The insecticidal lead 1,1-difluorododec-1-ene was optimised. This compound has attractive insecticidal activity against tobacco budworm (Heliothis virescens), banded cucumber beetle (Diabrotica balteata), pea aphid (Aphis cracciovora), brown planthopper (Nilaparvata
lugens), and green rice leafhopper (Nephotettix cincticeps). Among different pharmacophore analogues, only 1,1-dichlorododec-1-ene and 1,1-difluoro-2-iodododec-1-ene showed weak insecticidal activity, whereas similar compounds such as 1-chloro-1-fluorododec-1-ene, 1-fluorododec-1-ene,
and 1,1-difluoro-2-bromododec-1-ene were inactive. Only bridge analogues with even-numbered carbon chains were active, for example 1,1-difluorodec-1-ene and 1,1-difluorotetradec-1-ene. Odd-numbered analogues such as 1,1-difluoronon-1-ene, 1,1-difluoroundec-1-ene, 1,1-difluorotridec-1-ene,
and 1,1-difluoro-pentadec-1-ene showed no activity. Modification of the tail group led to the analogues 12,12-difluorododec-11-enoic acid and its methyl ester, 12,12-difluorododec-11-en-1-ol, 1,1-difluoro-12-methoxydodec-1-ene, and 12,12-difluorododec-11-enylamine, all of which showed insecticidal
activity. 12,12-difluorododec-11-enoic acid methyl ester, 12,12-difluorododec-11-enoic acid, and 12,12-difluorododec-11-en-1-ol were also active against spider mites (Tetranychus ssp). Thus, in a first optimisation cycle, broad activity against insect pests and mites was discovered.
Two requirements, the gem-difluorovinyl pharmacophore and an even-numbered carbon chain, were found to be essential for activity. This latter requirement is in line with the proposed mode of action, which involves inhibition of the ? -oxidation of fatty acids in insect mitochondria.
In a second optimisation cycle, it was found that 6,6-difluorohex-5-enoic acid and its derivatives, such as acids, amides, and hydrazides, possess even superior properties as insecticides and acaricides. This led to the discovery of 6,6-difluorohex-5-enoic acid 2-[4-(4-trifluoromethylbenzyloxy)-phenoxy]-ethyl
ester (CGA 304'111). This compound showed excellent performance in field trials against a wide range of pests, as well as a more favourable toxicological profile than earlier derivatives. For a largescale synthesis of CGA 304'111, five different synthetic routes for 6,6-difluorohex-5-enoic
acid were developed. The best route involved radical addition of CBrClF2 to pent-4-enoic acid. Removal of bromine by hydrogenation, elimination of chloride and hydrolysis of the ester concluded this most efficient sequence. Thus, a practical synthesis for CGA 304'111 was identified,
which allowed the preparation of samples on a several 100 g scale.
1,1-二氟十二烯是一种杀虫剂铅化合物,具有对烟草夜蛾、条纹黄瓜甲(Diabrotica balteata)、豌豆蚜虫(Aphis cracciovora)、褐飞虱(Nilaparvata lugens)和绿稻叶蝉(Nephotettix cincticeps)等昆虫的吸引力杀虫活性。在不同的药效团类似物中,只有1,1-二氯十二烯和1,1-二氟-2-碘十二烯表现出微弱的杀虫活性,而类似化合物如1-氯-1-氟十二烯、1-氟十二烯和1,1-二氟-2-溴十二烯则无活性。只有具有偶数碳链的桥接类似物才具有活性,例如1,1-二氟十烯和1,1-二氟十四烯。奇数碳链的类似物如1,1-二氟壬-1-烯、1,1-二氟十一-烯、1,1-二氟十三-烯和1,1-二氟十五-烯均没有活性。修改尾基导致类似物12,12-二氟十二-11-烯酸及其甲酯、12,12-二氟十二-11-烯-1-醇、1,1-二氟-12-甲氧基十二烯和12,12-二氟十二-11-烯基胺,均表现出杀虫活性。12,12-二氟十二-11-烯酸甲酯、12,12-二氟十二-11-烯酸和12,12-二氟十二-11-烯-1-醇也对蜘蛛螨(Tetranychus ssp)具有活性。因此,在第一个优化周期中,发现了对昆虫害虫和螨类广泛活性。两个要求,即gem-二氟乙烯药效团和偶数碳链,被发现是活性所必需的。后一个要求符合所提出的作用模式,涉及对昆虫线粒体中脂肪酸的β-氧化的抑制。在第二个优化周期中,发现6,6-二氟己-5-烯酸及其衍生物,如酸、酰胺和肼,具有更优越的杀虫剂和杀螨剂性能。这导致了6,6-二氟己-5-烯酸2-[4-(4-三氟甲基苄氧基)-苯氧基]-乙酯(CGA 304'111)的发现。这种化合物在田间试验中表现出对多种害虫的优异性能,且毒理学特性比早期衍生物更有利。为了大规模合成CGA 304'111,开发了六种不同的6,6-二氟己-5-烯酸合成路线。最佳路线涉及对戊-4-烯酸进行自由基加成反应。通过氢化去除溴,消除氯并水解酯结束了这个最有效的序列。因此,确定了CGA 304'111的实用合成方法,可以在数百克的规模上制备样品。