Process for producing allyl bromides

#1. Field of the Invention

#The present invention relates to an improved process for producing allyl bromides useful in the field of synthetic organic chemistry, in particular, as intermediates for producing fine chemical products, such as agricultural chemicals, medicines, dyes, etc.

#2. Description of the Prior Art

#The process of the present invention will further be explained hereinbelow.

#The present inventors have carried out studies in search of a method for effectively converting allyl chlorides into allyl bromides by using metal bromides in relatively small quantities. As a result, it has now been found that certain solvents, for example, N,N-dimethylformamide, N,N'-dimethylimidazolidinone, etc., are a good solvent for metal bromides but a poor solvent for the corresponding metal chlorides, and that when the halogen exchange is carried out in one of such solvents, the desired reaction proceeds under mild conditions without requiring a co-catalyst, thereby producing the corresponding allyl bromide in high yield, and that after separated from the allyl bromide formed and any unreacted allyl chloride therefrom by distillation, the reaction solvent can be recycled into the reaction system without any further purification.

#For example, where allyl bromide is produced from allyl chloride, using N,N-dimethylformamide as the solvent and 1.2 moles of sodium bromide as a halogen exchanging agent per mole of allyl chloride, the reaction proceeds smoothly at 40.degree. C. to give the desired allyl bromide in a yield of about 90%, forming no substantial by-products. After the sodium chloride is filtered off and the unreacted allyl chloride and the desired allyl bromide are removed by distillation, the N,N-dimethylformamide which remains as a still residue can be used again in the halogen exchange reaction without further purification and gives reaction results not significantly different from those wherein fresh N,N-dimethylformamide is employed.