Excellent Chiral Introduction by Diene Iron-Tricarbonyl Moiety. II : A Formal Synthesis of (+)- and (-)-Frontalin Using a Diastereoselective 1, 2-Nucleophilic Addition of Organometallics into a (Z)-Dienone Fe(CO)₃ Complex

Abstract

A nucleophilic addition of alkyllithiums to the (Z)-dienone iron-tricarbonyl [Fe(CO)₃] complex (3) gave the (Z)-dienol complex (4) exclusively, while the reaction of 3 with alkylmagnesium bromide or trialkylaluminum provided the (E)-dienol complex (2) via the isomerization of 3 to the (E)-dienone complex (1). Application of this methodology was demonstrated in a formal synthesis of both (+)- and (-)-frontalin from the same chiral starting material, {(2S, 5S)-(2E, 4Z)-tricarbonyl[2-5-η-11-chloro-2, 4-undecadien-6-one]iron} (8).