OXIDATION OF 1,2-DIHYDROLEPIDINE TO LEPIDINE

Oxidation of 1,2-dihydrolepidine to lepidine using a few oxidizing agents has been studied in ethanolic solution at 65°. 1,2-Dihydrolepidine is easily autoxidized forming lepidine and hydrogen peroxide, while in the presence of HCl, it disproportionates to give lepidine and 1,2,3,4-tetrahydrolepidine. 1,2-Dihydrolepidine is oxidized by benzaldehyde, N-benzylideneaniline or methyl vinyl ketone to give lepidine and the corresponding alcohol, imine or ketone, respectively, but added HCl inhibits the oxidation in preference of the disproportionation. 1,2-Dihydrolepidine is not oxidized by 4-anilinobutan-2-one, β-ethoxyethyl methyl ketone, methyl ethyl ketone and nitrobenzene. Oxidizing agents are effective in the order: FeCl330 > 1,2-dihydrolepidine-HCl (disproportionation) > O2 > PhCHO ∼ PhCHNPh > CH3COCHCH2. © 1969.