Ruthenium-catalyzed Hydrative Dimerization of Allenes

Abstract

Hydrative dimerization and hydration of allenes proceeded in the presence of a ruthenium catalyst and a strong acid such as trifluoroacetic acid. γ,δ-Unsaturated ketones and methyl ketones were isolated in moderate combined yields. No isomeric compound (isomeric enone) was isolated.

Gold(I)-catalyzed hydration of allenes

“…Although a number of O–H nucleophiles undergo efficient transition metal-catalyzed intermolecular addition across the C=C bond of an allene,12,13 water is not among them. In a lone example, the Ru(II)-catalyzed reaction of monosubstituted allenes with water led to competetive hydrative dimerization and hydration initiated via attack of water at the internal allenyl carbon atom 14. Attack of water at the central carbon of the allene is also observed in the Brønsted acid-catalyzed hydration of allenes 15.…”

Alkynes as Allylmetal Equivalents in Redox-Triggered C–C Couplings to Primary Alcohols: (Z)-Homoallylic Alcohols via Ruthenium-Catalyzed Propargyl C–H Oxidative Addition

“…6). In each experiment, the product of ( Z )-allylation 4p was formed in small quantities along with a substantial amount of allene dimerization 16 (possibly [2+2] cycloadducts) 16b and hydrodimerization 17 products ( VII ) 2 , 18,19 which appear as a complex mixture of isomers as determined by HRMS and GC-MS analysis (see Supporting Information). Unreacted allene VII was not detected.…”

“…These data suggest one important feature of the present catalytic system is that the requisite allene does not accumulate, but is generated transiently in a pairwise fashion with the aldehyde. A low steady state concentration of allene is important to suppress ruthenium catalyzed allene dimerization, 16,18 hydrodimerization 17 or thermally promoted allene [2+2] cycloaddition, 19 to produce dimers that poison the catalyst.…”

Aromatic Osmacyclopropenefuran Bicycles and Their Relevance for the Metal‐Mediated Hydration of Functionalized Allenes

“…Saito et al. described the use of [Ru 3 (CO) 10 ] to promote the formation of methyl and γ,δ‐unsaturated ketones in the presence of trifluoroacetic acid, whereas Widenhoefer and co‐workers demonstrated the gold‐mediated generation of allylic alcohols …”