Stereochemistry of the reduction of α-chloroketones with sodium borohydride—application to 3-chloroquinoline-2,4-diones: Dedicated to the memory of Professor Dr. Vojeslav Štěrba who died in September 2015 being nearly 93 years old

Abstract

3-Chloroquinoline-2,4-diones were reduced with sodium borohydride to give syn- and anti-chlorohydrins, the stereochemistry of which was established by NMR spectroscopy. Both stereoisomeric chlorohydrins were reacted with potassium carbonate in methanol. anti-Isomers afforded the corresponding epoxides or rearranged to 3-hydroxy-4-alkylquinolin-2-ones, whereas syn-isomers did not react. However, these isomers converted to 4-hydroxyquinolin-2-ones after standing for a long period of time in DMSO. After reaction with thionyl chloride, the syn-isomers yielded cis- and trans-3,4-dichloroquinolin-2-ones. © 2016 Elsevier Ltd