The 1,3-Dipolar Cycloaddition of 3-Methyl-5-phenylisoxazoline N-Oxides

The title isoxazoline N-oxide underwent 1,3-dipolar cycloaddition with a number of electron deficient olefins regiospecifically to give isoxazolizidines. All four possible geometric approaches of addenda leading to successful cycloadditions occurred to give mixtures of products. A pressure at 1-2 KBar did accelerate the rate of the 1,3-dipolar cycloadditions significantly without improving the selectivity of geometrical orientations of approaches: the poor selectivity was ascribed to the lack of ground state molecular association in solution