100mmol of asarone reacted in the usual oxone manner, gave some 70mmol of sweet smelling, very crude viscous brownish-orange epoxide that was turned into ugly brown tar by H2SO4 hydrolysis that yielded nothing when trying to form the bisulfite adduct.
Chromic, the reason why Uemura takes for asarone different routes than for the other propenylbenzenes is easy: asarone (and most of its derivates) are very very acid sensitive. You just got a victim of this fact. And you made the right to proposal to follow: rearrangement by EtOAC/LiBr! Uemura would first destille the crude epoxide in the highest possible vacuum you can achive, not going over 170DegC. Make sure you get rid of any acid trace in the crude product. (170DegC temp should be on the save side before the thermal rearragment may start)
OR
Slowly heat the crude product and hope that about 200DegC the thermal rearragement takes place. Uemura would do this first with a small amount of the crude product in a test tube, slowly heated in an oil bath.
Let us know on the outcome!
Post 208300 (missing)
(Sonson: "2,3-DM-4,5-MD-P-2-P", Methods Discourse).