Production of dihydronepetalactone
View Patent ↗This invention provides a process for producing dihydronepetalactone using mixtures comprising both trans-cis nepetalactone and cis-trans nepetalactone. A reaction mixture comprising trans-cis nepetalactone and cis-trans nepetalactone is first contacted with hydrogen in the presence of at least one hydrogenation catalyst under conditions that optimise the preferential conversion of trans-cis nepetalactone to dihydronepetalactone. Cis-trans nepetalactone is subsequently converted to dihydronepetalactone by contact with hydrogen in the presence of at least one hydrogenation catalyst.
1. A process for preparing dihydronepetalactone comprising:
(a) contacting in a reaction mixture a starting amount of trans-cis nepetalactone (Formula I) and a starting amount of cis-trans nepetalactone (Formula II)
with hydrogen and a palladium on carbon catalyst at a first temperature or temperatures until the amount by weight of trans-cis nepetalactone in the reaction mixture is no more than about 50% of the starting amount thereof, to form a first product mixture; and
(b) contacting the first product mixture with hydrogen and a palladium on carbon catalyst, at a second temperature or temperatures to form a dihydronepetalactone reaction product;
wherein step (a) is performed at a temperature or temperatures in the range of from about 0° C. to 100° C., and step (b) is performed at a temperature or temperatures in the range of from 50° C. to 150° C.; and
wherein the temperature or temperatures in step (b) are higher than the temperature or temperatures in step (a).
2. The process of claim 1 wherein step (a) is performed at a temperature or temperatures in the range of from about 0° C. to about 60° C., and step (b) is performed at a temperature or temperatures in the range of from greater than 60° C. to about 150° C.
3. The process of claim 1 wherein step (a) is performed at a temperature or temperatures in the range of from about 0° C to about 50° C, and step (b) is performed at a temperature or temperatures in the range of from greater than 60° C. to about 150° C.
4. The process of claim 1 wherein the amount by weight of trans-cis nepetalactone in the reaction mixture is no more than about 10% of the starting amount thereof.
5. The process of claim 1 wherein the hydrogen feed pressure is in the range of from about 0.1 MPa to about 20.7 MPa.
6. The process of claim 1 wherein, in the starting mixture, the ratio of the content by weight of cis-trans nepetalactone to the content by weight of trans-cis nepetalactone is at least about 2/1.
7. The process of claim 1 wherein the reaction product contains less than about 10 wt % puleganic acid.