Synthesis of functionalized cyclic enamines from lithium alkylphenyl sulfones and N‐carbo‐tert‐butoxy lactams

Alkylphenyl sulfones 3 are appropriate synthons for the synthesis of 2‐phenylsulfonyl alkylidene pyrro‐lidine or piperidine derivatives 1 in good to moderate yields. The lithium alkyl sulfones 4 are first reacted with the desired protected lactams and then subjected to acidic methanolysis to afford the unusual enam‐ines 1a‐e . NMR studies (COSY ¹H‐¹H, COSY ¹H‐¹³C, NOE) showed the Z enamines to exist in a dynamic equilibrium with the corresponding imines 2 . The stereochemistry of the described compounds was confirmed by molecular calculations.