The chemistry of the highly reactive 2,6-bis (bromomethyl)-4-pyrone

Under basic conditions 2,6-bis(bromomethyl)-4-pyrone 8 reacts with tetraethylene glycol to yield the unexpected macrocycle 9, which is related to the antibiotic Kjellmanianone 10. We propose that this ring transformation proceeds via the cyclopropyl intermediate d (Scheme 2), which undergoes a ring opening reaction comparable to the Favorskii rearrangement. Also, 8 reacts with methanol/sodium methoxide to yield the 3(2H)-furanone derivative 11, the formation of which is suggested to proceed via the intermediate ii with a carbenium-oxonium-ion subunit (Scheme 3). The structure of the 3(2H)-furanone derivative was confirmed by X-ray analysis.