Diastereoselective synthesis of 2,3,4,5-tetrasubstituted isoxazolidines via 1,3-dipolar cycloaddition

The 1,3-dipolar cycloaddition reactions of α-2-methoxyaryl nitrones with nitrostyrenes and chalcones have been investigated. The regiochemistry and stereochemistry of the resultant cycloadducts have been determined with the help of NMR spectroscopy and X-ray analysis. β-Nitrostyrenes add to nitrones to give two geometrical isomers, while the β-methyl-β-nitrostyrene gives a single isomer in relatively low yield. The chalcones give a single cycloadduct upon 1,3-dipolar addition.