Deep eutectic solvent promoted one-pot synthesis of nitriles from alcohols
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J. Chem. Sci. (2020)132:122 https://doi.org/10.1007/s12039-020-01815-z
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Deep eutectic solvent promoted one-pot synthesis of nitriles from alcohols LUXIAO LIUa, HONG-YU ZHANGa, GUOHUI YINa, YUECHENG ZHANGa,b,* and JIQUAN ZHAOa,* a School
of Chemical Engineering and Technology, Hebei Provincial Key Lab of Green Chemical Technology and High Efficient Energy Saving, Hebei University of Technology, Tianjin 300130, People’s Republic of China b National-Local Joint Engineering Laboratory for Energy Conservation of Chemical Process Integration and Resources Utilization, Hebei University of Technology, Tianjin 300130, People’s Republic of China E-mail: [email protected]; [email protected] MS received 7 February 2020; revised 18 May 2020; accepted 14 June 2020
Abstract. Various aryl nitriles were readily synthesized from aerobic oxidation of substituted benzyl alcohols in deep eutectic solvent composed of choline chloride (ChCl) and p-toluenesulfonic acid (p-TsOH) in the presence of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), followed by condensation with hydroxylamine hydrochloride. High yields of corresponding nitriles have been obtained under mild reactions conditions. This strategy belongs to a novel and environmentally benign transition-metal-free one-pot cascade process for the synthesis of nitriles. Keywords. Deep eutectic solvent; benzyl alcohols; aryl nitriles; hydroxylamine hydrochloride.
1. Introduction Cyano is a vital group in organic chemistry as it plays a crucial role in pharmaceuticals, agrochemicals, dyes and other fine chemicals.1–3 In addition, nitriles can serve as precursors of amides, aldehydes, ketones, carboxylic acids, and heterocycles.4–7 Traditionally, aryl nitriles are synthesized through Sandmeyer reaction, which employs diazonium salts and highly toxic metal cyanides as raw materials,8 and alkylnitriles are prepared by the nucleophilic substitution of alkyl halides with a stoichiometric amount of alkali metal cyanides. However, there exist risks of poisoning and environmental pollution when using metal cyanides on a large scale. Over the past decades, a variety of procedures for the synthesis of nitriles have been developed, such as the dehydration of amides9 and aldoximes,10 the ammoxidation of aldehydes11 and primary amines,12 and amination-dehydrogenation of alcohols.13,14 Compared to other raw materials, alcohols are inexpensive and easily available, therefore, direct converting alcohols to nitriles has become an
attractive alternative recently. Mizuno et al., reported the synthesis of nitriles from ammoxidation of primary alcohols catalyzed by an alumina supported ruthenium hydroxide catalyst.15 Hu et al., used silica-supported functionalized ionic liquids as catalysts, such as FeCl4IL-SiO2, to promote the conversion of alcohols with ammonia to nitriles with H2O2 as an oxidant.16 A PSBHA-Cu system was developed by Molla et al., which permitted aerobic oxidation of alcohols with ammonium formate as nitrogen s
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