Reactions of (eta(5)-C5H5)(CO)(2)Fe-substituted N-sulfonyl azadienes with C-nucleophiles. A route to 5-substituted dihydropyrrolones

A variety of cyclic beta-[(eta(5)-C5H5)(CO)(2)Fe]-substituted N-sulfonyl az adienes 4 were pre pared: e.g., from the corresponding iron-substituted (Z) -enals and benzenesulfonamide. Reactions of these iron compounds with Grign ard reagents or organolithiums gave 5-substituted alpha,beta-unsaturated N- sulfonyl gamma-lactams 5. In some cases the corresponding non-N-protected 5 -substituted gamma-lactams 6 were isolated as well. Key steps of these reac tion cascades are the initial 1,2-addition to the imine moiety and the subs equent carbonylation step. The reaction of the chromene-iron complex 4e wit h (allyl)MgCl gave the (eta(3)-allyl)iron-gamma-lactam complex 8a with a ri ng-opened chromene framework. This complex was structurally characterized b y X-ray analysis.