Straightforward Synthesis of a Vicinal Double‐Bridgehead Iodo Trimethylsilyl Octacycle: Unprecedented Lack of Reactivity of the Silyl Group in the Presence of Fluoride Anions

Abstract

A convenient synthesis of an octacyclic compound containing an iodo and a trimethylsilyl group in vicinal double‐bridgehead positions, as a possible precursor of a pyramidalized alkene, is described. The key step of the synthesis consists of a double nucleophilic substitution of two neopentyl‐type iodides by cyclopentadienide anions followed by two intramolecular Diels–Alder cycloadditions. All attempts to generate the expected pyramidalized alkene from the above precursor on reaction with different sources of fluoride failed. This octacyclic compound, which contains two disubstituted C=C bonds, underwent a chemo‐ and stereoselective Pd0‐catalyzed co‐cyclotrimerization with dimethyl acetylenedicarboxylate to give a nonacyclic cyclohexadiene derivative that can be aromatized upon reaction with CsF or transformed into a related fluoride upon reaction with AgF.