Non-Pincer-Type Arene Ru(II) Catalysts for the Direct Synthesis of Azines from Alcohols and Hydrazine under Aerobic Conditions

Abstract

An efficient tandem synthetic approach to azines from the coupling of alcohols and hydrazine hydrate catalysed by newly synthesized arene Ru(II) complexes has been described. Two arene ruthenium(II) N-(pyrimidin-2-ylcarbamothioyl)furan-2carboxamide complexes have been fully characterised by analytical and spectral methods. The structures of the complexes have been confirmed with the aid of single-crystal X-ray analysis. The unprecedented coordination modes of N-(pyrimidin-2ylcarbamothioyl)furan-2-carboxamide ligand and the formation of four and six membered N,S-chelate complexes have been observed for the first time. Further, the new Ru(II) complexes act as an efficient catalyst for the synthesis of symmetrical azines. A diverse range of azines was synthesized. The products were isolated in good to excellent yields using a catalyst loading of 0.5 mol %. The catalytic reaction operates under aerobic and mild reaction conditions with the release of water as the only by-product. Plausible mechanism has been proposed and it is believed that the reaction proceeds initially via an aldehyde intermediate.

Iron-Catalyzed Metal–Ligand Cooperative Approach toward Sustainable Synthesis of Azines and N-Acylhydrazones in Air

“…Two well-defined Fe­(II) complexes [Fe­(L 1 )­Cl 2 ] ( 1 ) and [Fe­(L 2 )­Cl 2 ] ( 2 ) of the tridentate redox noninnocent azo-aromatic pincers 2-((4-chlorophenyl)­diazenyl)-1,10-phenanthroline ( L 1 ), and 2-(phenyldiazenyl)-1,10-phenanthroline ( L 2 ), respectively, are used as catalysts (Scheme ). − Catalysts 1 and 2 are two five-coordinate Fe­(II) complexes, wherein one tridentate azo-aromatic scaffold ( L 1/2 ) and two chlorido ligands are coordinated to the Fe­(II) center.…”

Arene Ru (II)‐catalyzed facile synthesis of N‐acylhydrazones via acceptorless dehydrogenative coupling strategy

“…As expected, no N ‐acylhydrazone formation was observed, which supports that the synthesis of N ‐acylhydrazone occurs via dehydrogenation of benzyl alcohol (Scheme 5 ‐ii ). On the basis of the previous reports, [ 16 ] we wished to examine the product selectivity (Scheme 5).…”

“…To the best of our knowledge, there is no report available on the metal‐mediated synthesis of N ‐acylhydrazones from alcohols and benzohydrazides. In continuation of our quest to develop new catalysts for the C–N bond forming reactions, [ 16 ] herein we report the direct synthesis of N ‐acylhydrazones using 0.5 mol% catalyst loading.…”

NNO Pincer Ligand-Supported Palladium(II) Complexes: Direct Synthesis of Quinazolines via Acceptorless Double Dehydrogenative Coupling of Alcohols

“…In continuation of our research on the catalytic behavior of organometallic complexes for various cross-coupling reactions, , herein, we report a sequential acceptorless dehydrogenation approach for the synthesis of quinazoline derivatives from readily available alcohols and 2-aminobenzyl alcohol by pincer-type palladium catalysts using ammonium acetate as a nitrogen source for the first time. Our protocol can be considered as more atom-economical and environmentally benign as the present scheme releases water and hydrogen as the only byproducts.…”