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

Under basic conditions 2,6-bis(bromomethyl)-4-pyrone 8 reacts with tetraeth ylene glycol to yield the unexpected macrocycle 9, which is related to the antibiotic Kjellmanianone 10. We propose that this ring transformation proc eeds 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, t he 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)-fura none derivative was confirmed by X-ray analysis.