Ruthenium‐Catalyzed Propargylation of Aromatic Compounds with Propargylic Alcohols

Abstract Reactions of propargylic alcohols bearing a terminal alkyne moiety with aromatic compounds in the presence of a catalytic amount of thiolate‐bridged diruthenium complexes give the corresponding propargylated aromatic compounds in high yields with complete selectivity. Intramolecular reactions of propargylic alcohols bearing an aromatic moiety proceed smoothly to afford the cyclized products in high yields with complete selectivity. The stoichiometric reaction of the ruthenium–allenylidene complex [Cp*RuCl(μ 2 ‐SMe) 2 RuCp*(=C=C=CHPh)]BF 4 (Cp* = η 5 ‐C 5 Me 5 ) with 10 equiv. 2‐methylfuran results in the formation of 2‐methyl‐5‐(1‐phenyl‐2‐propynyl)furan in 34 % yield, indicating that these catalytic reactions proceed via ruthenium–allenylidene intermediates. The reaction is considered to be an electrophilic substitution of aromatic compounds by the ruthenium‐stabilized propargyl cation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)