Flavonoids. 43 [1,2]. Deprotonation‐initiated aryl migration with sulfur dioxide extrusion: A route to 2,3‐dihydro‐2,3‐diaryl‐3‐hydroxy‐4H‐1‐benzopyran‐4‐ones

Abstract

AbstractTreatment of trans‐2,3‐dihydro‐2‐aryl‐3‐nosyloxy‐4H‐1‐benzopyran‐4‐ones with various bases afforded 2,3‐dihydro‐r‐2‐aryl‐t‐3‐hydroxy‐c‐(4‐nitrophenyi)‐4H‐1‐benzopyran‐4‐ones in a deprotonation‐initiated aryl migration followed by sulfur dioxide extrusion. In the presence of hydroxide and methoxide ions a secondary ring cleavage has also been observed. However, the reaction of trans‐2,3‐dihydro‐2‐aryl‐3‐nosyloxy‐4H‐1‐benzopyran‐4‐ones with cyanide ions gave 2,3‐dihydro‐r‐2‐aryl‐t‐4‐cyano‐c‐3,c4‐epoxy‐4H‐1‐benzopyrans in a carbonyl attack of cyanide followed by an internal substitution reaction.