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[Carbon-carbon bond formation based on alkenylphosphonates]
1Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan.
Yakugaku Zasshi : Journal of the Pharmaceutical Society of Japan
|December 1, 2001
Summary
Researchers developed new methods for synthesizing axial chiral allenes using conjugate addition and Horner-Wadsworth-Emmons reactions. These advancements enable efficient allene synthesis and the creation of novel chiral phosphine ligands.
Area of Science:
- Organic synthesis
- Asymmetric catalysis
- Organophosphorus chemistry
Context:
- Development of asymmetric conjugate addition reactions using lithium thiolates, organolithiums, and organocopper reagents.
- Establishment of an efficient asymmetric Horner-Wadsworth-Emmons (HWE) reaction.
- Exploration of synthetic routes towards axial chiral allenes.
Purpose:
- To synthesize axial chiral allenes by combining conjugate addition and HWE reactions.
- To develop novel cyclization reactions of alkenylphosphonates for creating complex organic structures.
- To apply developed synthetic methods for the preparation of chiral phosphine ligands.
Summary:
- A Michael-aldol reaction of alkenylphosphonates with aldehydes, followed by treatment with potassium hydride (KH), directly yields alpha,beta-unsaturated hydroxyphosphonates convertible to allenes.
- Allenes are synthesized via a sequential double HWE reaction in one flask, utilizing a key metal exchange from lithium to potassium alkoxide.
- A selective cyclization of bisalkenylphosphonates using lithium diisopropylamine (LDA) yields deprotonation-cyclization products, applicable to chiral phosphine ligand synthesis.
Impact:
- Provides efficient synthetic routes to axial chiral allenes.
- Expands the utility of alkenylphosphonates in carbon-carbon bond formation.
- Enables the synthesis of valuable chiral phosphine ligands for asymmetric catalysis.