Synlett 2011(5): 689-693  
DOI: 10.1055/s-0030-1259555
© Georg Thieme Verlag Stuttgart ˙ New York

An Approach to Highly Functionalized Quinolines and Isoquinolines via a Gold-Catalyzed Benzannulation

Biswajit Panda, Jhuma Bhadra, Tarun K. Sarkar*
Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India
Further Information

Publication History

Received 22 November 2010
Publication Date:
11 February 2011 (online)


The AuCl3-catalyzed benzannulation of pyridine-­containing oxo-alkynes with external as well as internal alkynes proceeds under mild conditions, and a variety of quinoline and isoquinoline derivatives are produced in good to excellent yields. The reaction proceeds through the formation of aza-isobenzopyrylium auric ate complexes as evident from trapping experiments.

    References and Notes

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Indeed 1a was found to react exothermally when brought in contact with DMAD in DCE at a similar concentration.


Oxo-alkynes 1a-d were prepared from the corresponding pyridine-2-chloro aldehydes by Sonogashira coupling; similarly, 1e was prepared from iodoaldehyde 3 by Sonogashira coupling.


An alkyne with an aryl and an ester substituent, e.g., PhCºCCO2Me was found not to react either with the electron-rich oxo-alkyne 1a or the electron-deficient oxo-alkyne 1e; presumably in this case the HOMO-LUMO energy difference is too high for both pairs of reactants.


This Sonogashira coupling was unsuccessful (<10%) under the classical conditions [PdCl2(PPh3)2/CuI] using a variety of bases such as Et3N, i-Pr2NH, K2CO3, or NaHCO3.


Even carrying out the reaction at a lower temperature (0-15 ˚C) did not give any traces of the [3+2] product 6.