Acetylene derivatives

Summary

• 1. Reduction of 2,5-dimethyl-1-phenyl-4-piperidone (I) by sodium in moist ether, by sodium in alcohol, or by hydrogenation in presence of a platinum or nickel catalysts yields two stereoisomeric 2,5-dimethyl-1-phenyl-4-piperidols (II).

• 2. Hydrogenation of the hydrochloride of 2,5-dimethyl-1-phenyl-4-piperidone in presence of a platinum catalyst gives only one stereoisomeric form, which corresponds to the low-melting form of the base (II, α-form).

• 3. A number of tertiary 4-piperidinols have been prepared by the action alkylmagnesium halides and of phenyllithium on 2,5-dimethyl-1-phenyl-4-piperidone (VII). It has been established that in each case only one stereoisomeric form of the tertiary 4-piperidinol was formed.

• 4. By means of the condensation of 2,5-dimethyl-1-phenyl-4-piperidone with acetylene in presence of powdered caustic potash, the preparation has been effected in 50% yield of 4-ethynyl-2,5-dimethyl-1-phenyl-4-piperidinol (III) which was converted, by exhaustive hydrogenation, in the second stereoisomer of 4-ethyl-2,5-dimethyl-1-phenyl-4-piperidinol (IV).

• 5. The syntheses have been carried out of esters of both isomeric forms of 2,5-dimethyl-1-phenyl-4-piperidinol with acetic, propionic, benzoic, p-nitrobenzoic, and p-aminobenzoic acids.

• 6. By means of various methods of esterification, the esters formed by 4-ethyl-2,5-dimethyl-1-phenyl-4piperidinol and by 2,5-dimethyl-1,4-diphenyl-4-piperidinol with acetic, propionic and benzoic acids have been prepared.