Oxidative rearrangement of pentaalkoxychalcones with phenyliodine(III) bis(trifluoroacetate) (PIFA): synthesis of (±)-10-bromopterocarpin and (±)-pterocarpin

The oxidative rearrangement of pentaalkoxychalcones using the hypervalent iodine compound, phenyliodine(III) bis(trifluoroacetate) (PIFA), has been examined. Treatment of 2,2′-bis(benzyloxy)-4′-methoxy-4,5-methylenedioxychalcone with PIFA gives a rearrangement product in low yield, but 2,2′-bis(benzyloxy)-3-bromo-4′-methoxy-4,5-methylenedioxychalcone yields the rearrangement product, which leads to (±)-bromopterocarpin and (±)-pterocarpin.