A simple and improved procedure for preparing multi-gram quantities of 2,2'-spirobi[2H-1-benzopyran] (2) is reported. The cyclization of the dihydroxybenzopyran intermediate (1) into 2 proceeded smoothly when a solution of 1 in 2-ethoxyethyl acetate was heated under reflux for 3 hours
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Muthiah N. Inbasekaran (1993) studied this question.
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