Reaction of Styrene with Chlorine Dioxide

ISSN 1070-3632, Russian Journal of General Chemistry, 2018, Vol. 88, No. 4, pp. 825–828. © Pleiades Publishing, Ltd., 2018. Original Russian Text © I.V. Loginova, I.Yu. Chukicheva, A.V. Kuchin, 2018, published in Zhurnal Obshchei Khimii, 2018, Vol. 88, No. 4, pp. 679–682. LETTERS TO THE EDITOR Reaction of Styrene with Chlorine Dioxide I. V. Loginova*, I. Yu. Chukicheva, and A. V. Kuchin Institute of Chemistry, Komi Scientific Center, Ural Branch, Russian Academy of Sciences, ul. Pervomaiskaya 48, Syktyvkar, Komi Republic, 167000 Russia *e-mail: Received November 2, 2017 Abstract—Reaction of styrene with chlorine dioxide under various conditions selectively produces 1-phenyl2-chloroethanone, with 1-phenyl-2-chloroethanol, 2-hydroxy-1-phenylethanone, (1,2-dichloroethyl)benzene, (2-chloro-1-phenyl)ethene, and (1,2,2-trichloroethyl)benzene isolated as reaction byproducts. Keywords: 1-phenyl-2-chloroethanone, 1-phenyl-2-chloroethanol, 2-hydroxy-1-phenylethanone, (1,2-dichloroethyl)benzene, (2-chloro-1-phenyl)ethene, (1,2,2-trichloroethyl)benzene DOI: 10.1134/S1070363218040308 sulfoxides [11–13] and quinones [14–16]. There are examples of using chlorine dioxide for oxidation of unsaturated compounds, giving a complex mixture of chlorination products [17, 18]. Chlorine dioxide was found to epoxidize styrene in aqueous solutions [19]. The monochlorine monoxide thereby formed then oxidized chlorine dioxide to chlorate and was reduced to hypochlorous acid. The end products included styrene oxide resulting from the reaction of hypochlorous acid with styrene and compounds formed via epoxide ring opening. Considerable amounts of styrene oxide were obtained when the oxidation was carried out at pH 6. Upon adding sulfamic acid the yields of the chlorinated products decreased substantially. Chloroketones and chlorohydrins are versatile intermediate products in synthesis of bioactive compounds [1]. Hydroxyketones are used for the synthesis of pharmaceuticals and fragrances and also are employed as fungicides, wood disinfectants, stabilizers of proteins and polyhydroxy compounds, reagents in analytical chemistry, etc. [2]. Similar styrene derivatives also have found extensive application. Chloroacetophenone is a toxic lacrimator which is synthesized either by chlorination of acetophenone or by the reaction of benzene with chloroacetyl chloride in the presence of anhydrous aluminum chloride [3]. Styrene chlorohydrin, a semiproduct in industrial synthesis of a synthomycin, is obtained by hydroxychlorination of styrene with calcium hypochlorite or by passing gaseous chlorine through an emulsion of styrene and water, whereby a part of styrene is converted to 1-phenyl-1,2-dichloroethane, difficultly separable from chlorohydrin [4]. The formation of 1-phenyl-1,2-dichloroethane can be avoided by carrying out the reaction of bromobenzene with anhydrous chloroacetaldehyde in the presence of magnesium metal, followed by hydrolysis of magnesium bromoalkoxide [5]. When carrying out the reaction of styrene with ClO2 we varied the technique of supplying ClO2, the styrene-ClO2 molar ratio (1 : 1, 1 : 2), and the catalyst [VO(acac)2, FIBAN K-1 sulfonic cation-exchange resin, KSF clay]. A ClO2-air mixture was bubbled through styrene or a solution of styrene in an organic solvent (CH2Cl2 or DMF), or, alternatively, a solution of ClO2 in H2O or in CH2Cl2 was added dropwise to styrene. The reaction was run at 20°C until complete conversion of styrene was achieved; the reaction products were separated by column chromatography. Here we studied the reaction of styrene with chlorine dioxide under various conditions. Chlorine dioxide is used for oxidation of alcohols [6, 7], sulfur-containing amino acids [8], and thiols and disulfides [9, 10], as well as for the preparation of variously structured Our results showed that, under the actual conditions, the reaction of styrene with ClO2 gave a mixture of compounds, chief among which are chloroketone 1 and chlorohydrin 2 (Scheme 1). 825 826 LOGINOVA et al. Scheme 1. Cl Cl 8 O 7 HO 1 6 2 5 3 ClO2 4 OH 3 2 1 Cl Cl Cl O + H 4 H H 5 The reaction run with the use of an aqueous solution of ClO2 at an equimolar ratio of the reactants gave 1-phenyl-2-chloroethanone 1 in a maximum yield of 69%, with up to 25% of 1-phenyl-2-chloroethanol 2 and up to 6% of 2-hydroxy-1-phenylethanone 3 formed as well. As the molar ratio of the reactants increased, the yield of 1 increased (81%), probably, due to oxidation of the hydroxy group in 2 to ketone with an excess of ClO2. On changing the solvent from water to CH2Cl2 the yield of 1 did not exceed 55%, and that of 2, 5%. The presence in the reaction mixture of (1,2-dichloroethyl)benzene 4 (23%) and of (2-chloro-1-phenyl)ethene 5 (17%) is explained by the formation of chlorine molecules from ClO2 decomposition in an aprotic solvent. Bubbling ClO2-air mixture through a solution of styrene in CH2Cl2 led to a similar set of reaction products. In a DMF medium styrene was oxidized with ClO2 predominantly to 1 with no formation of other chlorination products. As the consumption of the oxidant increased the yield of 1 increased to 75%. Bubbling ClO2 directly through styrene led to the formation of 1–3 in approximately equal amounts (20– 24%). The catalysts tested in the reaction of styrene with chlorine dioxide included VO(acac)2, FIBAN K-1, and KSF clay. FIBAN K-1 is a fibrous strongly acidic cation-exchange resin with SO3H+ functional group, whose polymer base is formed by polypropylene fiber with graft styrene-divinylbenzene copolymer. This is an effective catalyst for olefin isomerization, alcohol dehydration, and redox reactions [20, 21]. Montmorillonite KSF is a solid Lewis acid; H2SO4 may H Cl Cl Cl Cl 6 occur on its surface. VO(acac)2 is employed as a catalyst for epoxidation of allyl alcohols [22]. The use of the catalysts tested did not lead to selective oxidation of styrene; in all cases the amounts of chlorination products 4 and 5 increased. Also, (1,2,2-trichloroethyl)benzene 6 (1%) was isolated from the reaction catalyzed by VO(acac)2, unlike the reaction run under other conditions. The structures of 1–6 were confirmed by IR and NMR spectroscopy; the characteristics of the compounds synthesized corresponded to the published data [23–27]. (2-Chloro-1-phenyl)ethene 5 is a mixture of trans(5a) and cis-isomers (5b) which we could not separate chromatographically. The ratio and yield of the isomers formed were estimated from the integrated intensities of the signals from methine protons at C7 and C8 atoms in the 1H NMR spectrum at 6.68 and 6.88 ppm for (trans-2-chloro-1-phenyl)ethene 5a and at 6.33 and 6.73 ppm for (cis-2-chloro-1-phenyl)ethene 5b. According to the NMR data, the cis- and transisomers were in a 1 : (4–8) ratio. The 1H NMR spectrum of (1,2,2-trichloroethyl)benzene 6 exhibited signals from protons of two methine groups appearing as doublets at 5.28 and 6.07 ppm, as well as signals (...truncated)