摘要:
Lithiation of N-pivaloyl-3,4-difluoroaniline (1a) with a slight excess of 2 mole equiv of n-butyllithium followed by methylation was studied. The reaction was found to be useful for either the selective methylation of 3,4-difluoroaniline or the synthesis of benzoxazole derivatives, depending on the reaction temperature. In the reaction of N-pivaloyl-3-chloro-4-fluoroaniline (1b) and N-pivaloyl-3-fluoroaniline (1c), the reaction proceeded rather sluggishly but benzoxazole formation predominated.