ChemInform Abstract: A Mechanistic Dichotomy Leading to a Ruthenium-Catalyzed cis-Addition for Stereoselective Formation of (Z)-Vinyl Bromides

Either trans- or cis-haloalkylation is possible through a three-component coupling [Eq. (1)]. The cis-bromoruthenation of an alkyne by lithium bromide and [CpRu(CH(3)CN)(3)]PF(6), catalyzed by SnBr(4), gives (Z)-vinyl bromides with high chemoselectivity. The degree of control over the sterochemistry raises intriguing mechanistic questions as well as offering practical synthetic utility.