Latest generation of halogen‐containing pesticides

Agriculture is confronted with enormous challenges, from production of enough high‐quality food to water use, environmental impacts and issues combined with a continually growing world population. Modern agricultural chemistry has to support farmers by providing innovative agrichemicals, used in applied agriculture. In this context, the introduction of halogen atoms into an active ingredient is still an important tool to modulate the properties of new crop protection compounds. Since 2010, around 96% of the launched products (herbicides, fungicides, insecticides/acaricides and nematicides) contain halogen atoms. The launched nematicides contain the largest number of halogen atoms, followed by insecticides/acaricides, herbicides and fungicides. In this context, fungicides and herbicides contain in most cases fluorine atoms, whereas nematicides and insecticides contain in most cases ‘mixed’ halogen atoms, for example chlorine and fluorine. This review gives an overview of the latest generation of halogen‐containing pesticides launched over the past 6 years and describes current halogen‐containing development candidates. © 2017 Society of Chemical Industry     

The unique role of halogen substituents in the design of modern agrochemicals

The past 30 years have witnessed a period of significant expansion in the use of halogenated compounds in the field of agrochemical research and development. The introduction of halogens into active ingredients has become an important concept in the quest for a modern agrochemical with optimal efficacy, environmental safety, user friendliness and economic viability. Outstanding progress has been made, especially in synthetic methods for particular halogen‐substituted key intermediates that were previously prohibitively expensive. Interestingly, there has been a rise in the number of commercial products containing ‘mixed’ halogens, e.g. one or more fluorine, chlorine, bromine or iodine atoms in addition to one or more further halogen atoms. Extrapolation of the current trend indicates that a definite growth is to be expected in fluorine‐substituted agrochemicals throughout the twenty‐first century. A number of these recently developed agrochemical candidates containing halogen substituents represent novel classes of chemical compounds with new modes of action. However, the complex structure–activity relationships associated with biologically active molecules mean that the introduction of halogens can lead to either an increase or a decrease in the efficacy of a compound, depending on its changed mode of action, physicochemical properties, target interaction or metabolic susceptibility and transformation. In spite of modern design concepts, it is still difficult to predict the sites in a molecule at which halogen substitution will result in optimal desired effects. This review describes comprehensively the successful utilisation of halogens and their unique role in the design of modern agrochemicals, exemplified by various commercial products from Bayer CropScience coming from different agrochemical areas. Copyright © 2009 Society of Chemical Industry     

A New Group of Plant-Derived Naphthoquinone Pesticides

A series of compounds with structures based on insecticidal/acaricidal naphthoquinones isolated from Calceolaria andina has been synthesised. A feature of the series is the lack of resistance shown by strains resistant to established classes of pesticides. The importance for activity of the tetra-substituted carbon atom in the side-chain, as observed in the natural products, has been investigated. In analogues with acyclic side-chains the position of the tetra-substituted carbon for optimum activity was dependent on the length of the side-chain. With cyclic side-chains, activity was dependent on the size of the ring, the number and position of the substituents therein. Activity of the compounds examined was particularly high against Bemisia tabaci and Tetranychus urticae in direct-contact tests, but was much lower than expected in leaf-dip tests. A partial improvement based on formulation has been demonstrated. © 1997 SCI     

新型高效杀虫剂茚虫威毒理学研究进展

新型噁二嗪类杀虫剂茚虫威对鳞翅目昆虫具有卓越的杀虫活性。神经毒理学研究表明,茚虫威在昆虫体内活化为N 去甲氧羰基代谢物（DCJW）,并作用于失活态钠离子通道,破坏神经冲动传递。近年来对茚虫威的研究表明,昆虫具有对茚虫威产生高水平抗性的风险。     

杀虫剂的作用方式与分类

随着杀虫剂产品的逐渐增多,按照其作用方式进行分类显得十分重要,不仅有利于新化合物的合成与筛选,而且有助于了解其抗药性以及科学地使用。本文收集了杀虫剂(杀螨剂)共253种,分属19种不同的作用方式和60种不同的化合物类别。     

棉蚜对新烟碱类杀虫剂的抗性现状及其治理策略

棉蚜Aphis gossypii Glover是棉花生产中最严重的害虫之一。长期以来防治棉蚜主要依赖于化学杀虫剂,其中新烟碱类杀虫剂扮演着十分重要的角色,但由于其长期、大量的使用,棉蚜已对该类杀虫剂产生了较高水平的抗性,严重影响了对棉蚜的防治效果。抗性机制研究表明,棉蚜对新烟碱类杀虫剂产生抗性的机制主要涉及解毒代谢能力增强和靶标敏感性下降。细胞色素P450、羧酸酯酶、谷胱甘肽S-转移酶、UDP-葡糖基转移酶等解毒酶基因过量表达介导的解毒代谢增强和烟碱型乙酰胆碱受体β1亚基突变引起的靶标敏感性下降是棉蚜对新烟碱类杀虫剂产生抗性的关键。针对我国棉蚜对新烟碱类杀虫剂抗性问题突出的现状,为更好地利用该类药剂防治棉蚜,亟需根据棉蚜抗性机制制定合理的抗性治理策略。本文将从棉蚜对新烟碱类杀虫剂的抗性现状、抗性机制以及抗性治理策略等方面进行综述,以期为抗性棉蚜的科学治理提供参考。     

