The preparation and reactions of stable phosphorus ylides derived from maleic anhydrides, maleimides or isomaleimides

A number of stable triphenylphosphoranylidenesuccinimide derivatives have been prepared from maleimides or isomaleimides and triphenylphosphine. Also a stable ylide has been obtained from citraconic anhydride and triphenylphosphine. The succinimide ylides were found to react with a wide variety of aldehydes giving the corresponding ylidene derivatives in high yields. Although these triphenylphosphoranylidenes did not react with ketones, a tri-n-butylphosphoranylidene derivative did react with cyclohexanone to give a cyclohexylidenesuccinimide. In contrast, the recently discussed triphenylphosphoranylidenesuccinic anhydride reacts with cinnamaldehyde or phenylpropopargyl aldehyde to give the corresponding diylidene succinic anhydrides (fulgides). Intractable mixtures were obtained with the other aldehydes investigated. Furthermore, the stable ylide derived from triphenylphosphine and N-phenylmaleimide gives a ketenimine with phenyl or methyl isocyanate or phenyl isothiocyanate. The resulting ketenimines react with amines or benzenethiol to give diaminoethylene derivatives (ketenaminals) or a phenylthioaminoethylene derivative, respectively. Also, this phosphorus ylide reacts with nitrosobenzene to give 3-anilino-N-phenylmaleimide. The synthetic utility of these stable phosphorus ylides is discussed as well as other features of their reactions.