Synthesis of 2,5-dimethyl- and 1,2,5-trimethyl-4-dimethoxyphosphinylpiperid-4-ols

Dimethyl phosphite is condensed with 2,5-dimethyl- and 1,2,5-trimethylpiperid-4-ones in the presence of alkali metal alkoxides. It is shown that 2,5-dimethyl- and 1,2,5-trimethyl-4-dimethoxyphosphinyl-piperid-4-ols are formed in both cases in the same stereoisomeric forms and in high yields. Methylation of the piperidol isomer which was not substituted at the nitrogen atom indicated that the two piperidols formed had the same configuration.