A stereoselective synthesis of (E)-1-halo-6,6-dimethyl-2-hepten-4-yne: a key intermediate for terbinafine

A study of the stereoselective halogenation of 6,6-dimethyl-1-hepten-4-yn-3-ol (1) using a series of halogenating agents is described. Of the many agents investigated, boron trichloride is the most successful reagent for stereoselective halogenation (E:Z=9:1max). The resulting (E)-1-halo-6,6-dimethyl-2-hepten-4-yne (2), a key intermediate for terbinafine, an antifungal agent, is obtained in good yield and stereoselectivity. Two structurally related enyne alcohols have been studied likewise and shown similar versatility.