Pinacol rearrangement of 3,4-dihydro-3,4-dihydroxyquinolin-2(1H)-ones: An alternative pathway to viridicatin alkaloids and their analogs

Abstract

3-Alkyl/aryl-3-hydroxyquinoline-2,4-diones were reduced with NaBH 4 to give cis-3-alkyl/aryl-3,4-dihydro-3,4-dihydroxyquinolin-2(1H)- ones. These compounds were subjected to pinacol rearrangement by treatment with concentrated H2SO4, resulting in 4-alkyl/aryl-3- hydroxyquinolin-2(1H)-ones. When a benzyl (Bn) group was present in position 3 of the starting compound, its elimination occurred during the rearrangement, and the corresponding 3-hydroxyquinolin-2(1H)-one was formed. The reaction mechanisms are discussed for all transformations. All compounds were characterized by IR, 1H- and 13C-NMR spectroscopy, as well as mass spectrometry. Copyright © 2013 Verlag Helvetica Chimica Acta AG, Zürich.