Palladium-Catalyzed Decarboxylative Ortho Sp~2C-H Bond Acylation Of O-Methyl Ketoximes

The formation of carbon-carbon, carbon-oxygen, carbon-halogen, carbon-nitrogen and carbon-sulfur bonds via transition-metal catalyzed C-H bond activation has been an important strategy for synthesizing orgranic compounds during the past years. Particularly, with being directed by coordinating ligands such as amide, pyridine and oximes, C-H bond activation can achieve higher selectivity and thus has recieved much attention today. Since ketone moiety has been known as a critical structural motif for preparing natural products, drugs and industrial materials, it is of high practical value to apply palladium catalyzed C-H bond acylation to synthesize aromatic ketones. Up to now，αoxocarboxylic acids, aldehydes, a-diketones, alcohols, toluene derivatives, etc. have been proven as efficient acyl sources.In order to further study C-H bond acylation, we have demonstrated the palladium-catalyzed decarboxylative ortho-acylation of O-methyl ketoximes. When using Pd(OAc)2as the catalyst, Na2S2O8and Ag2O as the oxidants and1,4-dioxane/HOAc (5:1, v/v) as the solvent,O-methyl ketoximes can react with a-oxocarboxylic acids to provide aromatic ketones. This protocol can be applied to a varitiey of O-methyl ketoximes and a-oxocarboxylic acids containing not only electron-donating but also electron-withdrawing groups with yields up to98%.