2-Vinyl-trans-octahydro-1,3-benzoxazine: Cyclization and 1,3-Dipolar Cycloaddition of Nitrile Oxides.

Abstract 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.