N-oxides, N-imides, and N-ylides of five-membered heterocycles. Part 5. Reactions of 2,4,5-triphenyl-3H-pyrrol-3-one 1-oxide

2,4,5-Triphenyl-3H-pyrrol-3-one 1-oxide (1) undergoes a variety of cycloaddition reactions across the nitrone system. Adducts with alkene dipolarophiles are, in the main, stable, but other adducts rearrange to give pyridones, pyrimidones, or oxazinones. The adducts with dimethyl acetylenedicarboxylate and with dimethyl maleate undergo an unusual decarboxylative rearrangement. Complex metal hydrides reduce the title compound to the 1-hydroxypyrrole, whereas catalytic reduction or electron transfer gives the 3-hydroxy-isomer. Reactions with hydroxylamine and related compounds give derivatives of 5-benzoyl-3,4-diphenylisoxazole.