Bromo-carbonyl chloride prodn. from corresp. acid and anhydride - by reaction with bromine and phosphorus tri:bromide, and then with chlorine

摘要

Prodn. of 2-4C bromocarbonyl chlorides (I) comprises reacting the corresp. carboxylic acid and its anhydride with (a) PBr3 and Br2, then (b) with Cl2. The mole ratio acid:anhydride:PBr3:Br2:Cl2 is 1:2:1:1:15. Pref. the first stage is at -10 to 20 degrees C and subsequent chlorination at 65-95 degrees C but below the b.pt. of (I). Readily available starting materials are used (known methods start from the bromocarboxylic acid) and no special safety precautions are needed. Both steps are carried out in a single reactor without isolation of the intermediate.