Investigations Of Pd/Cu Catalyzed C-H Functionalization Reactions

The constructions of C-C bond、C-O bond and C-N bond as the key part of organic compounds have been studied in the organic synthesis chemistry. In the past decades, the transition-metal catalyzed C-H functionlization as the efficient strategy for the construction of them have been widely developed because of the advantage of simple operation and atom-economy. Pd and Cu catalysts in the transition-metal catalyzed reaction are widely applied due to the property of inexpensive and low toxicity. In order to further expand their range of application in the C-H functionlization reaction, this dissertation studied the following contents, which include:1. We have develop a copper-catalyzed method for acyloxylation and amidation of sp2C-H bond using the pyridine as the directing group. The 2-arylpyridine as the preliminary substrates reacted with aldehydes% methylarene and amides respectively to generate the new C-C bond and new C-O bond under the Cu(OAc)2/TBHP catalytic system. In the reaction with aldehydes, not only the aromatic aldehydes but also the aliphatic aldehydes were suitable as well. The reaction could tolerate various functional groups, such as methyl, methoxyl, fluoro, chloro, bromo and nitro group. When oxygen was used as the oxidant, the reaction could also proceed smoothly, which suggested the reaction could be applied in the field of industry. The pathway of the reaction is possible that the aldehydes first was oxidized into the corresponding carboxylic acid, then the carboxylic acid undergoes the oxidative couping reaction with 2-arylpyridine. Similarly, methylarenes could also be oxidized into the corresponding aromatic aldehydes, then which could be further transformed into carboxylic acid to react with 2-arylpyridine for the formation of the new C-C bond. The reaction could afford 20%-42% yield. Under this catalytic system, the amides could react with 2-arylpyridine as well to construct the new C-N bond. Likewise, the reaction also tolerated various functional groups, such as methyl, methoxyl and chloro group. Aliphatic acetamide was also attempted and could afford moderate yield of terminal compound. Nicotinamide as a sort of heteroarene could also undergo the coupling reaction to generate desired product in low yield.2. We have develop a amidation reaction of acyl C-H bonds of aldehydes. The protocol uses 10 mol% of Pd(PPh3)2(OAc)2 as the catalyst,2 equiv of TBHP as the oxidant, acetonitrile as a solvent, and the amidation reaction could be efficiently performed under the mild condition. The reaction could afford 45%-81% yield of products, the reaction also tolerated various functional groups, such as methyl, methoxyl, fluoro, chloro and bromo group. The picolinoyl group was able to be selectively breaked away under the MeONa/MeOH system. The radical trapping experiment demonstrated aldehyde should participate in the coupling reaction in the species of acyl radical. The principle of this reaction possible is a sound contribution to the field.3. We have develop a C-arylation reaction of the sp2C-H bond of the heteroarene. The reaction could be efficiently performed under the mild condition using Cu(OAc)2 as a oxidant without the addition of any strong bases. The inexpensive arylsulfonyl hydrazide was applied as the aryl source. This reaction is insensitive to atmospheric moisture and oxygen, and neither dried solvents nor an inert atmosphere is required. Compared with other coupling reagents, this reaction is of practical application.