Isothiourea-catalysed enantioselective Michael addition of N-heterocyclic pronucleophiles to α,β-unsaturated aryl esters
作者:Chang Shu、Honglei Liu、Alexandra M. Z. Slawin、Cameron Carpenter-Warren、Andrew D. Smith
DOI:10.1039/c9sc04303a
日期:——
The isothiourea-catalysed enantioselective Michaeladdition of 3-aryloxindole and 4-substituted-dihydropyrazol-3-one pronucleophiles to α,β-unsaturated p-nitrophenyl esters is reported. This process generates products containing two contiguous stereocentres, one quaternary, in good yields and excellent enantioselectivities (>30 examples, up to > 95 : 5 dr and 99 : 1 er). This protocol harnesses the
Chiral iminophosphorane catalyzed asymmetric sulfenylation of 4-substituted pyrazolones
作者:Jianwei Han、Yanxia Zhang、Xin-Yan Wu、Henry N. C. Wong
DOI:10.1039/c8cc09049a
日期:——
An excellent level of enantioselectivity in asymmetric sulfenylation of 4-substituted pyrazolones was achieved with chiral iminophosphorane as the organocatalyst under continuum solvation conditions (up to 99% ee). Importantly, this catalytic process features high efficiency with excellent enantioselectivities, easy separation of products, low catalytic loadings and scale-up to grams without loss of
MICROWAVE-ASSISTED SYNTHESIS OF SUBSTITUTED PYRAZOLONES UNDER SOLVENT-FREE CONDITIONS
作者:Mohammad M. Mojtahedi、Mohammad R. Jalali、M. Saeed Abaee、Mohammad Bolourtchian
DOI:10.1515/hc.2006.12.3-4.225
日期:2006.1
synthetic targets (3). A number of known methods have been documented in the literature for the synthesis of pyrazolones. Most of these methods are based on the reaction of a hydrazine derivative with a ß-keto ester in a solvent under refluxing conditions (4). Recent developments include solid-phase synthesis of substituted pyrazolones from polymer-bounded ß-keto esters (5) and a two-step reaction of
Pd-Catalyzed Asymmetric Allylic Alkylation of Pyrazol-5-ones with Allylic Alcohols: The Role of the Chiral Phosphoric Acid in C–O Bond Cleavage and Stereocontrol
作者:Zhong-Lin Tao、Wen-Quan Zhang、Dian-Feng Chen、Arafate Adele、Liu-Zhu Gong
DOI:10.1021/ja402740q
日期:2013.6.26
The combination of a palladium complex with a chiral phosphoramidite ligand and a chiral phosphoric acid enables the first highly efficient asymmetricallylic alkylation of pyrazol-5-ones with allylicalcohols, affording multiply functionalized heterocyclic products in high yields with excellent enantioselectivities that would be of great potential in the synthesis of pharmaceutically interesting molecules
Highly Enantioselective Michael Addition of Pyrazolin-5-ones Catalyzed by Chiral Metal/N,N′-Dioxide Complexes: Metal-Directed Switch in Enantioselectivity
Make the switch: The first example of a switch in enantioselectivity in the asymmetric Michaeladdition of pyrazolin‐5‐ones to 4‐oxo‐4‐arylbutenoates that is controlled by the metal center of the catalyst is reported. By using the same N,N′‐dioxide ligand L with different metals the respective enantiomers of various 4‐substituted 5‐pyrazolone derivatives were obtained. Tf=trifluoromethanesulfonyl.