“…When the reaction is performed in the presence of pyridine, the product is a 1,4dihydroxybenzene whose 2-position bears the chromen-3-yl substituent; as there is a pyridinium group in the 3-position, the compound is a zwitterionic inner salt (Zhang et al, 2004). For the reaction of 4,7-dihydroxycoumarin and p-benzoquinone, the product is not a disubstituted p-benzoquinone as postulated (Rani & Darbarwar, 1987), but is a disubstituted pdihydroxyphenol. The compound crystallizes from dimethylformamide (DMF) as a trisolvate, (I) (Fig.…”