Ruthenium-Catalyzed Hydrohydroxyalkylation of Acrylates with Diols and α-Hydroxycarbonyl Compounds To Form Spiro- and α-Methylene-γ-butyrolactones

Abstract

Under the conditions of ruthenium(0) catalyzed hydrohydroxyalkylation, vicinal diols 1a–1l and methyl acrylate 2a are converted to the corresponding lactones 3a–3l in good to excellent yield. The reaction of methyl acrylate 2a with hydrobenzoin 1f, benzoin didehydro-1f, and benzil tetradehydro-1f form the same lactone 3f product, demonstrating that this process may be deployed in a redox level-independent manner. A variety of substituted acrylic esters 2a–2h participate in spirolactone formation, as illustrated in the conversion of N-benzyl-3-hydroxyoxindole 1o to cycloadducts 4a–4h. Hydrohydroxyalkylation of hydroxyl-substituted methacrylate 2i with diols 1b, 1f, 1j and 1l forms α-exo-methylene-γ-butyrolactones 5b, 5f, 5j and 5l in moderate to good yield. A catalytic cycle involving 1,2-dicarbonyl-acrylate oxidative coupling to form oxaruthenacyclic intermediates is postulated. A catalytically competent mononuclear ruthenium(II) complex was characterized by single crystal X-ray diffraction. The influence of electronic effects on regioselectivity in reactions of nonsymmetric diols were probed using para-substituted 1-phenyl-1,2-propanediols 1g, 1m and 1n and density functional theory (DFT) calculations.

Ruthenium-Catalyzed Transfer Hydrogenation for C–C Bond Formation: Hydrohydroxyalkylation and Hydroaminoalkylation via Reactant Redox Pairs

“…Using a ruthenium(0) catalyst, diols react with acrylates to form spiro-γ-butyrolactones (Scheme 14). 81 Ethyl 2-(hydroxymethyl)acrylate reacts with diols by way of transient oxaruthenacycles that engage in E1cB elimination to furnish α-methylene-spiro-γ-butyrolactones. 81 As illustrated in couplings with 3-hydroxy-2-oxindoles, β-substituted acrylic esters provides spiro-γ-butyrolactones as single diastereomers.…”

“…81 Ethyl 2-(hydroxymethyl)acrylate reacts with diols by way of transient oxaruthenacycles that engage in E1cB elimination to furnish α-methylene-spiro-γ-butyrolactones. 81 As illustrated in couplings with 3-hydroxy-2-oxindoles, β-substituted acrylic esters provides spiro-γ-butyrolactones as single diastereomers. 81 Remarkably, the cycloadditions may be conducted in oxidative, redox-neutral or reductive modes using diols, ketols or diones, respectively, as reactants.…”

“…81 As illustrated in couplings with 3-hydroxy-2-oxindoles, β-substituted acrylic esters provides spiro-γ-butyrolactones as single diastereomers. 81 Remarkably, the cycloadditions may be conducted in oxidative, redox-neutral or reductive modes using diols, ketols or diones, respectively, as reactants. To illustrate, ethyl acrylate reacts with hydrobenzoin, benzoin or benzil to form an identical γ-lactone.…”

A Metallacycle Fragmentation Strategy for Vinyl Transfer from Enol Carboxylates to Secondary Alcohol C–H Bonds via Osmium- or Ruthenium-Catalyzed Transfer Hydrogenation

“…For non-symmetric diols 1c , 1d , 1f and 1g , the vinyl transfer proceeds in a completely regioselective manner and can be explained on the basis of our prior density functional theory (DFT) calculations in related alkyne-diol C-C couplings. 13 The more highly substituted triphenyl acetate O -TPA- 2c reacts with aryl substituted diols 1c , 1d , 1f and 1g , delivering adducts 6a , 6b , 6d and 6e in up to 93% isolated yield. Adduct 6c was not formed presumably due to steric issues.…”

“…Related ruthenium(0) mediated carbonyl-alkene oxidative couplings find precedent in the work of Chatani and Murai 10 and our own studies. 9,13 The regioselectivity of oxidative coupling is likely driven by formation of a less hindered primary carbon-osmium bond. Reversible oxidative coupling, as demonstrated in a related system, 9d might correct errors in regioselectivity.…”