Stereoselective synthesis of chiral terminal (E)-1,3-enynes derived from the aldehydes (1R)-(-)-myrtenal and (S)-(-)-perillaldehyde using the alkynyl-phosphonio complex [Ru{C CCH2(PPh3)} (eta(5)-C9H7)(PPh3)(2)][PF6] as synthon

Treatment of alkynyl-phosphonio complex [Ru {C drop CCH2(PPh3)}(eta (5)-C9H 7)(PPh3)(2)][PF6] (1) with Li " Bu gives the ylide-alkynyl derivative [Ru{C drop CC(H)=PPh3} (eta (5)-C9H7)(PPh3)(2)] (2), which reacts in situ with t he optically active aldehydes(1R)-(-)-myrtenal and (S)-( -)-perillaldehyde via a Wittig process to afford sigma -alkynyl complexes [Ru {C drop CC(H)=C (H)C9H13}(eta (5)-C9H7)(PPh3)(2)] 3 and 7 respectively. Whereas compound 3 has been obtained stereoselectively as the pure E stereoisomer, complex 7 h as been synthesized as a mixture of the corresponding E and Z isomers (ca. 4.1 ratio). Protonation of 3 and 7 with HBF4. Et2O yields the cationic alke nyl-vinylidene derivatives (E)-[Ru {=C dropC(H)C(H)=C(H)C9H13}(eta (5)-C9H7 )(PPh3)(2)][BF4] (4, 8), which react with acetonitrile at reflux to afford the nitrile complex [Ru(N drop CMe)(eta (5)-C9H7)(PPh3)(2)][BF4] (6), and t he corresponding terminal 1,3-enynes (E)-HC drop CC(H)=C(H)C9H13 5 and 9 re spectively. (C) 2001 Elsevier Science B.V. All rights reserved.