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In(OTf)₃-catalyzed synthesis of 2-styryl quinolines: scope and limitations of metal Lewis acids for tandem Friedländer annulation–Knoevenagel condensation

Author:
Dinesh Kumar, Asim Kumar, Mohammad Mohsin Qadri, Md. Imam Ansari, Abhishek Gautam, Asit K. Chakraborti
Source:
RSC advances 2014 v.5 no.4 pp. 2920-2927
ISSN:
2046-2069
Subject:
Lewis acids, acetoacetic acid, benzaldehyde, catalysts, catalytic activity, condensation reactions, quinoline, solvents
Abstract:
The catalytic potential of different metal Lewis acids has been assessed for the one-pot tandem Friedländer annulation and Knoevenagel condensation involving 2-aminobenzophenone, ethyl acetoacetate, and benzaldehyde to form 2-styryl quinoline under solvent free conditions. While various metal Lewis acids were effective in promoting the Friedländer annulation step, In(OTf)₃ was the only effective catalyst for the subsequent Knoevenagel condensation reaction suggesting In(OTf)₃ as the stand-alone catalyst for the tandem Friedländer–Knoevenagel reaction to form 2-styryl quinolines. The protocol is compatible with different variations of aromatic/hetero-aromatic aldehydes and α,β unsaturated aromatic aldehydes giving highly functionalized 2-aryl/heteroaryl vinyl quinolines. The catalyst can be recovered and reused to afford the desired product in very good to excellent yields.
Agid:
6669393