Stereochemical studies—XXXVII: Saturated heterocycles—XIII Configuration and conformation of Z‐ and E‐N‐methyl‐ and ‐N‐ benzyl‐2‐p‐nitrophenyl‐4,5‐ and ‐5,6‐tetramethylenetetrahydro‐1,3‐oxazines

The configuration and conformation of Z‐ and E‐N‐methyl‐ and ‐N‐benzyl‐2‐p‐nitrophenyl‐4,5‐, and ‐5,6‐tetramethylenetetrahydro‐1,3‐oxazines were determined by 1H and 13C NMR spectroscopy. The Z isomers were proved to be conformationally homogeneous, having the heteroatom in axial and equatorial position, respectively, in the case of the 5,6‐ and 4,5‐tetramethylene compounds. Consequently, the p‐nitrophenyl group and the anellated cyclohexyl ring are all‐cis arranged in the Z‐5,6‐tetramethylene compounds while in the case of the Z‐4,5‐tetramethylene isomers the p‐nitrophenyl group and the cyclohexyl ring are trans arranged to the hetero ring.