Synthesis And Acaricidal Activity Of (E)-1-arylhept-2-ene-1-one Compounds

Itch mite is a kind of skin parasites on rabbit,horses,cattle,sheep and so on.It cancause animal skin itching,hair removal,emaciation and even death,and bring great economic losses to the breeding industry.Chemical acaricides（such as ivermectin）are toxic and environmentally unfavorable,long-term use makes the mites produce resistance,and will cause serious environmental pollution.There are naturally occurring natural products containing 1-aryl-α,β-unsaturated ketone structures,a large number of studies have shown that these compounds have antibacterial,anti-tumor,anti parasitic,antioxidant and other biological activities,but these compounds have not been systematically reported for the activity of the itch mite.In this paper,a series of compounds containing 1-aryl-α,β-unsaturated ketone structure were designed and synthesized based on the existing synthetic methods.The killing activity of these compounds against rabbit itch mites was studied,and their structure-activity relationship was analyzed.The main achievements of this paper are as follows:1.21（E）-1-arylhept-2-ene-1-one compounds and one reduction product were synthesized by the basic method of aldol condensation catalyzed by water as the basic catalyst.All compounds were confirmed by ¹H NMR,¹³C NMR,¹⁹F NMR,MS,and nine of these compounds were not reported.2.The acaricidal activity of all the compounds against rabbit itch mites was determined by immersion method.The results showed that these compounds generally had certain acaricidal activity,and nine of them（2,3,5,7,12,13,14,15,16）showed better acaricidal activity.When the test concentration was 200μg/m L,the mortality rate of mites was between 86%and 100%,which was higher than that of the clinical first-line acaricide standard-ivermectin（51%）.The nine compounds were evaluated for virulence,the results showed that the LC₅₀ of the nine compounds was lower than that of ivermectin（247.40μg/m L）the LC₅₀ of compounds 2,3,7 and 16 was less than 50μg/m L,LC₅₀ of compound 5 was close to 50μg/m L.At 2.0 mmol/L,the half-lethal time LT₅₀ of compounds 3,5,7,and 16 was less than ivermectin（139.58 min）,and LT₅₀ of compound 14 was close to ivermectin.Wherein the LT50 of compound 3 is 18.2 min and compound 7 and compound 16 are 67.4 min respectively.3.The structure-activity relationship of the acaricidal activity of（E）-1-arylhept-2-ene-1-one compounds was discussed.In general,different substituents on the benzene ring and the different positions of the same substituents affect the acaricidal activity of the compound.In general,the introduction of the substituents will reduce the activity of the compounds to varying degrees.The activity of the nitro,methyl and fluoro substituted compounds is better than that of the other substituents.The activity of the para-substituted compounds is generally more pronounced than the ortho and meta.The reduction of carbonyl has little effect on the activity of the compound,and theβ-OH ketone structure greatly reduces the activity of the compound.In view of the above,（E）-1-arylhept-2-ene-1-one compounds generally have good acaricidal activity,particularly compounds 3,7 and 16 show better acaricidal activity,which expected to be used to develop new types of acaricides.