The preparation (scheme 1) starts from Cefditoren pivoxil (24.83g, 0.04mol), formalin (3.48g, mass fraction are 37%~40%) and sulfuric acid (0.12g, 1.2mmol), which is added in acetonitrile (125mL), and keeping the temperature 80℃ for 2.0h, then the reaction solution is cooled down to room temperature. The solution is added the mixture of purified water (100mL) and ethyl acetate (200mL) and keep stirring 10min after liquid separation. After being filtered, purified and recrystallized, the finished dimer was got with yield 87.6%.
Scheme 1 The synthesis of Cefditoren Pivoxil Dimer
Zhangying and his coworkers developed another method to cefditoren pivoxil dimer.
Scheme 2 The synthesis of Cefditoren Pivoxil Dimer
Scheme 2 shows the reaction mechanism. First, the cephem compounds (1) nucleophilic attack of the amino Vilsmeier reagent (1), to generate intermediate (3); another molecule cephem compound (I) followed by nucleophilic attack of the amino group resulting intermediate (3) to generate intermediate (5); and then the intermediate (5) dimethylamine off, to form the intermediate (6), the generates the desired products (7) by the transfer of hydrogen ions.
