Process for increasing the cis content of a mixture of cis and trans isomers of S-isopropyl-1-(5-ethyl-2-methylpiperidinecarbothioate)

摘要

A mixture of cis and trans isomers of S-isopropyl-1-(5-ethyl-2- methylpiperidinecarbothioate) has been found to have improved herbicidal properties in contrast to the trans isomer alone. Preferably the mixture contains at least about 20%, most preferably between about 60 and about 65%, of the cis isomer.PPThe S-isopropyl-1-(5-ethyl-2- methylpiperidinecarbothioate) having a desired amount of cis isomer can be produced by a two-step process comprising hydrogenation of 2-methyl-5- ethyl pyridine using a catalyst comprising rhodium supported on activated carbon to produce 2-methyl-5-ethyl piperidine and reacting the piperidine with isopropyl chlorothiolformate.