57865-37-9Relevant articles and documents
Hydrocarbonylation of Enol Esters Catalyzed by a Palladium(II) Complex
Kudo, Kiyoshi,Oida, Yuji,Mitsuhashi, Koichi,Mori, Sadayuki,Komatsu, Koichi,Sugita, Nobuyuki
, p. 1337 - 1345 (2007/10/03)
The palladium(II)-catalyzed carbonylation of various enol esters in the presence of methanol under pressurized carbon monoxide was investigated. As typical results, the carbonylation of isopropenyl acetate afforded a cyclocarbonylation product, 2-methoxy-2,5,5-trimethyl-1,3-dioxolan-4-one, in 46% yield under carbon monoxide of 150 atm at 100 °C, whereas vinyl acetate selectively gave an α-hydroesterification product, methyl 2-acetoxypropionate, in 56% yield under 250 atm at 100 °C. On the contrary, the reaction of 3,3-dimethyl-1-buten-2-yl acetate gave exclusively a β-hydroesterification product, methyl 3-acetoxy-4,4-dimethylpentanoate, in 64% yield. The yields of these products show a maximum as a function of the base/palladium ratio and of the carbon monoxide pressure. The effects of the reaction variables, such as the MeOH/substrate ratio, the structure of the base, the base/Pd ratio, the CO pressure, and the reaction temperature, were examined for optimizing the process. The mechanisms for the unique cyclocarbonylation and highly regioselective hydrocarbonylation of enol esters involving hydridopalladium(II) intermediate are discussed.
Competing, kc, Borderline, ks, and Carbonyl Addition Processes in Solvolyses of α-Keto Mesylates and Triflates. α-Keto Cations. 5
Creary, Xavier
, p. 5568 - 5577 (2007/10/02)
Solvolysis studies on tertiary α-keto mesylates show quite varying responses in rate to solvent ionizing power.The m values are 1.01 for 2-benzoyl-2-adamantyl mesylate (12), 0.66 for the mesylate derivative of 2-hydroxy-2,4,4-trimethyl-3-pentanone (4), and 0.63 for the mesylate derivative of 2-hydroxy-2-methylpropiophenone (3).The mesylate derivative of methyl α-hydroxyisobutyrate (5) does not correlate well with YOTs values, but instead it gives behavior that parallels that of isopropyl tosylate.Mesylates 3-5 solvolyze giving varying ratios of elimination and substitution products at rates comparable to that of isopropyl mesylate. β-d6 isotope effects for 3 and 4 range from 1.69 to 2.08 and are consistent with the intermediacy of α-keto cations. β-Deuterium isotope effects for 5 are quite variable (1.40-2.52) and parallel the amount of elimination product formed (22-94percent).This is consistent with the intermediacy of a reversibly formed ion-pair intermediate which can suffer proton loss.However, the SN2 (intermediate) mechanism remains a possibility in solvolyses of 5.Mesylate 3 solvolyzed in trifluoroethanol with added triethylamine to give an alkoxyoxirane.With small amounts of added 2,6-lutidine the 1,2-elimination product was major , while with added methanesulfonic acid the rearranged trifluoroethyl ester of dimethylphenyl acetic acid was major.These variable products were interpreted in terms of competing carbonyl addition processes and processes involving the α-keto cation.Secondary triflates derived from α-hydroxypropiophenone, 2,2-dimethyl-4-hydroxy-3-pentanone, and ethyl lactate solvolyzed giving the simple substitution product.Rates parallel solvent nucleophilicity and suggest a ks process involving negligible cationic character at the carbon α to the carbonyl group. kΔ processes are also not involved in solvolyses of these secondary triflates.
