Stereochemical studies. 58 . Saturated heterocycles. 39 . Preparation and steric structures of dihydro‐1,3‐oxazines, 1,3‐oxazin‐2‐ones and 1,3‐oxazine‐2‐thiones fused with norbornane and norbornene

3‐ endo ‐Aminobicyclo[2.2.1]hept‐5‐ene‐2‐ endo ‐carboxylic acid ( 1 ), prepared from endo ‐norborn‐5‐ene‐2,3‐dicarboxylic acid anhydride, and the analogous saturated cis‐exo ‐amino acid ( 3 ) were reduced with lithium aluminum hydride to the aminoalcohols 2 and 4 ; the latter were cyclized by means of arylimino ethers to methylene‐bridged tetrahydro‐ ( 6a‐c ) and hexahydro‐3,1‐benzoxazines ( 7b‐d ), respectively. The endo ( 2 ) and exo ( 4 ) aminoalcohols were converted to methylene‐bridged tetrahydro‐3,1‐benzoxazin‐2‐one ( 9 ) and hexahydro‐3,1‐benzoxazin‐2‐one ( 12 ) with ethyl chloroformate and sodium methoxide; treatment of the alcohols with carbon disulfide gave, via the dithiocarbamates, the corresponding 2‐thiones ( 11, 13 ). The structures were confirmed by ir and nmr spectroscopy.