Shandong Weitai Fine Chemical Co. ,Ltd

Dibromo compounds, are important drug intermediates and key core structures commonly used in drug and material development. However, there are relatively few methods for the synthesis of such compounds with relatively stringent reaction conditions.

  A method for the preparative synthesis of dibrominated compounds using tribromooxyphosphorus with mild reaction conditions, simple operation, a single reaction product, simple post-treatment and high yield.

  The synthesis method comprises the following steps:

  Raw material 1 is heated in a solvent and reacted with sodium methanol to obtain intermediate 1. Intermediate 1 is mixed with a bromination reagent and heated to carry out the reaction. Upon completion of the reaction, the reaction solution is quenched and then extracted, and the resulting extracted solution is concentrated to obtain the dibrominated compound product, wherein x1 and x2 are independently selected from ch or n.

  As a preferred embodiment, in the following equation, x1 denotes n or ch and x2 denotes ch. Further preferably, x1 is n and x2 is ch.

  Preferably, in step (1) the solvent used in the reaction is any of methanol, ethanol or isopropanol, more preferably the solvent is methanol. Preferably, in step (1) the molar ratio of feed material 1 to sodium methanol is 1 : (2-4) and further preferably the molar ratio of feed material 1 to methanol salt is 1 : (2-3).

  Preferably, the bromination reagent is a mixture of one or more of tribromooxyphosphorus, tribromophosphorus, pentabromophosphorus, bromine and hydrobromic acid.

  In step (1), the heating reaction temperature is between 60°C and 120°C, preferably between 60°C and 70°C. Preferred embodiments, wherein the molar ratio of the intermediate 1 to the bromination reagent is 1 : (3-10), further preferably the molar ratio of the intermediate 1 to the bromide reagent is 1 : (5-10). Further preferably, the bromination reagent is tribromophosphorus, a mixture of tribromophosphorus and tribromophosphorus, or a mixture of tribromophosphorus and bromine.

  Dichlorinated compounds as feedstock, such as 2,6-dichloropyrazine, are first reacted with sodium methanol to form 2,6-dimethoxypyrazine. The methoxylated compound is then reacted with a brominating reagent to prepare a dibromo compound, such as 2,6-dibromopyrazine. The reaction conditions are mild and simple, with a single reaction product and a high yield of the target product. The target product can be obtained in high yield by simple post-treatment, and thus the process method is expected to be developed as an industrial production method.

  As shown in the above embodiments, the 2,6-dibromopyrazine product is obtained in high yield by simple post-treatment, especially when the bromination reagent is a mixture of tribromooxyphosphine and tribromophosphine.