A nucleophilic addition/ring-contractive rearrangement of α-bromo N-alkoxylactams with organometallic reagents was developed, providing an efficient access to α-acylpyrrolidines incorporating various C­(sp 2) units such as aryl, heteroaryl, and alkenyl groups. The sequential reaction proceeds through a five-membered chelate formation using nucleophilic addition followed by ring contraction via the formation of N,O-hemiaminal with good yields and a broad substrate scope. Moreover, a preliminary result with the use of the chiral N-alkoxylactam for the diastereoselective reaction is described.