Ruthenium carboxylate complexes as easily prepared and efficient catalysts for the synthesis of β-oxopropyl esters

The easily prepared complex cis-[Ru(κ2-O2CMe)2(PPh3)2] is an effective catalyst for the addition of carboxylic acids to propargyl alcohols to afford β-oxopropyl esters. The reaction is tolerant to a range of functional groups on the propargyl alcohol and is effective in the case of the steroid ethisterone. An investigation into the ruthenium-containing products from the reaction involving benzoic acid revealed that rapid exchange between coordinated acetate and benzoate ligands occurs. The synthesis of crystallographically characterised cis-[Ru(κ2-O2CPh)2(PPh3)2] was developed. This benzoate-substituted complex was shown to react with HCCPh and HCCC(OH)PhH to give [Ru(κ2-O2CPh)(κ1-O2CPh)(CCPhH)(PPh3)2] and [Ru(κ2-O2CPh)(κ1-O2CPh)(CCC{OH}PhH)(PPh3)2] respectively. Reaction of cis-[Ru(κ2-O2CPh)2(PPh3)2] with CO affords [Ru(κ2-O2CPh)(κ1-O2CPh)(CO)(PPh3)2] or [Ru(κ2-O2CPh)2(CO)2(PPh3)2] depending on the conditions employed. Related carbonyl compounds are thought to be the ruthenium-containing products from the catalytic reactions and [Ru(κ2-O2CMe)(κ1-O2CMe)(CO)(PPh3)2] was also shown to be a competent catalyst.

The easily prepared ruthenium carboxylate complexes cis-[Ru(κ2-O2CR′)2(PPh3)2], (R′ = Me, Ph) are effective catalysts for the addition of carboxylic acids to propargyl alcohols to give β-oxopropyl esters.Figure optionsDownload as PowerPoint slideResearch highlights
► [Ru(κ2-OAc)2(PPh3)2] is an easily prepared and efficient catalyst for the addition of carboxylic acids to propargyl alcohols.
► Mechanistic and stoichiometric studies into the catalytic behaviour are reported.
► Facile exchange between free and coordinated carboxylate ligands may occur.
► [Ru(κ2-O2CPh)2(PPh3)2] may reaction with HCCPh and HCCC(OH)PhH to give vinylidene complexes.