The invention relates to a process for preparing immediate precursors for pyroxasulfone and fenoxasulfone preparation of the formula (I). The process comprises a bromination reaction of a benzylic position without light irradiation (step a), followed by thoination reaction, which substitutes the bromine atom (step b) and after the protecting group is removed, and the revealed thiol or thiolate reacts with a substituted isoxazoline bearing a leaving group at the 3-position (step c), wherein Y = protecting group. In another variant of the invention the pyroxasulfone or fenoxasulfone immediate precursor is synthesized from the arylmethyl bromide by first forming a carbon-sulfur bond at the 3-position of a 2-isoxazoline through displacement of a leaving group at the 3-position (particularly acid derived residues such as phosphoryl, sulfanyl, halo, cyano or carboxyl groups) by an appropriate thionating reagent. The resulting adducts, which is a S-protected 3-thio-2-isoxazoline, may be treated with base to remove the protecting group, to reveal a thiol or thiolate which may subsequently react with the arylmethyl bromide to form the Pyroxasulfone or Fenoxasulfone immediate precursor. Ar = aryl, Y = protecting group and X = leaving group.
本发明涉及一种制备式(I)中的
吡罗砜和芬氧砜的直接前体的方法。该方法包括在没有光照射的情况下对苯基位置进行
溴化反应(步骤a),然后进行
硫酰化反应,以取代
溴原子(步骤b),并在去除保护基后,暴露的巯基或巯酸盐与在3位带有离去基团的取代
异噁唑啉发生反应(步骤c),其中Y = 保护基。在本发明的另一种变体中,通过首先通过适当的
硫化试剂将碳
硫键形成在2-
异噁唑啉的3位上,以取代3位的离去基团(特别是酸衍生残基,如
磷酰基,
硫酰基,卤素,
氰或羧基团),从而合成了
吡罗砜或芬氧砜的直接前体。生成的产物是S-保护的3-
硫代-2-
异噁唑啉,可以用碱处理以去除保护基,暴露出巯基或巯酸盐,随后可以与苯基甲基
溴反应,形成
吡罗砜或芬氧砜的直接前体。Ar = 芳基,Y = 保护基,X = 离去基团。