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Direct Aerobic Strategy for Synthesis of Imines via Alcohols and Amines Promoted by Ruthenium(II) (η 6 ‐ p ‐cymene) Complexes
Author(s) -
Manikandan Thimma Sambamoorthy,
Ramesh Rengan,
Shivalingegowda Naveen,
Krishnappagowda Lokanath Neratur
Publication year - 2018
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201800083
Subject(s) - ruthenium , chemistry , imine , denticity , catalysis , steric effects , ligand (biochemistry) , toluene , ketone , medicinal chemistry , organic chemistry , crystal structure , biochemistry , receptor
Abstract Neutral ruthenium(II) p ‐cymene complexes were synthesised by complexation of [Ru(η 6 ‐ p ‐cymene)(μ‐Cl)Cl] 2 with substituted methyl‐2‐pyrrolyl ketone benzhydrazone ligands in good yields. The characterization of the synthesised complexes was accomplished by analytical and spectroscopic techniques (FT‐IR, UV‐Vis, NMR, and ESI‐MS). Crystal structures of two of the complexes exhibited that the hydrazone ligand was bonded to ruthenium ion in a bidentate fashion via imine nitrogen and imidolate oxygen and witnessed ruthenium centered pseudo‐octahedral geometry. The catalytic feasibility of these Ru(II) complexes was explored for the direct aerobic synthesis of imine from the coupling of alcohols and amines in toluene medium with Cs 2 CO 3 as a base without molecular sieves or any additives. The scope and versatility of the present catalytic system were performed with the diverse range of alcohols and amines such as primary/secondary aromatic, aliphatic, heteroaromatic, cyclic as well as chiral substrates under open atmospheric condition. Further, the tolerance of steric and electronic effects on substrates was evaluated. Besides, the effect of promoters on the reaction including solvents, bases, temperatures and catalyst loading was carried out as well.