Abstract
A regio-, diastereo- and enantioselective 1,3-dipolar cycloaddition reaction between nitrones and electron-deficient alkenes has been developed employing C1-symmetrical Ti(OTos)2- and TiCl2-TADDOLate as catalysts. In the presence of powdered 4 Å molecular sieves and 100 mol% of Ti(OTos)2-TADDOLate as the catalyst, the nitrones smoothly react with alkenes at room temperature to give isoxazolidines in high conversion, giving the trans-diastereomer of the isoxazolidines with de's up to >90% and ee up to 58%. Furthermore, C1-symmetrical TiCl2-TADDOLate has a better chiral induction, giving the trans-diastereomer of the isoxazolidines with high enantioselectivity up to 70% ee. The influence of catalyst amount, temperature and solvents on the reaction course has been investigated