title: Direct synthesis of Z-alkenyl halides through catalytic cross-metathesis.
abstract: Olefin metathesis has had a large impact on modern organic chemistry, but important shortcomings remain: for example, the lack of efficient processes that can be used to generate acyclic alkenyl halides. Halo-substituted ruthenium carbene complexes decompose rapidly or deliver low activity and/or minimal stereoselectivity, and our understanding of the corresponding high-oxidation-state systems is limited. Here we show that previously unknown halo-substituted molybdenum alkylidene species are exceptionally reactive and are able to participate in high-yielding olefin metathesis reactions that afford acyclic 1,2-disubstituted Z-alkenyl halides. Transformations are promoted by small amounts of a catalyst that is generated in situ and used with unpurified, commercially available and easy-to-handle liquid 1,2-dihaloethene reagents, and proceed to high conversion at ambient temperature within four hours. We obtain many alkenyl chlorides, bromides and fluorides in up to 91 per cent yield and complete Z selectivity. This method can be used to synthesize biologically active compounds readily and to perform site- and stereoselective fluorination of complex organic molecules.
authors.affiliation: Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA.
authors.forename: Ming Joo
authors.initials: MJ
authors.lastname: Koh
authors.affiliation: Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA.
authors.forename: Thach T
authors.initials: TT
authors.lastname: Nguyen
authors.affiliation: Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA.
authors.forename: Hanmo
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Richard R
authors.initials: RR
authors.lastname: Schrock
authors.affiliation: Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA.
authors.forename: Amir H
authors.initials: AH
authors.lastname: Hoveyda
mesh_terms: D000475:Alkenes / Q000138:chemical synthesis / Q000737:chemistry*; D001688:Biological Products / Q000138:chemical synthesis / Q000737:chemistry; D001965:Bromides / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D002712:Chlorides / Q000138:chemical synthesis* / Q000737:chemistry; D005459:Fluorides / Q000138:chemical synthesis* / Q000737:chemistry; D054879:Halogenation; D008982:Molybdenum / Q000737:chemistry
chemical_list: D000475:Alkenes; D001688:Biological Products; D001965:Bromides; D002712:Chlorides; D008982:Molybdenum; D005459:Fluorides