The method is for preparing an isomer of an a-cyano-3-phenoxybenzyl-2-(4-chlorphenyl)isovalerate or of the derivative having 4-fluoro on the phenoxy nucleus; these compounds have two asymmetric carbon atoms.
The starting material is a solution which consists of or is rich in a racemic mixture of the isomers of the compound having respectively an (S) configuration on the acid moieties and respectively an (S) or (R) configuration on the alcohol moiety; in the presence of seed crystal of substantially pure (S)-(S) isomer, the (SHS) isomer is crystallized from the solution. The solution may be heated to at least 40 °C. The seed crystal can be one obtained by recrystallization. The solvent is preferably an alcohol, aliphatic hydrocarbon and/or alicyclic hydrocarbon. A basic catalyst, e.g. ammonia or triethylamine, can be present. Preferably the solution is at a temperature and concentration so as to be supersaturated in racemic mixture.
The product isomer has high insecticidal and/or acaricidal efficacy.
该方法用于制备 a-
氰基-3-苯氧基苄基-2-(4-
氯苯基)
异戊酸酯的异构体或在苯氧基核上具有 4-
氟的衍
生物;这些化合物具有两个不对称碳原子。
起始原料是一种溶液,其中包含或富含化合物异构体的外消旋混合物,这些异构体的酸基分别具有(S)构型,醇基分别具有(S)或(R)构型;在存在基本纯的(S)-(S)异构体的种子晶体的情况下,(SHS)异构体从溶液中结晶出来。溶液可加热至至少 40 °C。籽晶可以是通过重结晶得到的。溶剂最好是醇、脂肪烃和/或脂
环烃。可以加入碱性催化剂,如
氨或
三乙胺。溶液的温度和浓度最好能使外消旋混合物达到过饱和。
产品异构体具有很高的杀虫和/或杀螨效 果。