Iron-Mediated Synthesis of Heterocyclic Ring Systems and Applications in Alkaloid Chemistry

The reaction of tricarbonyliron-Complexed cyclohexadienylium cations with arylamines allows regio- and stereoselective formation of carbon-carbon and carbon-nitrogen bonds, and gives easy access to nitrogen heterocyclic ring systems. Electrophilic aromatic substitution and subsequent oxidative cyclization provides a convergent route to biologically active carbazole alkaloids. Cyclization by nucleophilic substitution of a leaving group in the side chain of the cyclohexadiene ring opens up a versatile synthesis of 3-aza- and 1-azaspiro[5.5]undecanes. 1. Introduction 2. Regio- and Stereoselective Electrophilic Substitutions of Arylamines by Iron-Complexed Cations 3. Iron-Mediated Oxidative Cyclizations to Oxygenated Carbazoles 4. Total Synthesis of the Carbazomycins 4.1. Synthesis of 4-Deoxycarbazomycin B via Iron-Mediated Arylamine Cyclization 4.2. Chemoselective Oxidations of Iron-Cyclohexadiene Complexes 4.3. Synthesis of 4-Deoxycarbazomycin B via Iron-Mediated Iminoquinone Cyclization 4.4. Total Syntheses of Carbazomycin A, Carbazomycin B, and Carbazomycinal 5. Total Synthesis of 1-Methoxycarbazole Alkaloids 6. Regio- and Stereoselective Reactions of Iron-Complexed 4b,8a-Dihydrocarbazol-3-ones 7. Diastereoselective Iron-Mediated Spiroannulations 7.1. Cyclization to 3-Azaspiro[5.5]undecanes 7.2. Cyclization to 1-Azaspiro]5.5]undecanes 7.3. Synthetic Approach to the Discorhabdin and Prianosin Alkaloids 8. Conclusion