Synthesis of 2-aryl- and 2-hetaryloxazoles from the oxazolines and oxazolidines

Treatment of 2-phenyl-, 2-(2-furyl)-, and 2-(2-thienyl)oxazolines with nickel peroxide has been found to give, in addition to the dehydrogenation products (2-substituted oxazoles), the fragmentation products (amides of benzoic, furan-2-carboxylic, and thiophen-2-carboxylic acids). This fragmentation appears to give initially the nitriles, which are then converted into the amides by the nickel peroxide. Catalytic dehydrogenation of 2-phenyloxazoline gives low yields of 2-phenyloxazole, the principal product being benzonitrile. Treatment of the Schiff's bases obtained from ethanolamine and aldehydes (benzaldehyde, furfural, and thiophen-2-aldehyde) with nickel peroxide gives trace amounts of the oxazoles, the principal products being the aldehydes, with smaller amounts of the nitriles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 822–825, June, 1986.