Magnetic Nanoparticle-Supported Iodoarene Oxidative Catalysts and Its Application to Phenol Oxidation
Iodoarene oxidative catalysts immobilized on magnetite (Fe3O4) were developed. The catalysts showed reactivities similar to that of 4-iodophenoxyacetic acid for the oxidation of 4-alkoxyphenols in the presence of Oxone® as a co-oxidant. In addition, they
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Abstract Iodoarene oxidative catalysts immobilized on magnetite (Fe3O4) were developed. The catalysts showed reactivities similar to that of 4-iodophenoxyacetic acid for the oxidation of 4-alkoxyphenols in the presence of Oxone® as a co-oxidant. In addition, they were easily recovered by the use of an external magnet and could be recycled up to eight times. The oxidation of various 4-alkoxyphenols with the catalyst proceeded smoothly at room temperature to give the corresponding p-quinones in good to high yields. This is the first example of a magnetic nanoparticle-supported iodoarene catalyst. Keywords Hypervalent compounds Oxidation Quinones
Magnetic properties
Nanoparticles
1 Introduction Environmentally benign procedures are required for the production of pharmaceuticals, flavors and fragrances, and agrochemicals. Hypervalent iodine compounds, trivalent iodine reagents such as phenyliodine(III) diacetate (PIDA) and phenyliodine(III) bis(trifluoroacetate) (PIFA), and pentavalent iodine reagents such as Dess–Martin periodinane (DMP) and o-iodoxybenzoic acid (IBX), have recently received significant attention as efficient, useful, and non-metallic oxidants in organic synthesis owing to their low toxicity, ready availability, and ease of handling (Fig. 1) [1–3]. With respect to the principles of green chemistry, hypervalent iodines are not ideal because stoichiometric amounts of iodine reagents are necessary during oxidation to produce equimolar amounts of iodine waste. Accordingly, many researchers have made efforts to overcome these disadvantages by two approaches: (1) use of easily recoverable and recyclable iodine reagents, H. Nambu I. Shimokawa T. Fujiwara T. Yakura (&) Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Sugitani 930-0194, Toyama, Japan e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2017 K. Tomioka et al. (eds.), New Horizons of Process Chemistry, DOI 10.1007/978-981-10-3421-3_9
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I
OCOCH3
I
OCOCH3
OCOCF3 OCOCF3
PIDA
PIFA
O
O
O I OAc AcO OAc
O I O OH
DMP
IBX
Fig. 1 Structures of hypervalent iodoarene reagents
recyclable polymer-supported hypervalent iodoarene reagents I(OCOR)2
PS
PS
O
O OH I O
O
PS = polystyrene R = CH3, CF3
I
O O
X
O
X = O, NH
recyclable nonpolymeric hypervalent iodoarene reagents
PS
Y
Y Me N
N BF4
Y
Y
Y
Y = I(OCOR)2
Y
Y
Y
I(OAc)2
(CH2)3C8F17 C8F17(CH2)3
I(OAc)2
Fig. 2 Structures of recyclable hypervalent iodoarene reagents
(2) developing catalytic versions of hypervalent iodine oxidation. (1) Two types of recyclable stoichiometric iodine reagents were reported, polymer-supported reagents [3, 4] and nonpolymer ones such as 1,3,5,7-tetraphenyladamantanederived, [5] tetraphenylmethane-derived [6], ion-supported [7, 8], and fluorous [9, 10] compounds (Fig. 2). Although the polymer-supported reagents can be easily recovered, they show much less reactive than the corresponding monomeric forms owing to steric hindrance of the reactive sites. On t
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