2-Vinyl-trans-octahydro-1,3-benzoxazine: Cyclization and 1,3-dipolar cycloaddition of nitrile oxides

Article abstract of DOI:10.1016/S0040-4039(98)02061-9

A study of the stereochemistry of the acid-catalyzed cyclization between (-)-8-tosylaminomenthol (derived from (+)-pulegone) and acrolein diethyl acetal afforded two novel chiral perhydro-1,3-benzoxazine isomers 4a and 4b. Catalyst type as well as the reaction conditions dramatically affected the isomeric ratio. An X-ray crystal structure of 4a established a chair-boat conformation. The usefulness of this auxiliary was demonstrated by highly diastereoselective (i.e. 90% de) 1,3-dipolar cycloadditions with nitrile oxides.