Research On The Synthesis Of Methyl Dihydrojasmonate

Methyl dihydrojasmonate (MDHJ) is an important fragrance compound with remarkable olfactory properties. It is a desirable constituent of famous fragrances and a key ingredient universally employed in the manufacture of high-grade perfume compositions. Numerous syntheses of MDHJ have been reported in the literature since1960. Developing facile, safe, convenient and efficient synthetic methods for MDHJ is still a concern for many chemists confronted with synthetic problems.In this dissertation, MDHJ was synthesized via acondensation of cyclopentanone and n-valeraldehyde, followed by isomerization, Michael addition and a selective decarboxylation and all the process was optimized. The results provided theoretical and practical experiences for the industrialized production of MDHJ. The concrete operating procedures were shown as follows.Firstly,2-pentylidene-cyclopentanone was prepared starting from valeraldehyde and cyclopentanone via a selective aldol condensation recation. It was found that82.75%yield of2-pentylidene-cyclopentanone was achieved under the condition as follows:n(valeraldehyde):n(cyclopentanone)=1:1.3, under80℃and the reaction time was1h.Subsequently, the prepared2-pentylidene-cyclopentanone, was isomerizated into2-pentyl-cyclopentanone in the presence of acid catalyst. The optimum result was obtained by orthogonal and single-factor experiments, that was n(p-toluenesulfonic acid):n(acetic anhydride): n(xylene): n(2-pentylidene-cyclopentanone)=0.004:0.37:0.44:1, the reaction yield reached86.01%under125℃.Finally,2-pentyl-cyclopentanone was transformed to MDHJ, by Michael addition and selective decarboxylation. It was found that82.51%yield of MDHJ was achieved under the condition as follows, Michael addition: n(sodium methoxide): n(methnol):n(dimethylmalonate):n(2-pentyl-cyclopentanone)=1:1.69:3.27:2.84under10℃and the reaction time was1h, selective decarboxylation: n(H2O) n(2-pentyl-cyclopentanone)=5.74:1, under200℃and the reaction time was1. h, total yield of the two reaction was82.51%Methyl dihydrojasmonate could be prepared in58.71%yield with a purity of97.04%proved by GC under optimized conditions, and the structure of all intermediates and final product was confirmed by1H-NMR,13C-NMR...