Chemodivergence in alkene/allene cycloetherification of enallenols: Iron versus noble metal catalysis

A method was proposed for chemo-differentiation between an alkene and an allene moiety using iron- or precious-metal catalysis. Chemodivergence in alkene and allene were also reported by cycloetherification of enallenols. It was observed that racemic enallenols were prepared from the 4-oxoazetidine-2- carbaldehyde through regio-controlled indium-mediated Barbier carbonyl-allenylation reactions. Prenylation and allenylation process were used to prepare an optically active non-β-lactam precursors from (R)-2,3-O-isopropylideneglyceraldehyde. The effects of different metal catalysis in the chemoselectivity of the hydroalkoxylation reaction were also observed during the study. The Lewis-acid catalyzed cyclization of unsaturated alcohol was examined in the presence of different metallic chlorides.