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Organocatalytic Methodplogy Research for Constructing Multi-Chiral Carbonrings、Nitrogen Heterocycles and Spiropyrazolones

Author: LiangJinYan
Tutor: WangRui
School: Lanzhou University
Course: Biochemistry and Molecular Biology
Keywords: asymmetric catalysis Michael addition reaction chiral drugs pyrazolones Jorgensen-Hayashi catalyst cinchona alkaloid cascade reaction
CLC: O621.36
Type: PhD thesis
Year: 2012
Downloads: 108
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Abstract


Subunits containing carbonrings、nitrogen heterocycles and spirocyclic structures are common in biologically active molecules. Therefore, it is a big challenge for chemists to construct these complicated buildings. During the past decades, the operational simplicity, ready availability of these mostly inexpensive bench-stable organocatalysts, which are incomparably more robust than enzymes or other bioorganic catalysts makes organocatalysis an attractive method for the synthesis of complex structures. In this context, we try to search new methods of organocatalysis to achieve above cyclic structures.Michael addition reaction is one of the most important carbon-carbon bond-forming reactions, which can provide many important precursors in organic synthesis. Synthesis and applications of high active and selective organic small molecule catalysts is a hot research field of asymmetric organic synthesis. Based on the imine-enamine activation mode, imine-imine activation mode and enamine-imine activation mode, we designed three different Michael addition cascade reactions to obtain functionalized carbonrings, nitrogen heterocycles and spirocyclic structures with high enantioselectivities.This dissertation includes four sections:In the first part, the recent progress of organocatalytic Michael addition reaction and Michael addition cascade reaction has been summarized;In the second part, an organocatalytic double Michael addition reactions of functionalized nitro-compounds and unsaturated aldehyde has been developed. The progress is promoted by a readily prepared Jorgensen-Hayashi catalyst and affords a series of four stereocenters hexanes derivatives.In the third part, we developed an organocatalytic asymmetric tandem Michael/Aza-Aldol reaction of2-formylamidomalonates with α,β-unsaturated aldehydes. The simple and practical process, based on co-catalysis platform of acid and base, affords synthetically useful chiral hemiaminals which can be converted into y-butyrolactams in good yields and with excellent enantioselectivities. Moreover, various dihydropyrroles and proline analogues can also be obtained from the intermediates.In the fourth part, The first organocatalytic double Michael cascade reaction between unsaturated ketones and unsaturated pyrazolones has been developed which provides spiropyrazolones core structures containing two interval or three consecutive stereogenic centers with excellent diastereo-(>20:1) and enantioselectivities (up to99%ee). Moreover, a pair of enantiomers can be achieved via different catalysis.

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CLC: > Mathematical sciences and chemical > Chemistry > Organic Chemistry > Organic Chemistry general issues > Synthetic organic chemistry > Heavy organic synthesis or catalytic organic synthesis
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