Versatile Hypervalent‐Iodine(III)‐Catalyzed Oxidations with m‐Chloroperbenzoic Acid as a Cooxidant

Abstract

As oxidants, hypervalent iodine(iii) reagents are widely recognized as alternatives to highly toxic heavy-metal oxi-

Recycling and Catalytic Approaches for the Development of a Rare-Metal-Free Synthetic Method Using Hypervalent Iodine Reagent

“…18) According to our initial plan, the adamantane and methane-based iodoarenes 1Ј, which possess high reactivities and durability, are the most suitable as recyclable catalysts, and the catalytic use of 1Ј results in a more beneficial method. We carried out the reactions using 5 mol% of iodoarenes 1Ј resulting in a yield of product 4 nearly equal to the former cases ( Table 2, Xϭadamantane or methane); moreover, the catalysts could be recovered by the general procedures already shown in Chart 3 and repeatedly reused.…”

“…In the present spirolactam formation, TFE contributed to the generation of the highly reactive iodine(III) catalytic species as well as promoted the formation of the nitrenium ion intermediates leading to the products 6 by taking advantage of its excellent cation-stabilizing ability. 7) Since the reports of our catalytic strategy 18) and those of other research groups 40,41) in 2005, the representative types of hypervalent iodine-mediated oxidations are now due to the catalytic manner of the organoiodines but mostly limited to the construction of C-O bonds as the bond-forming process. Thus this spirolactam-forming method developed by us is the first and only example to utilize the catalytic strategy for performing effective carbon-nitrogen bond-forming reactions using iodoarenes as organocatalysts to provide the key intermediates of naturally occurring alkaloids.…”

“…[11][12][13][14][15][16][17] By applying the unique regeneration method of the recyclable reagents 1, we next succeeded in the catalytic use of hypervalent iodine reagents, which led to the effective utilization of the reagents as "organocatalysts." [18][19][20][21] Furthermore, we challenged the asymmetric oxidations as being very difficult with hypervalent iodines and have achieved the highly selective catalytic oxidations of phenols for the first time by designing a new chiral reagent 2Ј. 22) Through such research, the possibility of hypervalent iodines as environmentally friendly alternatives not only to heavymetal oxidants but also even to rare metals became realistic.…”

Speedy and Clean Hypervalent Iodine/Nitroxyl Radical Mediated Oxidation of Alcohols Using Recyclable Adamantane Reagent with Highly Active 2-Azaadamantane-<i>N</i>-oxyl Organocatalyst

“…Furthermore, the reagent could be nearly quantitatively recovered after the reactions by utilizing the insolubility of the formed tetraiodide 1′ in a polar solvent, specifically, methanol. Based on these significant advantages, the adamantane reagent 1 would serve as a recyclable and greener alternative to conventionally-used hypervalent iodine reagents, and mediate many types of oxidation reactions with efficiencies similar to those of phenyliodine diacetate (PIDA), [29][30][31][32][33][34][35][36] while the workup for the recovery of the reagent usually requires three separate steps, that is, i) evaporation of the reaction solvent, ii) precipitation by adding methanol, and then iii) filtering.Hence, the procedure to recover the tetraiodide 1′ started with the removal of the dichloromethane solvent under reduced pressure by a rotary evaporator, and the tetraiodide 1′ should be then precipitated by adding methanol to the resulting residue. Aimed at realizing a more practical procedure for the hypervalent iodine/nitroxyl radical oxidation of alcohols, we have further designed a more simplified and faster system that can skip the above mentioned precipitation steps, i) and ii), which are reported in this paper (Chart 1).…”

“…Furthermore, the reagent could be nearly quantitatively recovered after the reactions by utilizing the insolubility of the formed tetraiodide 1′ in a polar solvent, specifically, methanol. Based on these significant advantages, the adamantane reagent 1 would serve as a recyclable and greener alternative to conventionally-used hypervalent iodine reagents, and mediate many types of oxidation reactions with efficiencies similar to those of phenyliodine diacetate (PIDA), [29][30][31][32][33][34][35][36] while the workup for the recovery of the reagent usually requires three separate steps, that is, i) evaporation of the reaction solvent, ii) precipitation by adding methanol, and then iii) filtering.…”