The products obtained when α-(o-nitrophenylthio) acids are reduced by means of sodium borohydride and palladium–charcoal depend on (a) the reaction temperature, (b) the solvent, (c) the length of time in which the α-(o-nitrophenylthio) acid is in contact with the reducing agent, and (d) the nature of the substituents on the α-(o-nitrophenylthio) acid. By varying these conditions, benzothiazine hydroxamic acids (i.e. substituted 3,4-dihydro-4-hydroxy-3-oxo-2H-1,4-benzothiazines), the corresponding lactams (3,4-dihydro-3-oxo-2H-1,4-benzothiazines), and derivatives of 2-carboxymethylthioazobenzene can be prepared.In two cases, additional products were obtained. When (o-nitrophenylthio)acetic acid was catalytically reduced for 30 min in dioxane, 3,4-dihydro-3-oxo-2H-1,4-benzothiazine-1,1-dioxide (VIc) was an unexpected product, and when α-(4-trifluoromethyl-2-nitrophenylthio)-isobutyric acid was left for a prolonged time in contact with sodium borohydride and palladium–charcoal, a derivative of hydrazobenzene, namely, 2-carboxy(α,α-dimethyl)methylthio-5-trifluoromethylhydrazobenzene (V), was one of the three identified products.
当α-(邻硝基苯硫基)酸通过钠硼氢化物和钯-活性炭还原时,所得产物取决于(a)反应温度,(b)溶剂,(c)α-(邻硝基苯硫基)酸与还原剂接触的时间长短,以及(d)α-(邻硝基苯硫基)酸上取代基的性质。通过改变这些条件,可以制备苯并噻嗪羟肟酸(即取代的3,4-二氢-4-羟基-3-氧代-2H-1,4-苯并噻嗪)、相应的内酰胺(3,4-二氢-3-氧代-2H-1,4-苯并噻嗪)以及2-羧甲基硫偶氮苯的衍生物。在两种情况下,还得到了额外的产物。当(o-硝基苯硫基)乙酸在二恶烷中催化还原30分钟时,意外产生了3,4-二氢-3-氧代-2H-1,4-苯并噻嗪-1,1-二氧化物(VIc);当α-(4-三氟甲基-2-硝基苯硫基)-异丁酸与钠硼氢化物和钯-活性炭长时间接触时,其中一种三个确定的产物是苯肼的衍生物,即2-羧甲基(α,α-二甲基)甲硫基-5-三氟甲基苯肼(V)。