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.