1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 z Organic & Supramolecular Chemistry Monochlorotriazinyl-β-cyclodextrin Grafted on Graphene Oxide as an Attractive Green Heterogeneous Nanoreactor for Selective Oxidation Reaction with NBS in Water Shadi Rasoul Pour, [a] Mohammad Dinari, [a] and Amir Abdolmaleki* [a, b] Graphene oxide supported monochlorotriazinyl-β-cyclodextrin (GO-MCT- β-CD) as a green nanoreactor was synthesized via a simple chemical bonding method and analyzed by XRD, FT-IR, CHNS, FESEM and Raman spectroscopy. The prepared GO-MCT- β-CD worked as a nanoreactor for the green oxidation reactions of benzyl alcohol derivatives with N-bromo succinimide to their corresponding aldehydes under green conditions. Depending on the different substituents of various benzyl alcohols, good to excellent yields were obtained and no over-oxidation was observed. It can be considered an attractive methodology due to the use of water in the presence of “solid metal-free nanoreactor” as a green reaction system at the room temper- ature. Easy separation and excellent reusability of the catalyst were other advantages of this methodology. Introduction Nowadays, green chemistry has been becoming an important issue in both industrial and academic research. [1] Thus, introducing environmentally gentle synthetic strategies has been the main target of today’s researchers. Among different strategies, using supramolecular compounds as organic reac- tors for reaction in aqueous media (as green and environmental friendly solvents) is really interesting. [2] During the past decades, the applications of supramolecular host-guest chemistry are of fascinating interest. The 2016 Nobel Prize in chemistry was awarded to organic chemists for the synthesis of molecular machines based on supramolecular interaction through reversible formation of host–guest complexes [3,4] Host molecules can form inclusion complexes with guest molecules, providing the selective and reversible interaction by non- covalent intermolecular bonds and, finally, release the products and regenerate the reagents for a new run. [5,6] β-Cyclodextrin (β-CD) is a cone-shaped cyclic oligomer that consists of seven α-linked D-Glucopyranose units joined from ‘‘head to tail’’. It has a hydrophobic nanocavity at the center and hydrophilic outside edge, which can form non-covalent reversible host- guest complexes with a variety of suitably sized aliphatic and aromatic molecules, preferably in water. [7,8] This property makes β-CD an interesting compound in organic synthesis as a nanocatalyst and nanoreactor since it is a water-soluble natural material, non-toxic, inexpensive, and metabolically safe. [9,10] The use of water as a green, gentle, safe, and inexpensive solvent (compared with organic toxic solvents) in the oxidation reactions is of importance to develop safer manufacturing protocols. [11] Water as a solvent is limited because of the insolubility of starting materials “in the water”. [12–14] On the other hand, the high solubility of β-CD in water, restricts its catalytic application in the aqueous dissolution, motivating chemists to develop a water-insoluble β-CD (but water- dispersible) in a solid state. A general strategy is the attach- ment of β-CD via chemical linkers to solid supporting materials. [15,16] Native β-CD cannot form a direct covalent bond with solid supports. Monochlorotriazinyl-β-cyclodextrin (MCT-β- CD), the first cyclodextrin derivative in the industrial scale, solves this problem. It was presented in 1996, possesses on average two to three monochlorotriazinyl groups on β-CD as the reactive anchor, and can create covalent bonds with nucleophilic groups on supports. [16–19] There are some reports in the literature concerning the potential of applications of these types of compound in organic reactions. [20–22] Cyclodextrins are commonly immobilized on different supports and covalent immobilization is considered one of the most frequently used ones. Among different support for immobilization, GO has attracted more attention recently. The abundant number of functional groups (carboxyl, carbonyl, hydroxyl, and epoxide) at the surface and edges of GO facilities its functionalization. In addition, functionalized graphene oxide causes easy adsorption of aromatic reactant by a strong π-π stacking interaction between GO sheet and aromatic rings of the reactant. [23,24] These types of supported reactors have been applied to several important organic reactions in the aqueous dissolution. [25–29] The oxidation of benzyl alcohol and its derivatives to their respective aldehydes is an important reaction in organic chemistry. Traditional processes through heavy metal-based catalysts are costly and cause environ- mental pollution due to the exhausting separation of the soluble catalysts. [17] Most of them give low yield as well as poor selectivity and are commonly available in organic solvents and [a] S. R. Pour, Dr. M. Dinari, Dr. A. Abdolmaleki Chemistry group, Pardis College, Isfahan University of Technology, Isfahan 84156–83111, I.R. Iran E-mail: abdolmaleki@cc.iut.ac.ir [b] Dr. A. Abdolmaleki Department of chemistry, College of science, Shiraz University, Shiraz 71467–13565, I.R. Iran Supporting information for this article is available on the WWW under https://doi.org/10.1002/slct.201900962 Full Papers DOI: 10.1002/slct.201900962 6390 ChemistrySelect 2019, 4, 6390 – 6396 © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim