Unexpected Facile Sequential Halolactamization−Hydroxylation of 2,3-Allenamides with CuX2 for the Efficient Synthesis of 4-Halo-5-hydroxypyrrol-2(5H)-ones

4-Halo-5-hydroxypyrrol-2(5H)-ones were synthesized from the efficient sequential halolactamization−hydroxylation reaction of 4-monosubstituted 2,3-allenamides with CuX2 (X = Br, Cl) in high yields. Halolactamization of fully substituted 2,3-dienamide (1f) afforded 4-halo-pyrrol-2(5H)-ones.