A chiral N-heterocyclic carbene (NHC)-catalyzed [4 + 2] annulation of γ-chloroenals and α-arylidene pyrazolinones was developed in the absence of expensive oxidants. The reaction proceeds smoothly via a vinyl enolate intermediate to afford spirocyclohexane pyrazolones in moderate to good yield (up to 86%) with high diastereoselectivities (up to 15:1 dr) and excellent enantioselectivities (up to >99%
Optically Active 4-Substituted 5-Nitropentan-2-ones: Valuable Chiral Building Blocks for the Stereocontrolled Construction of Spiro-Pyrazolone Scaffolds with Five Contiguous Stereogenic Centers
作者:Jiao Sun、Cuiping Jiang、Zhenghong Zhou
DOI:10.1002/ejoc.201501449
日期:2016.2
The application of readily available opticallyactive4-substituted5-nitropentan-2-ones as chiralbuildingblocks in the stereocontrolledconstruction of spiro-pyrazolonescaffolds was investigated. In the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (1 equiv.) opticallyactive4-substituted 5-nitropentan-4-ones exhibited excellent chiral inducing abilities in the diastereoselective cascade Michael/aldol
The Regiocontrollable Enantioselective Synthesis of Chiral Trifluoromethyl-Containing Spiro-Pyrrolidine-Pyrazolone Compounds via Amino-Regulated 1,3-Proton Migration Reaction
as catalyst, the 1,3-dipolar cycloaddition of α,β-unsaturated pyrazolone with diethyl2-((2,2,2-trifluoroethyl)imino) malonate offered adducts in excellent yields, dr, and ee. While the cyclohexanediamine-derived squaramide was employed, the reaction afforded a series of structure isomers through a switched umpolung reaction.
描述了含CF 3的螺-吡咯烷-吡唑啉酮化合物的氨基控制区域发散不对称合成。以生物碱衍生的方酸酰胺为催化剂,α,β-不饱和吡唑啉酮与 2-((2,2,2-三氟乙基)亚氨基)丙二酸二乙酯的 1,3-偶极环加成反应以优异的收率、dr 和 ee 提供加合物。虽然使用了环己二胺衍生的方酸酰胺,但该反应通过转换的 umpolung 反应提供了一系列结构异构体。
A PPh<sub>3</sub>-catalyzed sequential annulation reaction to construct cyclopentane-fused dihydropyrazolone-pyrrolidinediones
作者:Cheng Cheng、Xiaobin Sun、Zhiwei Miao
DOI:10.1039/d0ob00815j
日期:——
An effective strategy for the synthesis of cyclopentane-fused dihydropyrazolone-pyrrolidinediones via a PPh3-catalyzed sequential annulation reaction of maleimides and unsaturated pyrazolones has been developed.
Diastereo- and Enantioselective Synthesis of Spiro-Pyrrolidine-Pyrazolones by Squaramide-Catalyzed Cascade Aza-Michael/Michael Reactions
作者:Jun-Hua Li、Hongliang Wen、Lei Liu、Da-Ming Du
DOI:10.1002/ejoc.201600316
日期:2016.5
new method was developed to rapidly generate a series of spiro-pyrrolidine-pyrazolones by using a squaramide-catalyzedcascade aza-Michael/Michael addition of either tosylaminomethyl enones or enoates to unsaturated pyrazolones. This tandem reaction sequence proceeded well by using 5 mol-% of a chiral bifunctional tertiary amine squaramide catalyst to afford the desired products in good to excellent