Birch reduction of (-)-ephedrine. Formation of a new, versatile intermediate for organic synthesis

The reduction of (-)-ephedrine by lithium in liquid ammonia resulted in the formation of S-1-(1,4-cyclohexadien-1-yl)-N-methyl-2-propanamine. In addition to the reduction of the aromatic ring, the hydroxy group was reduced as well. The resulting 1,4-cyclohexadienyl group is a potentially versatile intermediate for further synthetic transformations. The ozonolysis of this group was investigated, producing derivatives of β-keto-δ-methylamino esters and β-keto aldehydes which could be subsequently converted to heterocycles. The restriction to rotation of the C-N bond in N-benzoyl-1-(1,4-cyclohexadien- 1-yl)-N-methyl-2-propanamine is described.