Synthetic Studies for the 1,3-Iterative Organoiron Approach to the Synthesis of Siculinine: Efficient Arylation Using a Diarylcuprate Reagent

Disubstituted (cyclohexadienyl) iron(1+) complex 2b is prepared by an improved route that starts from 1,2-dimethoxycyclohexa-1,4-diene 3. In five steps, the synthesis of 2b is achieved by complexation with Fe(CO)(5), hydride abstraction, hydrolysis, addition of EtO2CCH2ZrBr, and reaction with HBF4. In the presence of dimethyl sulfide, the reaction of 2b with 2-[CH2N(CH2CH=CH2)(2)]-functionalized diarylcuprate reagent 7 gave the 5 alpha-arylcyclohexadiene complex 1b in 88% yield. A DFT study compared diarylzinc and diarylcuprate reagents containing chelating CH2NMe2 substituents.