Pinacol Rearrangement of 3,4-Dihydro-3,4-dihydroxyquinolin-2(1H)-ones: An Alternative Pathway to Viridicatin Alkaloids and Their Analogs

摘要

3-Alkyl/aryl-3-hydroxyquinoline-2,4-diones were reduced with NaBH4 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 H_2SO_4, 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.