Dearomative (4 + 3) Cycloaddition Reactions of 3-Alkenylindoles and 3-Alkenylpyrroles to Afford Cyclohepta[<i>b</i>]indoles and Cyclohepta[<i>b</i>]pyrroles
Ferdinand Taenzler, Jiasu Xu, Sudhakar Athe, Viresh H. Rawal
Abstract
The dearomative (4 + 3) cycloaddition reactions of 3-alkenylindoles with in situ-generated oxyallyl cations furnish cyclohepta[b]indoles, functionality-rich frameworks found in many bioactive compounds, including all pentacyclic ambiguine alkaloids. The analogous reactions between oxyallyl cations and 3-alkenylpyrroles afford cyclohepta[b]pyrroles. The cycloadducts are generally formed in good to high yields and diastereoselectivities and can be readily transformed into useful derivatives. Additionally, we report preliminary investigations into the enantioselective catalysis of the dearomative (4 + 3) cycloaddition using imidodiphosphorimidate catalysts.
Topics & Concepts
CycloadditionChemistryCatalysisEnantioselective synthesisCombinatorial chemistryMedicinal chemistryOrganic chemistryStereochemistryAsymmetric Synthesis and CatalysisSynthesis and Characterization of PyrrolesOxidative Organic Chemistry Reactions