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%
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
Enantioselective Synthesis of Unsymmetrical Diaryl-Substituted Spirocyclohexanonepyrazolones through a Cascade [4+2] Double Michael Addition
作者:Jin-Xin Zhang、Nai-Kai Li、Zhao-Min Liu、Xiao-Fei Huang、Zhi-Cong Geng、Xing-Wang Wang
DOI:10.1002/adsc.201200925
日期:2013.3.11
ortho‐fluorobenzoic acid is an efficient catalyst system for the doubleMichaeladdition of arylidenepyrazolones with α,β‐unsaturated ketones, providing chiral unsymmetrical 6,10‐diaryl‐substituted spiro[cyclohexanone‐pyrazolone] derivatives in high yields (up to 98%) with good diastereoselectivities and excellent enantioselectivities (up to 88:12 dr, 99% ee).
yield (up to 98%) and high enantioselectivity (up to 97% ee) via vinylogous Michaelreaction/cyclization cascadereaction of α‐arylidene pyrazolones and α,α‐dicyanoalkylidenes. The formal [4+2] atom‐economical annulation proceeds with commercially available Takemoto's catalyst under mild reaction conditions. Scale‐up reaction and post‐transformation of the products were also demonstrated.
Asymmetric Synthesis of Bispiro[γ-butyrolactone-pyrrolidin-4,4′-pyrazolone] Scaffolds Containing Two Quaternary Spirocenters via an Organocatalytic 1,3-Dipolar Cycloaddition
Enantiomerically enriched bispiro[γ‐butyrolactone‐pyrrolidin‐4,4′‐pyrazolone] skeletons were synthesized firstly through a simple organocatalytic 1,3‐dipolarcycloaddition reaction between α‐imino γ‐lactones and alkylidene pyrazolones, which afforded a diversity of bispirocyclic scaffolds in high yields and excellent diastereo‐ and enantioselectivities.