Reactions of (η5-C5H5)(CO)2Fe-Substituted N-Sulfonyl Azadienes with C-Nucleophiles. A Route to 5-Substituted Dihydropyrrolones

A variety of cyclic β-[(η5-C5H5)(CO)2Fe]-substituted N-sulfonyl azadienes 4 were prepared: e.g., from the corresponding iron-substituted (Z)-enals and benzenesulfonamide. Reactions of these iron compounds with Grignard reagents or organolithiums gave 5-substituted α,β-unsaturated N-sulfonyl γ-lactams 5. In some cases the corresponding non-N-protected 5-substituted γ-lactams 6 were isolated as well. Key steps of these reaction cascades are the initial 1,2-addition to the imine moiety and the subsequent carbonylation step. The reaction of the chromene−iron complex 4e with (allyl)MgCl gave the (η3-allyl)iron−γ-lactam complex 8a with a ring-opened chromene framework. This complex was structurally characterized by X-ray analysis.