Unexpected facile sequential halolactamization-hydroxylation of 2, 3-allenamides with CuX(2) for the efficient synthesis of 4-halo-5-hydroxypyrrol-2(5H)-ones

[reaction: see text] 4-Halo-5-hydroxypyrrol-2(5H)-ones were synthesized from the efficient sequential halolactamization-hydroxylation reaction of 4-monosubstituted 2,3-allenamides with CuX(2) (X = Br, Cl) in high yields. Halolactamization of fully substituted 2,3-dienamide (1f) afforded 4-halo-pyrrol-2(5H)-ones.