Chemistry of (E)‐2‐(2,4‐Dioxochroman‐3‐ylidene)‐2‐phenylacetonitrile: Access to Biscoumarin‐Fused Trioxabicycles

Abstract A series of biscoumarin‐fused 2,6,9‐trioxabicyclo[3.3.1]nona‐3,7‐dienes were synthesized from base‐mediated coupling of 4‐hydroxycoumarins with benzoyl cyanides and followed by treating with pyridine and thionyl chloride. The mechanism of this reaction was proposed to involve the formation of ( E )‐2‐(2,4‐dioxochroman‐3‐ylidene)‐2‐phenylacetonitrile as a key intermediate, which could further react with 2‐(2,4‐dioxochroman‐3‐yl)‐2‐hydroxy‐2‐phenylacetonitrile to yield biscoumarin‐fused trioxabicycles.