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)}(η5-C9H7)(PPh3)2][PF6] as synthon

Treatment of alkynyl–phosphonio complex [Ru{CCCH2(PPh3)}(η5-C9H7)(PPh3)2][PF6] (1) with LinBu gives the ylide–alkynyl derivative [Ru{CCC(H)PPh3}(η5-C9H7)(PPh3)2] (2), which reacts in situ with the optically active aldehydes (1R)-(−)-myrtenal and (S)-(−)-perillaldehyde via a Wittig process to afford σ-alkynyl complexes [Ru{CCC(H)C(H)C9H13}(η5-C9H7)(PPh3)2] 3 and 7 respectively. Whereas compound 3 has been obtained stereoselectively as the pure E stereoisomer, complex 7 has 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 alkenyl–vinylidene derivatives (E)-[Ru{CC(H)C(H)C(H)C9H13}(η5-C9H7)(PPh3)2][BF4] (4, 8), which react with acetonitrile at reflux to afford the nitrile complex [Ru(NCMe)(η5-C9H7)(PPh3)2][BF4] (6), and the corresponding terminal 1,3-enynes (E)-HCCC(H)C(H)C9H135 and 9 respectively.