Ruthenium-Catalyzed Decarboxylative Allylation of Nonstabilized Ketone Enolates

Abstract

[reaction: see text] Bipyridyl(pentamethylcyclopentadienyl)ruthenium chloride is an efficient catalyst for the formal [3,3] rearrangement of allyl beta-ketoesters. The mechanism of the transformation involves formation of pi-allyl ruthenium intermediates, which are selectively attacked at the more substituted allyl terminus by freely diffusing enolates. Decarboxylation of beta-ketocarboxylates allows generation of enolates under extremely mild conditions.

Enantioselective CpRu‐Catalyzed Carroll Rearrangement – Ligand and Metal Source Importance

“…Generally, Cp*Ru-and CpRu-catalyzed allylation reactions are believed to proceed through the formation of Ru-π-allyl complexes with leaving group release, [5,6] and the decarboxylative addition of enolates is no exception. [7] In this latter case (Scheme 4), the oxidative addition of the metal complex to the substrate leads to the release of a keto acetate moiety, which upon decarboxylation, generates an "unstabilized" enolate. This nucleophilic www.eurjoc.orgenolate subsequently adds to the π-allyl complex to regenerate the catalytically active Ru complex and furnishes the γ,δ-unsaturated ketone.…”

“…In addition, the fact that the new C-C bonds in 2h to 2l and 3h to 3l (Scheme 6) resulted solely from the attack of the carbon previously bearing the carboxylate moiety is compatible with the formation of enolates whose regiochemistry is preserved throughout the catalytic cycle. [7] Scheme 6. Conservation of the enolate regiochemistry for 1k.…”

“…The linear regioisomer 3 was formed only in trace amounts. [7,8] The particularly mild reaction conditions (CH 2 Cl 2 , room temperature), in sharp contrast with those of thermal decarboxylative [3,3]-sigmatropic Carroll reactions (140-180°C), [9,10] were particularly interesting. The involvement of the metal moiety was key to the observed enhanced reactivity and augured well for the development of an enantioselective version of the reaction.…”

Metal‐Free SN2′ Decarboxylative Rearrangement of β‐Keto Esters

“…[14] However, these methods suffer from the need for two equivalents of base and requires an additional step to carry out the decarboxylation. Recently, decarboxylations of allyl β-keto carboxylates catalyzed by transition metals (Ru, [15] Pd [16] ) in the presence of chiral ligands have been successfully developed. Adsorption of β-keto esters on neutral alumina has also been used for the Carroll rearrangement of a precursor of zincophorin.…”

Ruthenium Catalyzed Selective Regio‐and‐Mono‐Allylation of Cyclic 1,3‐Diketones Using Allyl Alcohols as Substrates

“…[19g] There are now a number of Ru complexes capable of catalyzing allylation reactions [20][21][22][23][24][25][26] and Scheme 1 shows a selection of these.…”