Selective mono-allylation of diphenyl ether with allyl bromide catalyzed by lead halo composite (Pb3BrF5/Pb3ClF5)

Allylation of diphenyl ether (DPO) with allyl bromide (ABr) was catalyzed by lead halo composite of the general formula Pb3XF5 (where X=Br or Cl) at 80°C. The reaction was carried out in a stirred glass reactor at atmospheric pressure with ABr and DPO (molar ratio of ABr:DPO=1:5) which gave mainly para-allyl DPO. Side reactions like isomerization of the double bond and cyclization of allylic functional groups were observed when allyl bromide was taken in excess. These products were p-1-propenyl DPO ‘oxepane’, ortho- and para-monoallyl DPO’s and p,p′-diallyl DPO. However, under the optimized reaction conditions, the allylation was more selective for para-allyl DPO. This implies that functional selectivity which is difficult to achieve in most cases, could be easily achieved with solid lead halo composite catalysts.