Synthesis and insecticidal activity of nitroguanidine derivatives

Nitroguanidine derivatives with thiazol-5-ylmethyl moieties were prepared and their insecticidal activities against homopterous pests were tested. New synthetic routes for 2-chloro-5-chloromethylthiazole from 2,3-dichloro-1-propene and for substituted nitroguanidines from S-methyl-N-nitroisothiourea were established. Biological evaluation led to a novel insecticide (E)-1-(2-chlorothiazol-5-ylmethyl)-3-methyl-2-nitroguani dine (TI-435) which has a broad activity spectrum and is under development. ©1999 Society of Chemical Industry     

Dimethoxypyrimidines as novel herbicides. Part 4. Quantitative structure–activity relationships of dimethoxypyrimidinyl(thio)salicylic acids

The activity of a number of O-(4,6-dimethoxypyrimidin-2-yl)salicylic acids and their thio analogs inhibiting acetolactate synthase (ALS) preparation was measured. The effects of substituents on the salicylic-benzene ring on the inhibitory activity were analyzed quantitatively with physicochemical substituent parameters. For 6-substituted (thio)salicylic acids, the activity was shown to vary parabolically with the ‘intramolecular’ steric parameter ( E_s ). In addition, the higher steric dimension of substituents in terms of the STERIMOL width or length parameter lowered the activity. The field-inductive electron-withdrawing property of the 6-substituents in terms of the Swain–Lupton–Hansch F was favorable for the activity of salicylic acid series. In 5-substituted salicylic acids, the activity was increased by electron-donating substituents with smaller size. The relationships between ALS inhibitory and herbicidal activities were also analyzed with some weed species. Both pre- and post-emergence activities against barnyard grass, Echinochloa crus-galli, were linearly related to the ALS inhibitory activity after allowing for the hydrophobic factor that may contribute to the transport processes. Those against two broad-leaved weed species, Polygonum convolvulus and Abutilon theophrasti were linearly related to the in-vitro activity with no significant participation of the hydrophobic factor. © 1998 SCI     

防治蚜虫、白粉虱的新颖杀虫剂-吡蚜酮(pymetrozine)

嗪酮类杀虫剂可分为二嗪酮类和三嗪酮类杀虫剂,因其具有高效、低毒、作用机制独特等特点而在农药研究领域具有重要的地位,其中吡蚜酮是此类杀虫剂中的典型代表。本文综述了吡蚜酮的开发历程和作用机制,以及二嗪酮类和三嗪酮类杀虫剂的研究进展,对该类杀虫剂的构效关系进行了总结,对其发展前景进行了展望。     

Synthesis and structure–activity relationships for anticipated molluscicidal activity of some 2-amino-5-substituted pyridine derivatives

A series of 2-amino-5-substituted pyridine derivatives was synthesized and their molluscicidal activity against white garden, Theba pisana (Müller), and brown garden, Helix aspersa (Müller), snails was investigated by two methods of application. Some of these compounds showed strong activity under laboratory conditions against the two types of snail. T pisana was more sensitive to the tested compounds than H aspersa. The most effective compounds were 2-amino-5-(benzotriazole-1-ylmethyl)-3-methylpyridine, 2-amino-5-[1-(benzotriazole-1-yl)nonyl]-3-methylpyridine and 2-[(1,2,4-triazole-1-ylmethyl)amino]-3-methylpyridine which exhibited high molluscicidal activity. The toxicity results are discussed in relation to the chemical structures. © 1999 Society of Chemical Industry     

Bis-pyrimidylpyrazolinones – a new class of acetohydroxy-acid synthase (AHAS) inhibitor

Hydroxypyrazolinones which bear two pyrimidine rings (on N-1 and C-4) were found to be potent inhibitors of acetohydroxy-acid synthase which displayed good herbicidal activity in vivo. Structure–activity relationship studies suggested the presence of a second binding niche on the enzyme for a 4,6-dimethoxypyrimidine ring.     

A novel genomic approach to herbicide and herbicide mode of action discovery

A herbicide with a new mode of action has not been commercialized for more than 30 years. A recent paper describes a novel genomic approach to herbicide and herbicide mode of action discovery. Analysis of a microbial gene cluster revealed that it encodes genes for both the biosynthetic pathway for production of the sesquiterpene aspterric acid and an aspterric acid‐resistant form of dihydroxy acid dehydratase (DHAD), its target enzyme. Aspterric acid is weak compared with commercial synthetic herbicides, and whether DHAD is a good herbicide target is unclear from this study. Nevertheless, this genomic approach provides a novel strategy for the discovery of herbicides with new modes action. © 2018 Society of Chemical Industry