Synthesis 2005(6): 977-985  
DOI: 10.1055/s-2005-861850
PAPER
© Georg Thieme Verlag Stuttgart · New York

Oxidative Free Radical Cyclization of 2-(Ethoxycarbonylmethyl)-1,4-naphthoquinone Derivatives

Hui-Li Chen, Chien-Yu Lin, Yu-Chih Cheng, An-I Tsai, Che-Ping Chuang*
Department of Chemistry, National Cheng Kung University, Tainan, Taiwan 70101
Fax: +88(66)2740552; e-Mail: cpchuang@mail.ncku.edu.tw;
Further Information

Publication History

Received 25 October 2004
Publication Date:
09 March 2005 (online)

Abstract

A manganese(III)-mediated oxidative free radical cyclization of 2-(ethoxycarbonylmethyl)-1,4-naphthoquinone derivatives is described. These starting 2-(ethoxycarbonylmethyl)-1,4-naphthoquinones can be synthesized effectively from the reaction of corresponding 1,4-naphthoquinones with ethyl nitroacetate. With 2-benzyl-3-(ethoxycarbonylmethyl)-1,4-naphthoquinones, naphthacene-5,12-diones were produced effectively in high selectivity. With ethyl 2-benzoyl-3-(ethoxycarbonylmethyl)-1,4-naphthoquinones, in addition to the expected 6-hydroxynaphthacene-5,12-diones, the novel naphtho[2,3-c]furan-4,9-diones were also formed as the major product.