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 Catalysis Ru(Cl)-Salen Complex: Solvent Selective Homogeneous Catalyst for One-Pot Synthesis of Nitriles and Amides Pravin N. Borase + , Pranila B. Thale + , and Ganapati. S. Shankarling* [a] An efficient protocol for direct transformation of aldehydes into of nitrile and amide derivatives using Ru(Cl)-salen complex as a solvent selective homogeneous catalyst is developed. The catalyst has also been explored for hydration of nitrile to synthesize the primary amides in an aqueous medium. Addi- tionally, a mechanistic pathway for the dehydration of aldoxime to nitrile and hydration of nitrile to amide was studied using gas chromatography. The catalyst has been fully characterized by using spectroscopic techniques such as IR spectroscopy, MALDI-TOF mass analysis and 1 H NMR technique. A simple work up procedure, lower catalyst to substrate ratio, and good to excellent yields of the products, higher turnover number and turnover frequency makes the protocol more advantageous and feasible. 1. Introduction Environmentally benign selective transformations of various functional groups in organic chemistry can be achieved using organometallic ruthenium catalysts. [1–3] These are widely used in metathesis reactions, dihydroxylation of olefins, oxidative dehydrogenation of alcohols and much more. [4–6] Owing to its high stability in air and in numerous solvents, ruthenium based catalysts exhibit higher selectivity and tolerance towards various functional groups. [7–10] Recently, Che et al have demon- strated a remarkable catalytic property of salen based ruthe- nium complex for alkene cyclopropanation [11] and aldehyde olefination [12] with ruthenium (II) salen catalyst have been reported by Kuhn et al. Since salen ligands possess a good chelating affinity towards many metal ions numerous applica- tion of tetradentate salen ligands are known in coordination chemistry and catalysis. [13–18] Considering these advantages, herein, we have designed a salen based novel organometallic ruthenium complex and its synthetic utility has been demon- strated for the selective transformation of aldehydes into nitriles and primary amides. The development of greener and efficient synthetic routes for the synthesis of nitriles and amides has been a long sought interest. [19–23] They are important precursors in the synthesis of nitrogen containing heterocyclic compounds and often serve as the versatile building blocks in the synthesis of bioactive products, such as nitrilosides, peptides and proteins. [24–26] They are widely used as intermediates in the industry for manufac- turing polymers, agrochemicals, pharmaceuticals, lubricants and detergents. [27–29] Generally, nitriles can be synthesized by substitution reaction of alkyl and aryl halides with metal cyanides, oxidation of primary amines or dehydration of aldoximes with various dehydrating agents. [30–32] Whereas, amides are usually synthesized by condensation of carboxylic acids and their derivatives such as acyl chloride, anhydride or ester with various amines. [33,34] There are other alternative routes available for the synthesis of amides such as amino- carbonylation of olefins, hydroamination of alkynes [35,36] and hydration of nitriles [37,38] Schmidt reaction, [39,40] Beckmann rear- rangement [41] and amidation of thioacids with azides. [42] It must be noted that most of these synthetic methods suffer limitations such as high temperature, need of stronger Bronsted or Lewis acids, use of toxic and corrosive reagents, lower atom economy and harsh reaction conditions. To date, very few reports are available for direct transformations of aldehydes to primary amides. [37,38,43] The first report on the catalytic conversion of aldoxime into primary amide by using Wilkinson’s complex is reported by Chang and co-workers. [44] Later, individual research groups have reported various metal catalyst such as iridium, [45] ruthenium [46] and palladium. [43] Cadierno et al have reported the amide formation using organometallic ruthenium complex in water as solvent. Similarly, Ramesh and co-worker have also reported the ruthenium catalyzed transformation of aldehyde to primary amide in acetonitrile as solvent. [47,48] Copper di-acetate [49] and triethylamine [50] have also been reported as a homogeneous catalyst for amide formation. Despite the advances accom- plished by these protocols, there are few inadequacies such as a higher catalyst to substrate ratio, longer reaction time and lower isolated yields. Along with this, the major challenge is to get the control over the formation of undesirable carboxylic acids and nitrile byproducts. To overcome above limitations, Ru(Cl)-salen complex is found to be a highly efficient and solvent selective homogenous catalyst for the direct trans- formation of aldehydes to primary amides and nitriles. [a] Dr. P. N. Borase, + Dr. P. B. Thale, + Prof. G. S. Shankarling Department of Dyestuff Technology, Institute of Chemical Technology, Matunga, Mumbai 400 0019 (India) E-mail: gs.shankarling@gmail.com [ + ] These authors contributed equally. Supporting information for this article is available on the WWW under https://doi.org/10.1002/slct.201800121 Full Papers DOI: 10.1002/slct.201800121 5660 ChemistrySelect 2018, 3, 5660 – 5666  2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim