Abstract
The 1,3-dipolar cycloaddition reaction of alkenes with nitrones was catalyzed by Yb(OTf) 3 or Sc(OTf) 3 giving isoxazolidines in high yields and selectivities. The catalyst Yb(OTf) 3 induce a high endo-selectivity in the reaction of up to 94% de, whereas Sc(OTf) 3 show the highest rate accelerations. Both the conversion and endo-selectivity of the Yb(OTf) 3 and Sc(OTf) 3 catalyzed reactions proved to be dependent on the amount and type of molecular sieves added. The application of different chiral ligands in 1,3-dipolar cycloaddition reactions of a series of alkenes with nitrones catalyzed by Yb(OTf) 3 or Sc(OTf) 3 has been studied and it was found that high endo-selectivities and an ee's of up to 73% could be obtained by the use of Yb(OTf) 3 and 2,6-bis[4(S)-isopropyl-2-oxazolidin-2-yl]pyridine (PyBOX) as the chiral ligand.
Published Version
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