Design, Preparation, And Reactivity Of Hypervalent Iodine (Ⅲ) Compounds

During the past decade, the organic chemistry of hypervalent iodine compounds has experienced an unprecedented development. Hypervalent iodine reagents are nowadays popular reagents not only for the oxidation, but also for the formation of carbon-carbon bonds, carbon-heteroatom bonds, heteroatom-heteroatom bonds. Activation of carbon-hydrogen bonds, rearrangements and fragmentations can also be induced by these reagents. Therefore, hypervalent iodine compounds offer high potential for the improvement of known reactions, not only from the environmental point of view, they are also potentially interesting reagents for the development of completely new synthetic transformations.Despite their useful reactivity, enhanced stability, and environmentally benign nature, common hypervalent iodine reagents are not perfect with respect to the principles of Green Chemistry. The reactions of these stoichiometric reagents with organic substrates lead to Arl as the byproduct, which is difficult to recover and reuse because of its high volatility and solubility in organic solvents. In addition, typical reactions of common hypervalent iodine reagents are performed in non-recyclable organic solvent (dichloromethane, DMF, DMSO, etc.), which have potentially damaging environmental properties.In this dissertation, focused on the problems existed in the hypervalent iodine chemistry, applications of hypervalent iodine (Ⅲ) compounds in organic synthesis processes and their recycling approaches were investigated.Some novel, highly soluble, and reactive iodonium ylides bearing an ortho substituent on the phenyl ring are designed and prepared from substituted iodobenzene and malonate or dimedone. According to X-ray crystal graphy, these novel iodonium ylides show remarkable intramolecular I…O interaction, which decreased the intermolecular I…O interaction and the tendency to polymerize. Therefore, they are highly soluble in common solvent and show higher reactivity than the original phenyliodonium ylides in the Rh-catalyzed cyclopropanation, C-H insertion, transylidation and reaction with carbodiimides.As model reactions for the formation of carbon-heteroatom bonds, synthesis of nitriles and carbodiimides was then studied using hypervalent iodine (Ⅲ) compounds as reagents. It was found that, among various kinds of hypervalent iodine (III) reagents, HTIB is especially effective for these kinds of transformations. In the presence of HTIB and nitrogen source, alcohols, aldehydes and amines all converted to nitriles under mild conditions in high yields. The desulfidation of thiourea to carbodiimides also proceeded smothly under mild conditions in the presence of HTIB with high yields.Polymer-supported and magnetic nanoparticle-supported PhI(OAc)2were successfully prepared and their applications and recycle abilities in oxidation of alcohols were studied in detail. Results showed that these supported reagents have good stability and catalytic activities, and they could be easily recovered and reused without significant loss of activities.Catalyst oxidative systems using m-chloroperbenzoic acid, potassium peroxodisulfate, peracetic acid and hydrogen peroxide as co-oxidant were investigated. The applications of these systems in the oxidation of alcohols and the synthesis of benzimidazoles were explored.The development of aqueous-phase reactions using hypervalent iodine (Ⅲ) compounds was also investigated. Selective oxidation of alcohols can be achieved using iodosylbenzene or its derivative as oxidant in the presence of β-Cyclodextrin or potassium bromide. These systems offers several advantages, including mild reaction conditions, simple work-up procedure and more environmentally benign.