Reaction of 4-hydroxy-2-quinolones with thionyl chloride-preparation of new spiro-benzo[1,3]oxathioles and their transformations

Abstract

4-Hydroxy-2-quinolones (1) react with thionyl chloride to give new spiro-benzo[1,3]oxathioles (3) and bis(4-hydroxy-2-quinolone-3-yl)sulfides (2) and small quantities of 3-chloro-4-hydroxyquinolin-2-ones (4). Compounds 3 afford sulfides 2 by heating in different solvents and [1,4]oxathiino[3,2-c:5,6-c']di-quinoline-6,8(5H,9H)-diones (6) by reaction with triphenylphosphine. The reconversion of compounds 2 to 3 was achieved using bromine. The reaction mechanisms are discussed for all transformations. All compounds were characterized by IR, H-1, and C-13 NMR (in some cases also N-15 NMR) spectroscopy, and EI and/or ESI mass spectrometry. The X-ray structure was determined for compound 3b. (c) 2012 Elsevier Ltd. All rights reserved.