A unique site-selective reaction of ketones with new recyclable hypervalent iodine(iii) reagents based on a tetraphenylmethane structure

Dohi, Toshifumi; Maruyama, Akinobu; Yoshimura, Motomu; Tohma, Hirofumi; Shiro, Motoo; Kita, Yasuyuki

doi:10.1039/b501475a

Cited by 61 publications

(29 citation statements)

References 25 publications

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“…To overcome these drawbacks of conventional polymer-supported reagents, the authors designed unique molecules 1 with admantane or methane cores to which four active iodine(III) sites are effectively attached, as new recyclable reagents (Chart 3). 11,12) All of 1a and its acid derivatives 1b and 1c are stable solids. They are soluble in typical organic solvents (for example, dichloromethane, acetonitrile, methanol, etc.)…”

Section: Development Of New Methods For Recycling and Catalytic Use Omentioning

confidence: 99%

“…In this project, we first developed the new recyclable reagents 1 that do not show any degradation of the backbones throughout their reuse and recovery processes. [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.…”

Section: Introductionmentioning

confidence: 99%

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

Dohi

2010

CHEMICAL & PHARMACEUTICAL BULLETIN

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Oxidation reactions consist of a number of important transformations in organic synthesis. However, in spite of their utility in both laboratory-and industrial-scale production, oxidations are among the most problematic processes regarding the factors of safety, environmental friendliness, operational simplicity, etc. As oxidants, hypervalent iodines, such as phenyliodine(III) diacetate (PIDA) and phenyliodine(III) bis(trifluoroacetate) (PIFA), are among promising reagents for developing environmentally benign oxidation reactions due to their low toxicities, mild reactivity, ready availability, high stability, and easy handling. Our research objective is, largely in consideration of economic and environmental viewpoints, to enhance the synthetic values of these reagents as useful alternatives to highly toxic heavy-metal oxidants and even rare transition metals by pioneering their efficient utilization methods and unique reactivities. During this study, we have succeeded in the development of new recyclable reagents 1 and their catalytic utilization, and the design of a new chiral reagent 2 and its application to perform asymmetric oxidations. Accordingly, the recycling and catalytic use of a hypervalent iodine reagent became possible in many representative types of oxidative bond-forming reactions, some of which even include key transformations for natural product synthesis. A summary of these important achievements in hypervalent iodine chemistry are described in this review.

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Section: Development Of New Methods For Recycling and Catalytic Use Omentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Dohi

2010

CHEMICAL & PHARMACEUTICAL BULLETIN

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“…Recyclable tetraphenylmethane-based reagents were subsequently developed by the same research group, and also proved useful in the α-sulfonyloxylation of ketones. [40] Biphenyl and terphenyl-based HTIB reagents were reported by Moroda and Togo in 2006. [41] These reagents demonstrated comparable reactivity to 4-(diacetoxyiodo)toluene and 4-[(hydroxy)(tosyloxy)iodo]toluene, but with the benefit of being easily recovered by filtration of the reaction mixture.…”

Section: Recyclable Reagentsmentioning

confidence: 99%

α-Functionalization of Carbonyl Compounds Using Hypervalent Iodine Reagents

Merritt¹,

Olofsson²

2010

Synthesis

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“…Thus, the reaction process and workup have become faster and cleaner compared to the previous method 24) utilizing acetonitrile as the solvent. Having proved the AZADO catalyst as a good counterpart of the recyclable adamantane reagent 1 for the alcohol oxidations, we then tested the generality of the catalytic system for an extended number of alcohols 2, typically employed for the hypervalent iodine/nitroxyl radical mediated oxidations, 24,25) as test substrates using the established experimental procedures. Encouraged by the excellent catalytic activity of AZADO in comparison to the alternative TEMPO in Table 1, we tried to use a lower amount of AZADO (5 mol%) in this screening (Tables 2, 3).…”

mentioning

confidence: 99%

“…[14][15][16][17][18][19][20][21][22][23] Regarding this interest, we have recently reported a versatile and clean method based on the use of the adamantanetype recyclable hypervalent iodine reagent 1 [24][25][26] (Fig. 1) for the organocatalytic oxidation of alcohols to aldehydes and ketones.…”

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confidence: 99%

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

Dohi

Kamitanaka

Mochizuki

et al. 2012

CHEMICAL & PHARMACEUTICAL BULLETIN

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By utilizing a specific solvent and highly active 2-azaadamantane-N-oxyl (AZADO) as an organocatalyst, we have improved the recycling protocol of the adamatane reagent 1 to be faster and more operationally simple for the hypervalent iodine/nitroxyl radical mediated alcohol oxidation. This very mild system can efficiently mediate the oxidation of a range of alcohols to carbonyl compounds with a broad substrate scope, and after the reactions, the reduced adamantane tetraiodide 1′, which automatically precipitated from the reaction mixtures as the reactions progresses, could be directly recovered by filtration.Key words alcohol oxidation; speedy process; recycling; hypervalent iodine reagent; nitroxyl radicalThe development of an efficient and clean method for the oxidation of alcohol functionalities to carbonyl groups remains an important topic widely investigated in modern synthetic chemistry.1-3) Among the present methods, the combination of the hypervalent iodine reagent [4][5][6][7][8] and nitroxyl radical catalyst, 9,10) which was first suggested by Piancatelli and Margarita's research group in the literature, 11) has gained particular attention in the past decades as a mild and metal-free versatile oxidation system. Due to the salient features of the catalytic conditions as well as the exclusive chemoselectivity toward alcohols in the presence of many oxidation-sensitive functional groups, this mild organocatalytic system has been frequently used for the selective oxidation of alcohol groups in complex molecules, [4][5][6][7][8] as represented by the early examples which appeared in the total synthesis of natural products, such as discodermolide and leucascandrolide A.12,13) Moreover, significant advances have been developed to date for the reagent and catalyst recycling, making the strategy and method even more attractive. [14][15][16][17][18][19][20][21][22][23] Regarding this interest, we have recently reported a versatile and clean method based on the use of the adamantanetype recyclable hypervalent iodine reagent 1 [24][25][26] (Fig. 1) for the organocatalytic oxidation of alcohols to aldehydes and ketones.27,28) The well-defined tetrahedral structure and sufficient interatomic distances between the iodine(III) sites in the molecule of the adamantane 1 are due to its higher reactivity and good solubility in solvents compared to the conventional polymer-supported reagents. Also, it is very stable under severe oxidative conditions, and the degradation of the molecule did not occur even after many recyclings. 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] w...

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A unique site-selective reaction of ketones with new recyclable hypervalent iodine(iii) reagents based on a tetraphenylmethane structure

Abstract: We have synthesized new recyclable reagents having a tetraphenylmethane backbone and used them in the site-selective alpha-tosyloxylation of ketones.

Cited by 61 publications

References 25 publications

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

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

α-Functionalization of Carbonyl Compounds Using Hypervalent Iodine Reagents

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

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