Study On The Synthesis And Biological Activity Of Nitroguanidine Derivatives

Due to the increasingly resistance of pesticides,the development of new,efficient and low-toxic pesticides has great significance for the subsequent agricultural development.In this paper,a series of novel sulfoximine compounds were designed and synthesized by oxidative coupling reaction of nitroguanidine and thioether through the method of active substructure connection.It is expected that the compounds with excellent bactericidal active will be obtained.Using nitroguanidine as a raw material,thirty target compounds were synthesized by substitution reaction and two-step oxidation reaction.The conditions of the substitution reaction and the first-step oxidative coupling reaction were optimized.The factors affecting the reaction such as base,solvent,oxidant and reaction time were discussed too.The suitable conditions for the substitution of nitroguanidine were determined that the reactions were carried out for 12 h in the presence of Na H.The ratio of imidation with regard to sulfide,N-alkyl-nitroguanidines and oxidant was 1.5:1:1.5 and the corresponding products were prepared in DMF in highest yield.The synthesized target compounds were characterized by ¹H NMR,¹³C NMR and HRMS.At the concentration of the target compound of 500 mg/L,taking the second-instar mid-aged aphid as the test object,the insecticidal activity of the aphid by dipping method showed that the compound had no insecticidal activity.At a concentration of 500 mg/L of the target compound,five pathogens are the test object,the antibacterial activity of the target compound against five pathogenic bacteria is tested by the mycelial growth rate method,and the results show that the the antibacterial activity of the compounds SQ-03,SQ-05,SQ-06,SQ-13,SQ-26,SQ-27 against Fusarium graminearum are 66.5%,52.3%,51.8%,66.6%,67.3%and 64.5%.Further investigation revealed that the activity of SQ-05,SQ-11,SQ-14,SQ-16,SQ-27 against Phytophthora capsici are56.3%,56.8%,66.3%,51.3%and 59.3%respectively.The study on the activity of SQ-05,SQ-11,SQ-14,and SQ-27 against Botrytis cinerea exhibited 58.9%,51.9%,63.2%and74.5%.Among them,compounds SQ-05 and SQ-27 had stronger antibacterial activity against several pathogenic bacteria.The EC₅₀of some compounds with good bacteriostatic activity were tested.Based on the results of the initial screening,a preliminary structure-activity relationship study was conducted.When R₁is an arylmethyl group with electron-withdrawing and R₂is an alkyl group or an arylmethyl group with electron-withdrawing,the target compound has better antibacterial activity.The preliminary structure-activity relationship research results can lay the foundation for subsequent molecular optimization and design.