Joint Research on Chemistry of Hypervalent Compounds

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The research on hypervalent compounds is the one of the most important fields of organic chemistry. This research was conducted to aim at clarifying the roles of hypervalent compounds in organic reactions, especially, to develope new reactive hypervalent reagents and the synthetic reactions using the reagents.1.Development of Hypervalent ReagentsSynthesis of highly reactive hypervalent iodine reagents were conducted. The p-phenylene type of bisiodine (III) reagents was prepared from iodosylbenzene (PhIO) and trifluoromethanesulfonic acid (TfOH). Double the molar amounts of TfOH were essential to produce the p-phenylene reagent. Iodobenzenediacetate was converted by using 2 equiv of TFOH to a highly reactive iodine reagent. Also, o-iodosylbenzoic acid provided a highly reactive iodine reagent. These hypervalent iodine reagents showed a high reactivity to aromatic and acetylenic substrates to give aryl and alkynyliodoniumu salts in high yields.2.High Reactivity of Hypervalent Iodine CompoundsThe high reactivity of the hypervalent iodine reagents was attributed to the high nucleofugacity of triflate group attached with iodine. The electron withdrawing groups on the aromatic ring increased the reactivity. The high reactivity of hypervalent compounds toward nucleophiles was derived from the high leaving ability of the phenyliodonio group.3.Synthesis of Novel Hypervalent CompoundsThe highly reactive hypervalent reagents developed in this research provided many novel hypervalent compounds, such as (p-phenylene) bisiodonium salts, alkynyliodonium salts, diaryliodonium salts, aryl-and alkynyliodonium salts with carboxy group, 1-arylbenzothiophenium salts, and the related derivatives, in addition to liquid-crystalline diacetylenes and benzyne precursors.