Diastereoselective Attack on Chiral-at-Metal Ruthenium Allenylidene Complexes To Give Alkynyl Complexes

Abstract

New chiral ruthenium(II) allenylidene complexes were synthesized, and their reactivity with nucleophiles to give alkynyl complexes was investigated. The new allenylidene complex (RRu,Rax)-[Ru(Ind)(PPh3)(6){═C═C═C(t-Bu)(2-naphthyl)}]+PF6– was synthesized from the chloro precursor complex (RRu,Rax)-[RuCl(Ind)(PPh3)(6)] and the racemic propargylic alcohol HC≡CC(OH)(t-Bu)(2-naphthyl) and obtained in 96% yield, where (Rax)-6 is a chiral phosphoramidite and Ind an anionic indenyl ligand. The precursor and the allenylidene complex are chiral-at-metal, and the chiral information is completely transferred from the chloro precursor to the product allenylidene complex, both of which show the same absolute configuration, as demonstrated by X-ray diffraction. Together with the known allenylidene complex (RRu,Rax)-[Ru(Ind)(PPh3)(6)(═C═C═CPh2)]+PF6–, the attack of n-BuLi, MeLi, LiC≡CPh, and lithium 1-phenylethenolate nucleophiles on the allenylidene chain of (RRu,Rax)-[Ru(Ind)(PPh3)(6){═C═C═C(t-Bu)(2-naphthyl)}]+PF6– wa...