Studies Of Synthesis Of Benzyl Esters Via Bidentate Group Directed Pd-Catalyzed C-H Bonds Activation

The construction of C-C bonds and C-X bonds has been an important research in organic chemistry. In the past few decades, transition-metal-catalyzed coupling reactions developed rapidly and have emerged as the powerful tools for the construction of C-C bonds and C-X bonds, such as Heck coupling reaction, Suzuki coupling reaction, Sonogashina coupling reaction, Stille coupling reaction and so on. However, these coupling reactions require prefunctionalization of substrates, such as halogenation and metalation, leading to multiple reaction steps and liberation of waste salts. In comparison, Construction of C-C bonds and C-X bonds through transition metal-catalyzed direct C-H bond activation is more efficient and clean. However, direct C-H bond activation faces many challenges: first, C-H bond has higher activation energy and is hard to be activated; second, there are many C-H bonds in an organic compound. How to achieve the efficient and selective C-H bond activation becomes a hot topic in this field. Lots of research has shown that directed transition metal-catalyzed C-H bond activation can improve reactivity and achieve selevtive C-H bond activation.Benzyl esters are important organic compounds and have been widely used in chemistry, pharmacy, material and so on. In general, the nucleophilic reactions of carboxylic acids and their derivatives with benzyl alcohols are reliable methods for the preparation of benzyl esters. However, these protocols require the prefunctionalization of substrates and often suffer from harsh reaction conditions. To overcome these disadvantages, much effort has been focused on transition metal-catalyzed esterification of alkylbenzene by C(sp3)-H bond activation. In this thesis, through bidentate group directed transition metal-catalyzed C(sp3)-H bond activation, we use 2-pyridyl acyl protected benzylamine and alkylbenzene as substrates achieved selective synthesis of benzyl esters. Benzylamine derivatives and alkylbenzenes bearing both electron-donating and electron-withdrawing groups reacted well under the optimized conditions given the desired products in moderate to good yields. This novel protocol displays high selectivity and wide substrates scope, which provides a concise and efficient way to synthesize benzyl esters. In addition, control experiments are performed to obtain insights into the reaction mechanism, and a plausible mechanism is proposed.