The N-methylpyridinium salt of 6,7,dihydro-6-methyl-5-oxopyridino[3,2-d]-2-benzazepin has been synthesized. The salt has axial chirality with respect to the orientation of the carbonyl dipole. An enantiomer of the cation has been obtained as the iodide salt. Reduction of the salt results in the corresponding dihydropyridine derivative stereospecifically. The stereochemistry of the reduction is controlled entirely by the electronic effect of the carbonyl dipole.