Derivate von 4,5-dihydroxypyridonen durch ringerweiterung

The epimeric bromoghydrins 13/14 as well as their ethers 5/6 rearrange in the presence of silver ions to the 5-hydroxypyridones 15 or their ketals 9 respectively. with the bromohydrin ethers 5/6a and b this transformation is effected also with sodium methoxide. Under these reaction conditions the ring expansion is presumend ot proceed via bicyclic aziridines of which 7 could be issolated, The N-methylated compounds 5c/6c which cannot react likewise, form with sodium methoxide the 6-methoxypyridone 12 .