Synthesis of 5-Substituted a,b-Unsaturated g-Lactams from N-Sulfinyl Azadienes by Iron-mediated Reaction Cascades and Palladiumcatalyzed Cyclocarbonylation Strategies

A new synthesis of 5-substituted a,b-unsaturated g-lactams is reported. b-[Cp(CO)2Fe]-Substituted N-sulfonyl1 and Nsulfinyl azadienes 1 react with Grignard reagents or organolithium compounds furnishing 5-substituted a,b-unsaturated g-lactams 3.2,3 These reaction cascades occur by initial attack of the organometallic reagent at the imine functionality followed by an intramolecular cyclocarbonylation step. In a number of cases non-N-protected lactams are obtained from N-sulfonyl azadienes besides the desired N-sulfonyl g -lactams 3. Moreover, chiral b-[Cp(CO)2Fe]-substituted N-sulfinyl azadienes 1 react with the organometallic reagents to furnish exclusively 5-substituted non-N-protected g - lactams 3.2,3