Iron-Catalyzed Prins–Peterson Reaction for the Direct Synthesis of Δ4‑2,7-Disubstituted Oxepenes

A direct iron­(III)-catalyzed Prins–Peterson reaction involving α-substituted γ-triphenylsilyl bis-homoallylic alcohols and aldehydes is described. Thus, cis-Δ4-2,7-disubstituted oxepenes were synthesized in a diastereoselective reaction using sustainable catalytic conditions (3–5 mol %). This highly productive process is the result of a cascade of three chemical events with the concomitant formation of a C–O bond, a C–C bond, and a Δ4 endocyclic double bond, through a Prins cyclization followed by a Peterson-type elimination. This tandem reaction is chemoselective vs the classical Prins cyclization.