Phosphite-mediated conversion of benzaldehydes into stilbenes via umpolung through a dioxaphospholane intermediate

AbstractThe phosphite-mediated coupling of two benzaldehydes into 2,2,2-triethoxy-1,3,2-dioxaphospholanes was investigated using 13C NMR spectroscopy and was found to be very sensitive to the nature of the ortho/para substituents, and promoted by electron-withdrawing groups (EWGs). Stilbene-extended tetrathiafulvalenes were prepared by heating the intermediate dioxaphospholane, containing aldehyde substituents at para positions and ethynyl groups at ortho/meta positions, with 1,3-dithiol-2-thiones in P(OEt)3. While EWGs promoted dioxaphospholane formation, electron-donating groups (EDGs), generated by conversion of the aldehydes into dithiafulvenes, promoted subsequent conversion into an alkene