Synthesis And Characterization Of High-quality Synthetic Borneol And Key Intermediates

Borneol,generally exists in Dipterocarpaceae plants,Dipterocarp tree and some fresh branches,leaves,trunks of Lauraceae?D-borneol?or Asteraceae Blumea leaves?L-borneol?.Isoborneol and borneol are epimers.Natural borneol cannot satisfy the increasing demand of mankind,and how to generate synthetic borneol efficiently becomes a hot spot that people in natural product chemistry field pursue.In current days,borneol is mainly synthesized from pinene esterification-saponification.Rich turpentine resources in China can bring great convenience to synthetic borneol,for pinene is the main component of turpentine.However,as to the synthetic borneol catalyzed by boron anhydride-acetic anhydride and metatitanic acid catalyst,there exists such a phenomenon as low yield rate and poor quality.Therefore,how to solve these problems and reduce the side effects of isoborneol become a major concern for relevant enterprises and institutes.In this study,high-quality synthetic borneol was obtained by controlling process conditions,and the auther gradually explored the reasons.The major content was as below:The auther found that high-quality synthetic borneol could be generated by controlling process conditions.The results showed that the optimal synthetic conditions of this reaction were:200.0 g?-pinene,c₃ g boron anhydride,2.0 mL acetic anhydride,m₁ g anhydrous oxalic acid?firstly?and m₂ g?t min later?,reaction temperature 55??t₁'min before?and 52??later?and reaction time t₂ min.Then we distilled the filtrated-washed reaction oxalic ester to remove monoterpenoid oil.After saponification,steam distillation method was used to bring synthetic borneol out.Under the reaction conditions,the yield rate of monoterpenoid oil and synthetic borneol were 50.7%and 26.6%,respectively.Borneol proportion in GC normalization of borneol and isoborneol was 77.8%,higher than current industrial products.Borneol and isoborneol was isolated by column chromatography separation technology,and the structure of borneol and isoborneol were identified and characterized by IR,GC-MS,¹H NMR and ¹³C NMR.Then,considering the reasons of getting high-quality synthetic borneol through controlling process conditions,gas chromatography?GC?was used to analyze the changs in this paper.The author explored the peak separation of components under different programmed temperature,and initially built GC method of tracking reaction trends.Diisobornyl oxalate was synthesized from rearrangement-addition?esterification?reaction between oxalic acid and camphene?isoborneol?catalyzed by boric anhydride.We finally selected camphene as raw material by comparing them.The results showed that the optimal synthetic conditions of this reaction may be as follows:13.6 g camphene,8.0 g catalyst,16.0 g anhydrous oxalic acid,reaction time 96 h and reaction temperature 55?.Under the reaction conditions,the conversion rate of camphene and the selectivity of diisobornyl oxalate were89.5%and 95.6%,respectively.The structure of diisobornyl oxalate was identified and characterized by IR,HPLC-ESI-MS,LCMS-IT-TOF,¹H NMR and ¹³C NMR.Dibornyl oxalate was synthesized from esterification reaction between oxalic acid and borneol catalyzed by boric anhydride or metatitanic acid.We finally selected metatitanic acid as catalyst because of its fast reaction speed,high conversion rate and few side effects.The results showed that the optimal synthetic conditions of this reaction were:5.0 g borneol,3.0 g catalyst,12.0 g anhydrous oxalic acid,reaction time 96 h and reaction temperature 55?.Under the reaction conditions,the conversion rate of borneol and the selectivity of dibornyl oxalate were 95.8%and 99.4%,respectively.The structure of dibornyl oxalate was identified and characterized by IR,HPLC-ESI-MS,¹H NMR and ¹³C NMR.Comparing with diisobornyl oxalate and dibornyl oxalate,GC was used to analyze the changs in this paper to explored the reasons why we can obtain high-quality synthetic borneol,and the mechanism was discussed.