Microwave-Assisted Copper Slag-Catalyzed Green S -Arylation of Arenethiols with Arylboronic Acids
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icrowave-Assisted Copper Slag-Catalyzed Green S-Arylation of Arenethiols with Arylboronic Acids A. P. Sarkatea,*, D. S. Gavanea, B. D. Kalea, K. S. Karnika, I. S. Narulaa, A. L. Khandareb, A. P. Rajhansa, and V. S. Jambhorkara a
b
Department of Chemical Technology, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad, 431004 India
Department of Food Toxicology, Food & Drug Toxicology Research Center, National Institute of Nutrition, Hyderabad, Telangana, 500007 India *e-mail: [email protected] Received February 25, 2020; revised February 27, 2020; accepted February 29, 2020
Abstract—Diaryl sulfides have been synthesized in moderate to excellent yield by S-arylation of arenethiols with arylboronic acids using copper slag as a catalyst. Copper slag is a by-product obtained from smelting and refining of copper. Conventional heating method has been compared with the microwave-assisted technique. The proposed microwave-assisted synthesis provides excellent yields of diaryl sulfides in a short time (10 min) and is ligand-free, green, and cost-effective. Keywords: copper slag, waste material, catalyst, microwave irradiation, S-arylation, green chemistry
DOI: 10.1134/S107042802007026X INTRODUCTION Heteroatom groups play an important role in organic synthesis and therapeutic applications [1]. Compounds containing C–S bonds are widely used in pharmaceutical and materials science [2]. Many catalytic reactions have been performed in the past with efficient yields. The use of catalysts containing nanomaterials, transition metals, acid catalysts, and palladium compounds made it difficult to optimize the reaction to an economic path [3–7]. Green or sustainable chemistry implies utilization of waste materials to provide environmentally friendly synthetic routes. Copper slag, a by-product of copper smelting and refining, has become a problem for industries [8].
Thousands of tons of copper slag are being disposed as solid waste every year [9]. Dumping or disposal of this waste creates environmental pollution [10]. Considering the application of copper slag, it is used as fine aggregate in cement mortars and normal concrete [11]. Copper slag contains oxides of silicon, iron, copper, lead, and magnesium, and it can be efficiently used as a catalyst in many coupling reactions like S-arylation. Microwave-assisted techniques replace conventional methods of synthesis in terms of yield, reaction time, and green methodology with less amount of byproducts [12–17]. In continuation of our previous studies [1, 5, 18], herein we report the microwave-assisted copper slagcatalyzed synthesis of substituted diaryl sulfides.
Scheme 1. OH X R1
B
OH
HS
i or ii
+
X
S
R1
R2 1a–1i
R2 3a–3j
2a, 2b
1, X = CH (a–g, i), N (h); R1 = H (a, h), 4-Me (b), 4-MeO (c), 4-HO (d), 4-Cl (e), 4-Br (f), 2-MeO (g), 4-NC (i); 2, R2 = H (a), MeO (b); 3, X = CH (a–g, i, j), N (h); R1 = H (a, h), 4-Me (b, i), 4-MeO (c), 4-HO (d), 4-Cl (e), 4-Br (f), 2-MeO (g), 4-NC (j); R2 = H (a–h), MeO (i, j). Reaction conditions: i: conventional synthesis: copper s
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