Studies On The Catalytic Synthesis And Selective Oxidation Of Myrtenol

Myrtenal is a useful fragrance and widely used in many aspects. Moreover, as an important organic intermediate, myrtenal can be used to produce a series of more valuable fragrances and sweeteners such as perillartine. In this work, myrtenal was synthesized by the selective oxidation of myrtenol obtained by the rearrangement of 2,10-epoxypinane. This method has advantages of moderate reaction condition, easily obtained the raw material and afforded the good yield. Therefore, the rearrangement reaction of 2,10-epoxypinane and selective oxidation of myrtenol are investigated in this dissertation and the main significant results are obtained as follows:1. The isomerization of 2,10-epoxypinane and the product distributions have been studied in the past years. It was discovered that liquid phase isomerization of 2,10-epoxypinane mainly produced perilla alcohol catalyzed by ammonium nitrate in strongly polar protonic solvent MeNO₂. On the basis of these works, effects of reaction conditions on isomerization are investigated in weak polar or non-polar solvents, it is discovered that the isomerization of 2,10-epoxypinane produced mainly myrtenol catalyzed by NH₄NO₃. Myrtenol can be obtained with 65.69 % of yield and 84.07 % of conversion in CHCl₂CH₂Cl under the optimized conditions.2. The influences of the different anions in the ammonium salt catalysts on the isomerization reaction were investigated in this work. The experimented results indicate that NH₄Cl and CH₃COONH₄ have relatively good activity and high selectivity to myrtenol. The conversion of 2,10-epoxypinane could be reached up to 82.94 % and 65.13 % of selectivity to myrtenol after 16 h when NH₄Cl was used as catalyst.3. Selective oxidation of myrtenol to myrtenal was studied in the presence of active MnO₂, the supported CrO₃/SiO₂, CrO₃/γ-Al₂O₃(a) and CrO₃/γ-Al₂O₃(b). The results show that the myrtenal can be obtained with the conversion of 86.80 % and the yield of 77.07 % via oxidation of perrllyl alcohol by activated MnO₂ in the ethyl acetate under solvent reflux temperature for 24 h and the mass ratio of oxidant to myrtenol is 4:1. Moreover, the supported oxidants CrO₃/SiO₂, CrO₃/γ-Al₂O₃(a) and CrO₃/γ-Al₂O₃(b) were prepared by dry mixing method and the reaction regulations of synthesizing myrtenal through supported oxidants selectively oxidizing myrtenol were studied. The effects of the amount of supported oxidant, solvent and reaction conditions on yield of myrtenal are examined. It was found that the polar solvent was favorable for the oxidation of myrtenol. The results show that activity order of supported oxidants is SiO₂ >γ-Al₂O₃(b)>γ-Al₂O₃(a), and the conversion of myrtenol reached up to 94.33 % with 82.06 % of yield to myrtenal in dichloromethane, the ratio of 2.5:1 for oxidant to myrtenol and the loading amount of CrO₃/SiO₂(2mmol/g) at room temperature for 8h.