A Convenient Synthesis of Oxazolines and Imidazolines from Aromatic Aldehydes with Pyridinium Hydrobromide Perbromide in Water
作者:Shinsei Sayama
DOI:10.1055/s-2006-941597
日期:2006.6
Various 2-oxazolines were prepared from aromatic aldehydes and 2-aminoethanol with pyridinium hydrobromide perbromide in water at room temperature. 2-Imidazolines were also obtained in good yields from aromatic aldehydes and ethylenediamine under the same reaction conditions.
Oxazoline is OK! A general and efficient method for the synthesis of oxazolines has been developed (see scheme). This allowed the preparation of 27 five‐membered‐ring heterocycles and 11 six‐membered‐ring heterocycles in moderate to good yields.
New octahedral ruthenium(II) complexes (1-4) have been synthesized from the reaction of ruthenium( II) precursors [RuHCl(CO)(EPh3)(3)] (E - P or As) with the bidentate Schiff base ligands, 2-((2,6-dimethylphenylimino) methyl) quinolin-8-ol (L-1) and 2-((2,6-diisopropylphenylimino) methyl) quinolin-8-ol (L-2) in ethanol. These complexes have been characterized by elemental analyses, IR, UV-Vis, H-1, C-13 and P-31 NMR and ESI-Mass spectroscopy. The molecular structure of the complex [RuCl(CO)(PPh3)(2)(L-2)] (2) was determined by single-crystal X-ray diffraction, which reveals a distorted octahedral geometry around ruthenium(II) ion. The catalytic activity of the new complexes was evaluated for the condensation of nitriles with ethanolamine under solvent free conditions. The processes were operative with aromatic and heteroaromatic nitriles and tolerated several substitutional groups. The studies on the effect of substitution over ligands, coligands, reaction time, temperature and catalyst loading were carried out in order to find the best catalyst in this series of complexes and favorable reaction conditions. A probable mechanism for the catalytic condensation of nitrile has also been proposed. The catalyst was recovered and recycled up to five times without significant loss of its activity. (C) 2015 Elsevier B.V. All rights reserved.