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Synlett 2011(15): 2157-2162  
DOI: 10.1055/s-0030-1261200
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Microwave-Assisted and Yb(OTf)3-Promoted One-Pot Multicomponent Synthesis of Substituted Quinolines in Ionic Liquid

Anil Kumar*, V. Kameshwara Rao
Department of Chemistry, Birla Institute of Technology and Science, Pilani 333 031, Rajasthan, India
Fax: +91(1596)244183; e-Mail: anilkumar@bits-pilani.ac.in;
Further Information

Publication History

Received 13 April 2011
Publication Date:
31 August 2011 (online)

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Abstract

A straightforward and efficient method has been developed for the synthesis of quinolines by Yb(OTf)3 catalyzed three-component reaction of aldehydes, alkynes, and amines under microwave irradiation in ionic liquid. A series of 2,4-disubstituted quinolines was synthesized in excellent yield (69-93%) under mild reaction condition and the catalyst was recycled for four cycles.

Key words

microwave assisted - ytterbium triflate - one-pot - multicomponent - quinolines - ionic liquid

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Synthesis of 2,4-Diphenylquinoline (4a)
A mixture of benzaldehyde (106 mg, 1 mmol), aniline (93 mg, 1 mmol), phenylacetylene (102 mg, 1 mmol), and Yb(OTf)3 (62 mg, 10 mol%) was taken in a tube containing 2 mL of [bmim][BF4] and placed under MW irradiation in a CEM Discover BenchMate® reactor. The reaction parameters were set to 80 W, 80 ˚C for 3 min under stirring. After completion of the reaction, the reaction mixture was extracted with EtOAc-hexane (1:1, 3 × 10 mL). Evaporation of solvent gave the crude product which was purified by passing through a silica column to give pure 4a (253 mg, 90%) as an off-white solid; mp 108-110 ˚C (lit.¹6 109-111 ˚C).