ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Synthesis and keto-enol tautomerism of ethyl 4-oxo-3,4-dihydro-1H-pyrano[3,4-b]quinoline-3-carboxylate

Ming-Qin Chang, Feng Gao, Yang Li, and Wen-Tao Gao

Institute of Superfine Chemicals, Bohai University, Jinzhou, 121000, China

E-mail: bhuzh@163.com

Abstract: An efficient method has been developed for the synthesis of a novel β-keto ester-containing pyranoquinoline compound, i.e., ethyl 4-oxo-3,4-dihydro-1H-pyrano[3,4-b]quinoline-3-carboxylate. The method entails a two-step synthesis. The first step involves the Williamson-type reaction of ethyl 2-bromomethyl-3-quinoline-3-carboxylate with ethyl hydroxyacetate in anhydrous benzene to afford the intermediate ethyl 2-[(2-ethoxy-2-oxoethoxy)methyl]quinoline-3-carboxylate. The second step includes the Dieckmann condensation reaction of the resulting intermediate in the presence of sodium ethoxide in anhydrous toluene to afford the desired pyranoquinoline containing β-keto ester moiety. Keto-enol tautomerism of the compound thus obtained was investigated by spectroscopic methods.

Keywords: pyranoquinoline – β-keto ester – Williamson-type reaction – ethyl hydroxyacetate – Dieckmann condensation – keto-enol tautomerism

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-012-0276-6

Chemical Papers 67 (4) 437–443 (2013)