Furan derivatives, substituted in the p-position, are not easily accessible. A simple route leading to such compounds is the reaction of an oxazole A with an acetylenic dienophile B which affords a nitrile C and a p-substituted furan derivative!, 2 D. Authors, who carried out this reaction previously, chose either symmetrical dienophiles (B: R2= R4= COOCH3, C6HS)! or, though they used unsymmetrical dienophiles (B: R3= H, R4= COOH, COCH3), ...
