Friedel-crafts reactions of bis(trimethylsilyl)polyynes with acyl chlorides; a useful route to terminal-alkynyl ketones

Article abstract of DOI:10.1016/S0022-328X(00)89260-8

Bis(trimethylsilyl)acetylenes, Me₃Si(CC)_nSiMe₃, react with acyl chloride-aluminium chloride complexes, XC₆H₄ COCl·AlCl₃ in methylene chloride at 0-20° to form the corresponding ketones XC₆H₄CO(CC)_nSiMe₃ in excellent (n = 1) or moderate (n = 2, 4) yield. Treatment of the products with aqueous methanolic borax results in virtually quantitative liberation of the terminal alkynyl ketones XC₆H₄CO(CC)_nH. The method provides the first practical route to the ketotetraynes (n = 4) and usefully supplements existing oxidative methods for keto-monoyne and -diyne synthesis. The oxalyl chloride-aluminium chloride complex reacts with Me₃SiCCSiMe₃ to give the novel silyl-substituted heterocycle (I): {A figure is presented}.