Stereoisomerization of α-hydroxy-β-sulfenyl-α,β-dimethyl naphthoquinones controlled by nonbonded sulfur–oxygen interactions

The anti α-hydroxy-β-sulfenyl-α,β-dimethyl naphthoquinones isomerize in basic media into syn/anti mixtures of isomers, giving the syn isomer as the major product. Conversely, anti α-hydroxy-β-alkoxy-α,β-dimethyl naphthoquinones isomerize to furnish the anti isomer as the major product. The crystal structure of syn α-hydroxy-β-phenylsulfenyl-α,β-dimethyl naphthoquinone has been determined. The X-ray and experimental work demonstrated that an attractive 1,4 intramolecular interaction of divalent sulfur with hydroxyl oxygen is the driving force for the aforementioned stereochemical preference.