Studies On Some Oxidative Coupling Reactions Mediated By Hypervalent Iodine(Ⅲ)Reagents

During the past decade, the hypervalent iodine compounds have attracted considerable interest of chemists and experienced an unprecedented development in organic chemistry. The hypervalent iodines are nowadays popular reagents not only for various oxidations, but also for the formation of carbon-carbon bonds, carbon-heteroatom bonds and heteroatom-heteroatom bonds. The activation of carbon-hydrogen bonds, rearrangements and fragmentations can also be induced by these reagents. Contrary to classical metal oxidants, the hypervalent iodine reagents are perfect with respect to the trend of modern chemistry, due to their high reactivity, enhanced stability, and environmentally benign nature. Among them, the trivalent iodines as versatile and powerful reagents could promote a series of chemical transformations in organic synthesis, and therefore the hypervalent iodine (Ⅲ) chemistry has been widely applied in the preparation of pharmaceutical precursors as well as in the total synthesis of natural products.I this dissertation, we mainly focused on the oxidative coupling reactions mediated by hypervalent iodine (Ⅲ) reagents, and made major investigations on (1) the oxidative coupling reactions of aromatic amines, (2) the asymmetric phenolic oxidative coupling, and (3) the application of phenolic oxidative coupling reactions in the synthetic studies of morphine.Part Ⅰ:Based on the literatures about the hypervalent iodine (Ⅲ) reagents, we summarized the reaction mechanisms and the research progress in the oxidative coupling reactions. Then studies towards the applications of hypervalent iodine (Ⅲ) reagents in organic chemistry were planned to carry out.Part Ⅱ:As a new application of oxidative coupling reactions mediated by hypervalent iodine (Ⅲ) reagents, the oxidative coupling of aromatic amines was investigated. Several oxidants, various solvents as well as different temperatures were screened. It was found that PIFA is especially effective for the transformation under mild conditions in high yields. In addition, we also preliminarily examined the competitive oxidative coupling reactions between aromatic amine and phenol.Part III:To expand the scope of oxidative coupling reactions mediated by hypervalent iodine (Ⅲ) reagents, three structurally novel chiral iodine compounds and a series of phenol-derived substrates were designed and prepared. Researches on the asymmetric phenolic oxidative coupling mediated by chiral iodine compounds were conducted preliminarily in a catalytic and stoichiometric fashion. Additionally, we also made a preliminary investigation on the 1,2-shift of phenyl group in the hypervalent iodine (Ⅲ)-promoted oxidation of styrene-type alkenes.Part IV:Inspired by the above phenolic oxidation, we presented a retrosynthesis of morphine, in which the hypervalent iodine (Ⅲ)-mediated phenolic oxidative coupling reaction was designed to access the synthetic precursor containing the C13 quaternary carbon. The structural modifications of phenol-derived substrates and the examinations on the oxidative coupling conditions were made, providing some preliminary efforts directed to the application of hypervalent iodine (III) chemistry in organic synthesis.