Bis(2,2,2-trifluoroethyl)bromophosphonoacetate, a Novel HWE Reagent for the Preparation of (E)-alpha-Bromoacrylates: A General and Stereoselective Method for the Synthesis of Trisubstituted Alkenes.
A novel reagent, methyl bis(2,2,2-trifluoroethoxy)bromophosphonoacetate (3a), was designed and prepared in order to efficiently synthesize (E)-alpha-bromoacrylates, which are useful precursors for various C-C bond formations. Honer-Wadsworth-Emmons (HWE) reaction of various aldehydes with 3a in the presence of t-BuOK and 18-C-6 gave the corresponding (E)-alpha-bromoacrylate derivatives with high stereoselectivity. Using the (E)-alpha-bromoacrylate as a key intermediate, a general stereoselective synthesis of trisubstituted alkenes via Pd-catalyzed cross-coupling was developed.
Tago
K
Exploratory Chemistry Research Laboratories, Sankyo Co., Ltd., 2-58, Hiromachi, 1-chome Shinagawa-ku, Tokyo, 140-8710 Japan.
Kogen
H