5\u2010Oxazolones, IV. Reactions of 5(4H)\u2010oxazolones with triphenylphosphonium methylides

The Wittig reaction of ethyl (triphenylphosphoranylidene)acetate (2a) with the carbonyl group of trisubstituted 5(4H)-oxazolones 1a\u2013c afforded ethyl 5(4H)-oxazolylideneacetates 3a\u2013c and triphenylphosphane oxide. Starting from oxazolones 1d\u2013i and ylide 2a, methyleneoxazoles 3d, e and ethyl 5-oxazoleacetates 4a\u2013f were obtained besides ylides 5a\u2013e deriving from the nucleophilic attack of the ylide at 1 and subsequent opening of the oxazole ring. Oxazolones 1a\u2013c reacted also with triphenylphosphonium phenylmethylide (2b) to yield methyleneoxazoles 3f,g and ylides 5f\u2013h. By treating triphenylphosphonium methylide (2c) and -methoxymethylide (2d) with 1a\u2013c only open-chain compounds 5i\u2013k and 5l\u2013n, respectively, were obtained