Research On Aldehyde Or Ketone Involved DCC Reactions

During the past decades, tremendous efforts have been put into researching and developing most efficient methods to build C-C bonds. Due to its efficiency and environmentally friendliness, transition metal catalyzed C-H activation reaction has become the focus of organic chemists and been considered as the new generation of C-C bond construction. After Li’s group introduces directly connecting two different C-H bonds under oxidative conditions to form C-C bonds selectively as dehydrogenative cross-coupling (DCC), organic chemists work day and night to discover new DCC reactions. These DCC reations provide waste-minimized synthetic alternatives to classic coupling procedures which rely on the use of prefunctionalized starting materials. Our group has also put some efforts on researching new DCC reactions.This dissertation mainly contains the following sections.The first chapter is a mini review on DCC reaction. According to the type of hybrid orbitals of C-H bonds, we emphatically introduce new research reports on DCC reactions between sp3 C-H and sp3 C-H bonds、sp3 C-H and sp2 C-H bonds、sp3 C-H and sp C-H bonds、sp3 C-H and P(O)-H bonds、sp2 C-H and P(O)-H bonds、sp C-H and P(O)-H bonds during the past few years, briefly introduce new DCC reactions between sp2 C-H and sp2 C-H bonds、sp C-H and sp C-H bonds.The second chapter is about a copper-catalyzed dehydrogenative cross-coupling reaction between unactivated ethers and simple ketones mediated by pyrrolidine. Under the catalysis of CuBr2 and in the presence of pyrrolidine, either tetrahydrofuran or tetrahydropyran can react smoothly with a series of methylaryl ketones to give desired coupling products using TBHP as an oxidant. The advantages of the dehydrogenative cross-coupling reaction are adoption of unmodified ethers as substrates, good tolerance of many functional groups and use of cheap copper salt as a catalyst. Unsatisfactorily, simple chain ethers, like diethyl ether can’t react in this catalyze system. A plausible radical mechanism through enamine attack is proposed.The third chapter is about a dehydrogenative cross-coupling reaction between allylic C-H bonds and the α-C-H bond of ketones or aldehydes was developed using Cu(OTf)2 as a catalyst and DDQ as an oxidant. This synthetic approach to γ，δ-unsaturated ketones and aldehydes has the advantages of broad scope for both ketones and aldehydes as reactants, mild reaction conditions, good yields and atom economy. A plausible mechanism using Cu(OTf)2 as a Lewis acid catalyst was also proposed.The fourth chapter introduces a novel DCC reaction between aromatic aldehydes or ketones and H-phosphonates has been developed for the synthesis of p-formyl or p-acylphenylphosphonates. The synthetic method has excellent para regioselectivities, good yields, and broad substrate scopes and is more benign to the environment. The DCC reaction also tolerates many functional groups, and results in a series of new p-formyl and p-acylphenylphosphonates, which should be important building blocks for the synthesis of versatile arylphosphonate derivatives.