A Highly Stereoselective Synthesis of (E)-α-Bromoacrylates

Novel reagent, methyl bis(2,2,2-trifluoroethoxy)bromophosphonoacetate (5a), was designed and prepared in order to efficiently synthesize (E)-α-bromoacrylates 7, from which widely useful precursors for various C–C bond formations were prepared. Horner–Wadsworth–Emmons (HWE) reaction of various aldehydes with 5a in the presence of t-BuOK and 18-C-6 gave corresponding (E)-α-bromoacrylate derivatives with high stereoselectivity and excellent yield. Using the product (E)-α-bromoacrylate 7s as a key intermediate, we succeeded in developing the most effective route of plaunotol synthesis via Suzuki cross-coupling.