| Summary: | 碩士 === 國立中興大學 === 化學系所 === 102 === The synthesis of enantio-enriched propargylic alcohols has been intensely researched in asymmetric synthesis due to the usefulness of propargylic alcohol as versatile building blocks for a large number of pharmaceutically important molecules and natural products.
In this work, we had synthesized a series of camphor-derived chiral ligands. Compound 41 could act as a ligand for Ti(OiPr)4 to catalyze the asymmetric addition of phenylacetylene to benzaldehyde to give an
enantioselectivity of 51%. The poor e.e. was significantly increased from 51% to 85% by changing the ligand (41 to 43c) and reaction temperature (rt to –20 °C).
The structure of 43 reveals a pocket on the side of the sulfonyl oxygen bond. Since the Ti-O (sulfonyl) bond is very weak, the benzaldehyde is expected to access the six-coordinate metal center from the bottom of the pocket for replacing the sulfonyl oxygen donor. Apparently, this pocket locks the aldehydes into suitable position for achieving good enantioselectivity.
In this study, cheap and readily available starting material and simple synthetic pathway were used to furnish effective chiral ligand, 43c, for the asymmetric alkyne addition to aldehydes. A useful system for preparing
chiral propargylic alcohols in high yields (55–99%) and medium to excellent e.e. has been developed (62–99%).
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