Structural reassignment of the dehydration product of 2′‐Hydroxywarfarin

The base catalyzed condensation reaction between 4‐hydroxycoumarin and o‐hydroxybenzal‐acetone yields 6‐methyl‐6,12‐methano‐6 H ,12 H ,13 H ‐[1]benzopyran[4,3‐ d ][1,3]benzodioxocin‐13‐one as the product rather than 6‐oxo‐7‐(2‐oxopropyl)‐6 H , 7 H ‐[1]benzopyrano[4,3‐ b ][1]‐benzopyran as had been previously postulated.