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(1 H )‐ones. These compounds were subjected to pinacol rearrangement by treatment with concentrated H 2 SO 4 , resulting in 4‐alkyl/aryl‐3‐hydroxyquinolin‐2(1 H )‐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(1 H )‐one was formed. The reaction mechanisms are discussed for all transformations. All compounds were characterized by IR, 1 H‐ and 13 C‐NMR spectroscopy, as well as mass spectrometry.