The direct methoxylation of substituted phenylalanines has been accomplished via methoxyiminoacyl (MIA)−mediated Pd−catalyzed C−H functionalization. A diverse array of ortho−methoxylated phenylalanine derivatives is efficiently generated in good to high yields. KIE study has shown that the oxhydryl cleavage step is the rate−limiting step. The computational data show that the participation manner of methanol has a great influence on the energy barriers of transition states during the C(sp2)−O formation stage. The pathway containing stepwise deprotonation and reductive elimination is superior to that of a concerted deprotonation-methoxylation.

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