Synthesis of 2-isoxazolines from olefins derived from norephedrine and pulegone

In this communication we report the use of (±)-norephedrine and (−)-8-benzylaminomenthol (derived from (+)-pulegone) as chiral adjuvants for the cycloaddition of α,β-unsaturated 1,3-dipolarophiles. 2-Isoxazolines were obtained with low stereoselectivity from the reaction of nitrile oxides with the N-tosyl norephedrine derivative as the dipolarophile. Cycloaddition of nitrile oxide with 2-vinyl-N-benzyl-4,4,7α-trimethyl-trans-octahydro-1,3-benzoxazine produced stereoisomeric 2-isoxazolines in a ratio of about 95:5.