1973 Volume 21 Issue 12 Pages 2695-2704
The mercuric acetate-EDTA oxidation of 1-(3, 4-dimethoxyphenyl)-2-piperidinoethanol (IV : R1=H ; R2=CH3O) to form 1-[2-(3, 4-dimethoxyphenyl)-2-hydroxyethyl]-2-piperidone (XI : R1=H ; R2=CH3O) was extended to include 3-alkylpiperidine derivatives (IV : R1=CH3, C2H5), which were synthesized from 3-alkylpyridines (II : R1=CH3, C2H5) by quaternization with phenacyl bromides followed by catalytic and NaBH4 reductions. It was found that the 3-methyl and 3-ethyl groups of IV almost equally oriented the oxidation to both the 2- and 6-positions but with a slight advantage to the latter position. In contrast, the alkaline ferricyanide oxidation of quaternary salts V (R1=CH3, C2H5) at 32°produced 2-pyridones (IX) as the main product and 6-pyridones (XIII) as the minor product. It seemed that a higher 3-alkyl substituent caused the extent of 6-pyridone formation to increase slightly (Table I). The structures of the pyridones (IX and XIII) were assigned on the basis of their ultraviolet, infrared, and nuclear magnetic resonance spectra (Tables II and III), and the chemical correlations (IX→VI←VII and XIII→X←XI) shown in Chart 2 established the structures of the hydroxypiperidones (VII and XI) obtained by the mercuric acetate-EDTA oxidation method. In alternative synthesis of Xe, 1-benzyl-5-ethyl-2-piperidone (XV) was debenzylated with sodium and liquid ammonia to give XIV. Treatment of the potassium salt of XIV with phenethyl bromide furnished Xe.
