Cyclisation of two key allyl phenol intermediates viz. 2-allyl-6-bromo-4-formyl phenol 1 and 4-acetyl-2-allyl-6-bromo phenol 2 has been studied under a variety of acid catalysts. While mineral and organic acids did not yield any cyclic products, polyphosphoric acid and 70% perchloric acid affected the cyclisation upto 55-70%. Significantly the cationic montmorillonite clays have been used for the first time and found to affect the regioselective cyclisation and yielded the five membered coumarans in quantitative yields.
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