Stoichiometric Carbon–Carbon Bond Forming Reaction of 1,3-Diene with 1,2-Diene in a Ruthenium(0) Complex

A stoichiometric reaction of Ru­(η4-cisoid-2,3-dimethyl-1,3-butadiene)­(η4-1,5-COD)­(NCMe) (1a) with ethyl 2,3-butadienoate produces rac-prone,supine-(1S,2R,4S,5R)-1-anti-4-anti-Ru­(η3:η3-1-ethoxycarbonyl-2-methylidene-4,5-dimethylhex-4-ene-1,6-diyl)­(η4-1,5-COD) (2aa) in 90% yield and in 52% isolated yield. The stereochemistry of this and the related products shows prior coordination of the 1,2-diene followed by the nucleophilic attack of the coordinated 1,3-diene, where the Ru(0) complex distinguishes two different orthogonal π planes and the prostereogenic face, depending on the steric congestion, regardless of their electronic properties.