Multiple Stereocontrol Using Organometallic Complexes. Applications in Organic Synthesis and Consideration of Future Prospects

The addition of nucleophiles to dienemolybdenum and dienyliron cationic complexes proceeds stereospecifically trans to the metal. This has been utilized to effect stereocontrolled multiple functionalization of six- and seven-membered rings by a sequence of nucleophile addition, hydride abstraction, and second nucleophile addition. Applications of this protocol in the synthesis of macrolide antibiotic subunits is discussed. Stereocontrol from the metal is also obtained during alkylation of enolates generated on an organometallic complex. Recent progress in this area is presented. 1. Introduction 2. Stereocontrolled Multiple Functionalization of Six- and Seven-Membered Rings Via Nucleophile Addition to Dienyliron Complexes 2.1. Synthesis of the (+)-Prelog-Djerassi Lactone 2.2. Synthesis of a Tylosin Subunit 2.3. Preliminary Studies for FK-506 and Macbecin Synthesis (unpublished) 3. Preparation and Chemistry of Diene-Substituted Cycloheptadienyliron Complexes 4. Uses of Dienemolybdenum Complexes for Stereocontrolled Multiple Functionalization of Six- and Seven-Membered Rings 5. Asymmetric Synthesis: Chiral Recognition During Enolate Additions to Dienyliron and Dienemolybdenum Complexes 6. Alkylation of Enolates: Metal-Directed Stereocontrol 7. Conclusions