Thermal Rearrangement of 5-(2-Hydroxy-6-oxocyclohexyl)-5<i>H</i>-chromeno[2,3-<i>b</i>]pyridines

Abstract

Some of the most important transformations in organic chemistry are rearrangement reactions, which play a crucial role in increasing synthetic efficiency and molecular complexity. The development of synthetic strategies involving rearrangement reactions, which can accomplish synthetic goals in a very efficient manner, has been an evergreen topic in the synthetic chemistry community. Xanthenes, pyridin-2(1H)-ones, and 1,6-naphthyridines have a wide range of biological activities. In this work, we propose the thermal rearrangement of 7,9-dihalogen-substituted 5-(2-hydroxy-6-oxocyclohexyl)-5H-chromeno[2,3-b]pyridines in DMSO. Previously unknown 5,7-dihalogenated 5-(2,3,4,9-tetrahydro-1H-xanthen-9-yl)-6-oxo-1,6-dihydropyridines and 10-(3,5-dihalogen-2-hydroxyphenyl)-5,6,7,8,9,10-hexahydrobenzo[b][1,6]naphthyridines were synthesized with excellent yields (90–99%). The investigation of the transformation using 1H-NMR monitoring made it possible to confirm the ANRORC mechanism. The structures of synthesized compounds were confirmed by 2D-NMR spectroscopy.

Keywords

• rearrangement
• NMR study
• chromeno[2,3-<i>b</i>]pyridine
• dimethyl sulfoxide
• 2,3,4,9-tetrahydro-1<i>H</i>-xanthene
• 5,6,7,8,9,10-hexahydrobenzo[<i>b</i>][1,6]naphthyridine