93669-50-2Relevant articles and documents
Pyrimidines. 7. A Study of the Chlorination of Pyrimidines with Phosphorus Oxychloride in the Presence of N,N-Dimethylaniline
Gershon, Herman,Grefig, Anthony T.
, p. 1161 - 1167 (2007/10/02)
The chlorination of 6-trifluoromethyluracils by phosphorus oxychloride in the presence of N,N-dimethylaniline was studied and compared with results obtained with 6-methyluracils. 6-Trifluoromethyluracils and its 5-chloro analog afforded moderate yields of the di- and trichloropyrimidines, accompanied by good yields of the 2-N-methylanilino by-products, after a 3-hour reaction time.After 24 hours, the 2-N-methylanilinopyrimidines were the primary or sole products.A small yield of 2,4-bis(N-methylanilino)-6-trifluoromethylpyrimidine was also obtained.The 6-methyluracils afforded high yields of the di- and trichloropyrimidines, after 3 and 24 hours, along with minor amounts of the 2-N-methylanilino by-products.After 48 hours, the proportion of 2,4-dichloro-6-methylpyrimidine decreased, and the 2-N-methylanilino product increased. 2-Chloro-4-methylanilino-6-methylpyrimidine and bis(2-N-methylanilino)-6-methylpyrimidine were also formed in small amounts.The chlorination products from 5-chloro-6-methyluracil remained constant over 188 hours of reaction time. It appears that the Π electron distribution around the ring, as influenced by the substituents, controls the course of the chlorination and by-product formation.Since the amination by a tertiary amine is a type of Hoffmann reaction, the presence of the chlorine in 5 position of the ring adds steric hindrance and thus enhances the regiospecificity of the formation of by-products.
