Study On Synthesis Of Methyl Dihydrojasmonate

Methyl dihydrojasmonate is synthetic ketone belong to the type of jasmine,which could be synthesized in total yield of 50.9%by a key intermediate 2-pentylidene cyclopentanone from a condensation of cyclopentanone and n-valeraldehyde,followed by isomerization, Michael addition and a selective decarboxylation.The characteristics of the condensation between cyclopentanone and n-valeraldehyde in different catalytic systems were studied.The 2-pentylidene cyclopentanone,a condensation intermediate,was obtained in a yield of 88.2%by usingγ-Al₂O₃ as catalyst and m-xylene as solvent at 140℃and reaction time of 5h.With 2-pentylidene cyclopentanone as a precursor,2-pentyl cyclopentenone was synthesized in 83.6%yield.It was also found that the compound could be directly formed in one pot by employing cyclopentanone and n-valeraldehyde as raw materials in the presence of catalyst.Followed by Michael addition,83.5%yield of 3(3-oxo-2-pentyl)cyclopentyl dimethyl malonate was obtained,using sodium alcoholate catalyst at -5℃.26.1%wt of methyl alcohol to 2-Pentyl cyclopentenone,2.4%wt of natrium to 2-Pentyl cyclopentenone,reaction time of 1h.Similarly,a trimethylamino phosphorus catalyst was applied to the solvent-free Michael addition.Finally,methyl dihydrojasmonate was synthesized through the hydrolyzation and selective decarboxylation of 3(3-oxo-2-pentyl) cyclopentyl dimethyl malonate,up to a yield of 82.6%.