1.80 1.75 oc2h6 1.82 1.76 OCH(CH3)2 1.88 1.82 ch3 2.23 0.96 2.11 0.82 " 10% toluene solutions except for the 3-methyl compound which was 50% in chloroform. Chemical shifts given in (parts per million) from tetramethylsilane.A 30% solution shows the peaks shifted to 1.84 and 1.88 with incomplete resolution. The results were similar in benzene and for the other alkoxy substituents. In the case of the 3-methyl analog, the peaks were at 2.11 and 2.23 in CHC13 for the trans and cis isomers. When toluene is the solvent, care must be taken to avoid interference from the spinning side bands of the solvent methyl group.

A facile thermal equilibration of cis-(3-methoxy-2-piperidyl)-Z-propanone and some analogous cis-(&substituted 2-piperidyI)-Z-propanones with their trans isomers is reported. The effects on the equilibrium of temperature, solvent, pH, and the size of the 3 substituent were investigated. Chemical and nmr spectral data and conformational free-energy calculations are presented to support the assignment of the trans configuration to the more stable isomer.The title compounds are intermediates in the synthesis of febrifugines.A revised synthesis of the title compounds is reported.

Aus den (substituierten) o‐Picolyllithium‐Verbindungen (I) entstehen mit Acetonitril die Ketone (II), die über Rh/Aluminiumoxid zu den Piperidinen (III) (IV) hydriert werden.