A number of N-arylisoxazol-5(2H)-ones (aryl = phenyl, isoquinolin-1-yl, quinolin-2-yl, 2-phenylquinazolin-4-yl and benzothiazol-2-yl) have been reacted with lithium azide to give 2-(1-aryltetrazol-5-yl)acetic esters, which have been C- methylated and hydrolysed. The resulting 2-(1-aryltetrazol-5-yl) propanoic acids had low antiinflammatory activity, as judged by inhibition of synthesis of prostaglandin PGE2 or tumour necrosis factor α.
While isoxazol-5(2H)-ones substituted with heterocycles at C2 but unsubstituted at C3 react with amines to give either amidines or malonamides, their reaction at low temperatures with lithium dialkylamides is a preparatively useful procedure for obtaining the amidines in most cases. Longer reaction times may lead to formation of pyrimidin-4-ones when ester groups are present at C4 of the isoxazolone.