Study On Synthesis And Herbicidal Activity Of P-Menthadiene Derviatives

p-Menthadiene derivatives such as limonene,perillyl alcohol and perillaldehyde exist widely in nature,which are generally ultilized as monoterpenoid perfumes,as well as intermediates of medicine and pesticide.However,p-menthadiene derivatives have not been studied and ultilized plentifully yet,there is absence of high value-added green products.The aim of this study is to synthesize a series of new p-menthadiene derivatives which possess herbicidal activities,as a foundation for developing novel green pesticide.Using p-menthadiene and acetonitrile as raw materials,1,8-p-menthane diacetamide was prepared under the catalysis of sulfuric acid solution.The effects of the mass fraction of sulfuric acid solution,the molar ratio of p-menthadienes to sulfuric acid solution and acetonitrile,the reaction temperature,the reaction time and the type of p-menthadienes on the yield of 1,8-p-menthane diacetamide were optimized.The results showed that the yield of1,8-p-menthane diacetamide is higher under conditions as c_{sulfuric acid}=60%,n_{sulfuric acid}?n_{p-menthadiene}=2.2?1,n_acetonitrile?n_{p-menthadiene}=2.4?1,T=55 C,t=6 h.For example,1,8-p-menthane diacetamide has been obtained in the yiled of 61.6%,when limonene was used as the starting material.cis-1,8-p-menthanediamine was obtained from 1,8-p-menthane diacetamide by alkali hydrolysis combined with vacuum distillation.And a series of cis-1,8-p-menthane-di-sec-amines?A1?A17?were synthesized by aldehyde amine condensation and reduction reactions from cis-1,8-p-menthanediamine in yields of 81%?98%.Then,8 perillyl-sec-amines?B1?B8?were synthesized by the aldehyde condensation and reduction reaction from perillaldehyde in yields of 56%?70%.Thereafter,10 perillyl esters?C1?C10?were synthesized by esterification reaction from perillyl alcohol in yields of 54%?89%.The structures of above35 compounds were identified by FT-IR,ESI⁺-MS,GC-MS,¹H NMR and ¹³C NMR.The herbicidal activity of above 35 p-menthadiene derivatives against barnyardgrass?Echinochloa crusgalli?were evaluated by the herbicide dish method,and the relationships between the molecular structure and the herbicidal activity were also studied.The results indicated that,the perillyl esters have poor herbicidal activities,but the most of cis-1,8-p-menthane-di-sec-amines and some of perillyl-sec-amines have strong herbicidal activities.Among all the 35 compounds,n-hexyl perillyl amine?B8?acted the best herbicidal activity which is far higher than that of the commercially available herbicide atrazine.The IC₅₀values of B8 on the stem growth and root growth of barnyardgrass were 0.12 mmol/L and0.036 mmol/L,respectively,which were lower than those?0.86 mmol/L and 1.02 mmol/L,respectively?of the positive control atrazine.The structure-activity relationship indicated that the introduction of benzene ring into cis-1,8-p-menthane-di-sec-amines improved the herbicidal activity,and the introduction of alkyl group into perillyl-sec-amines significantly improved the herbicidal activity.The safety of the selected p-menthadiene derivatives with excellent herbicidal activity were evaluated by the MTT method and the results showed that the new active p-menthadiene derivatives are safe to human body.