also realized via an abnormal BV oxidation. Enantioenriched 3-aryloxepan-2-ones, whose formation is counter to the migratory aptitude, were obtained preferentially. Both the lactones and the unreacted ketones were obtained with high ee values.
128 citations
TL;DR: Highly functionalized 2-quinolone derivatives containing a chiral C4-quaternary stereocenter were obtained in high yields and high levels of selectivity under mild reaction conditions.
Abstract: Asymmetric expansion: A catalytic asymmetric ring-expansion reaction of the title compounds occurs in the presence of a Sc(OTf)(3) catalyst bearing an N,N'-dioxide-based ligand. Highly functionalized 2-quinolone derivatives containing a chiral C4-quaternary stereocenter were obtained in high yields and high levels of selectivity under mild reaction conditions (see scheme; Tf=trifluoromethanesulfonyl).
101 citations
TL;DR: The asymmetric direct vinylogous Michael reaction of α,β-unsaturated γ-butyrolactams with alkylidene malonates has been developed using a novel bifunctional C(1)-symmetric guanidine organocatalyst embodied a secondary amine subunit.
78 citations
TL;DR: A simple chiral diamine catalyst was successfully applied in the asymmetric Michael reaction between cyclic dimedone and α,β-unsaturated ketones and the desired adducts were obtained in high yields with excellent enantioselectivities.
Abstract: A simple chiral diamine catalyst (1a) was successfully applied in the asymmetric Michael reaction between cyclic dimedone and α,β-unsaturated ketones. Both acyclic enones with aryl or alkyl β-substituents and cyclic enones were tolerated well in the reaction. The desired adducts were obtained in high yields (up to 98%) with excellent enantioselectivities (up to 97% ee). The additives were found to increase the reactivity dramatically. The biologically active 2,4-disubstituted polyhydroquinoline scaffold was conveniently prepared through an ammoniation from the generated 3,4-dihydropyran product.
51 citations
22 citations
TL;DR: In this paper, the mechanism of the aminolysis of meso-epoxides catalyzed by the proline-based N,N′-dioxide-indium tris(triflate) complex was performed using control experiments, UV-Vis spectroscopy, 1H NMR, electrospray ionization mass spectrometry (ESI-MS) and scanning electron microscopy (SEM).
Abstract: An exploration of the mechanism of the aminolysis of meso-epoxides catalyzed by the proline-based N,N′-dioxide-indium tris(triflate) complex was performed using control experiments, UV-Vis spectroscopy, 1H NMR, electrospray ionization mass spectrometry (ESI-MS) and scanning electron microscopy (SEM). Control experiments disclosed that the ligand-to-indium tris(triflate) ratio, the catalyst loading, the concentration, and the presence of 4 A MS have dramatic effects on this reaction with regard to both the yield and the enantioselectivity. Combined with control experiments, UV-Vis spectroscopy, 1H NMR, ESI-MS and SEM analyses revealed that molecular sieves perform multiple functions in the catalysis. A plausible molecular sieves-assisted reaction pathway was proposed. In this pathway, molecular sieves perform (i) as desiccant to in situ dry the reaction system, (ii) as proton transfer agent to accelerate the catalysis, and (iii) as counter ion source to preserve the electroneutrality of the transition states. Besides, the generality of the substrate scope was further explored; excellent yields (up to 99%) and enantioselectivities (up to 99% ee) were obtained.
16 citations
TL;DR: The catalyst system efficiently promotes the asymmetric addition of enones to cyclic 1,3-diones to form chromenone derivatives like (III and (VI) and the anticoagulant warfarin (VIII) as discussed by the authors.
Abstract: The catalyst system efficiently promotes the asymmetric addition of enones to cyclic 1,3-diones to form chromenone derivatives like (III) and (VI) and the anticoagulant warfarin (VIII).
3 citations
TL;DR: In this paper, the reaction occurs in the presence of an N,N′-dioxide-scandium complex generated in situ under mild conditions, and the reaction is described in detail.
Abstract: The reaction occurs in the presence of an N,N′-dioxide—scandium complex generated in situ under mild conditions.
2 citations
TL;DR: In this article, a minireview introduces the recent application of rare earth (RE) metal complex catalysts in the synthesis of targeted frameworks, together with direct addition reactions of 3-substituted oxindoles or isatins.
Abstract: The enantioselective synthesis of 3-functionalized oxindole derivatives has experienced an explosive development. This minireview introduces the recent application of rare earth (RE) metal complex catalysts in the synthesis of targeted frameworks. The direct addition reactions of 3-substituted oxindoles or isatins are described, together with a discussion of the catalytic mechanism and related transformations to pharmaceuticals.
2 citations
TL;DR: The reaction of ortho-hydroxy aldimines with azlactones proceeds with excellent trans-selectivity when AGU is used as catalyst as discussed by the authors, and the reaction is shown to be transselective with AGU as a catalyst.
Abstract: The reaction of ortho-hydroxy aldimines with azlactones proceeds with excellent trans-selectivity when AGU is used as catalyst.
TL;DR: Chiral 2-substituted-1,5-benzodiazepine derivatives were synthesized for the first time from an enantioselective domino reaction involving o-phenylenediamine and 2′-hydroxychalcones as mentioned in this paper.
Abstract: Chiral 2-substituted-1,5-benzodiazepine derivatives were synthesized for the first time from an enantioselective domino reaction involving o-phenylenediamine and 2′-hydroxychalcones. The titanium complex formed from chiral ligand 1a derived from (S)-BINOL and L-prolineamide promoted the reaction and gave the products in good yields with up to 82 % ee.
TL;DR: In this article, a bifunctional guanidine catalyst was proposed and successfully applied in the asymmetric direct vinylogous Michael reaction of lactam (I) with malonates (II).
Abstract: A novel bifunctional guanidine catalyst is prepared and successfully applied in the asymmetric direct vinylogous Michael reaction of lactam (I) with malonates (II).