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%
Asymmetric Michael/Aromatization Reaction of Azlactones to α,β-Unsaturated Pyrazolones with C-4 Regioselectivity Catalyzed by an Isosteviol-Derived Thiourea Organocatalyst
作者:Zhi-Cong Geng、Xiang Chen、Jin-Xin Zhang、Ning Li、Jian Chen、Xiao-Fei Huang、Shao-Yun Zhang、Jing-Chao Tao、Xing-Wang Wang
DOI:10.1002/ejoc.201300524
日期:2013.8
activities. Herein, heterocyclic compounds containing both a pyrazole motif and a masked amino acid structure are synthesized through the asymmetricMichael/aromatization of azlactones to α,β-unsaturatedpyrazolones by using isosteviol-derived amine thiourea as the organocatalyst. The products are obtained in good yields (up to 93 %) with good diastereoselectivities and good enantioselectivities (up to >10:1 dr
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。
An efficient and highly diastereoselective synthesis of carbocyclic spiropyrazolones via one-pot sequential dual organo-silver catalyzed Michael-hydroalkylation reactions
作者:Khyati Shukla、Sadhna Shah、Nirmal K. Rana、Vinod K. Singh
DOI:10.1016/j.tetlet.2018.11.064
日期:2019.1
An economical approach for the diastereoselective synthesis of highly functionalized carbocyclic spiropyrazolone derivatives having one quaternary and two tertiary stereocenters along with one exocyclic double bond exploiting dual organo-silver sequential catalysis has been developed. The unified method to both cyclohexyl and cyclopentyl spirocompounds involves the reaction of γ- and β-nitroalkynes
Asymmetric Synthesis of Spiropyrazolones via Chiral Pd(0)/Ligand Complex-Catalyzed Formal [4+2] Cycloaddition of Vinyl Benzoxazinanones with Alkylidene Pyrazolones
In the presence of the chiral Pd(0)/ligand complex, vinyl benzoxazinanones underwent the [4+2] cycloaddition with alkylidene pyrazolones smoothly and delivered spiropyrazolones in reasonable yields, diastereoselectivities, and eneantioselectivities (up to >99% yield, >99:1 dr and 99% ee). The absolute configuration of the obtained spiropyrazolones was unambiguously characterized with the use of X-ray