- The Co(I) induced methylmalonyl-succinyl rearrangement in a model for the coenzyme B12 dependent methylmalonyl-CoA mutase.
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The rearrangement of 2-bromomethyl-2-methylmonothiomalonates to succinyl derivatives was found to take place in quantitative yields in the presence of one molar equivalent of Co(I) generated by the reduction of heptamethyl Co(II)yrinate perchlorate with NaBH4 or electrochemically. The chiral thiomalonate gave racemic succinate.
- Sun, Fangping,Darbre, Tamis
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p. 3154 - 3159
(2007/10/03)
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- 175. Model studies for the coenzyme-B12-catalyzed methylmalonyl→succinyl rearrangement. The importance of hydrophobic peripheral associations
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The interaction between a vitamin B12 derivative containing a peripheral C18 alkyl chain (see 1a) and a (methyl)thiomalonate substrate bearing alkyl chains of various length at the thioester group (see 5) was investigated. A catalytic cycle was established for the methylmalonyl→succinyl rearrangement by using electrochemistry and photolysis (see Scheme 3). Increased yields of the succinate relative to the reduction product were obtained (2:3 ratio), when the reaction was run in MeOH/H2O, and when both the substrate and the catalyst had an octadecyl substituent capable of hydrophobic interactions.
- Darbre, Tamis,Keese, Reinhart,Siljegovic, Vuk,Wolleb-Gygi, Annemarie
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p. 2100 - 2113
(2007/10/03)
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- 30. On the Regioselectivity Control in the Palladium-Catalyzed Hydro-alkoxycarbonylation of α,β-Unsaturated Esters
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The regioselectivity of the hydro-alkoxycarbonylation of methyl acrylate, methacrylate, and crotonate catalyzed by complexes (L = phosphine ligands) can be largely controlled by variation of the ligands.PPh3 promotes preferential carbonylation a
- Consiglio, Giambattista,Nefkens, Sylvia C. A.,Pisano, Carmelina,Wenzinger, Fritz
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p. 323 - 325
(2007/10/02)
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- Carbonylation (hydroformylation and hydrocarbalkoxylation) and enantioselective carbonylation of some methacrylic acid derivatives
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The hydroformylation of methyl methacrylate (1) or t-butyl methacrylate (2) takes place with fair to good chemoselectivity, the regioselectivity depending on the catalyst precursor used.By contrast, methacrylonitrile (3), methacrylamide (4), and N-benzyl-methacrylamide (5) undergo hydroformylation followed by subsequent reactions.The formyl product formed is reduced to the corresponding 2-cyano-2-methylpropan-1-ol in the case of 3, and undergoes cyclization to 2-methyl-2,3-dehydrobutyrolactames for 4 and 5.Under conditions of hydrocarbalkoxylation in the presence of palladium catalysts, 4 gives 3-methylsuccinimide.In the enantioselective reactions, extents of asymmetric induction of about 20-50percent have been obtained.
- Consiglio, Giambattista,Kollar, Laszlo,Koelliker, Robert
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p. 375 - 383
(2007/10/02)
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- Process to produce silyl ketene acetals
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A process for the preparation of silyl ketene acetals of the formulae, from the reaction of a malonate compound with a triorganohalosilane in the presence of an alkali metal. The malonate compounds are dialkyl dialkylmalonates, bis(trialkylsilyl) dialkylmalonates, and dialkylmalonic acids. The triorganohalosilane is present in stoichiometric excess relative to the malonate compounds. Silyl ketene acetals are isolated and separated.
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