The reactions of N-acyl-N-benzyl-α-amino acids (1) or N-acylprolines (5) with trifluoroacetic anhydride in the presence of pyridine afford 5-trifluoromethyloxazoles (2 or 7) in good yields. The reaction could proceed through the transient formation of mesoionic 1, 3-oxazolium-5-olates, followed by oxazolium salts.
在
吡啶存在下,N-酰基-N-苄基-
α-氨基酸(1)或N-酰基脯
氨酸(5)与
三氟乙酸酐反应,以良好产率得到5-三
氟甲基
噁唑(2或7)。该反应可能通过形成暂态的介离子1,3-
噁唑-5-醇盐,随后形成
噁唑盐盐类而进行。