Alkynyl halides and chalcogenides

This chapter summarizes the literature from 1995 through 2003 with emphasis on the modern synthetic approaches to alkynyl halides and chalcogenides. The preparation of alkynyl chlorides, bromides, and iodides via various elimination reactions or the reaction of terminal alkynes with electrophilic halogenating reagents is extensively reviewed. The most general and widely used approach to the synthetically important alkynyl bromides and iodides consists in the treatment of terminal alkynes or trimethysilylalkynes with the appropriate N-halosuccinimide in acetone in the presence of silver nitrate as a catalyst. The newest member of the family of alkynyl halides, alkynyliodonium salts, are best prepared by the ligand exchange reaction of stannylated alkynes with phenyl(cyano)iodonium triflate. Alkynyl ethers and thioethers are commonly synthesized by dehydrohalogenation of the appropriate haloalkenyl ethers or thioethers. The best synthetic procedures for the preparation of alkynyl selenides and tellurides employ the reaction of a metal alkynylide with elemental selenium or tellurium, followed by trapping of the intermediate lithium selenolate or tellurolate with alkyl halides or other appropriate electrophiles.