On the nitration of 2-pyrone

A 1:1 adducl of 2-pyrone and nitronium fluoroborate has been delected by nmr and is a possible precursor of 5-nitro-2-pyrone, a subsequently formed product. From comparison of the nmr spectra of the 1:1 adduct and 2-methoxypyrylium fluoroborate, the adduct is believed to be the pyrylium fluoroborate derived from nitration of the carbonyl oxygen of 2-pyrone.