49769-76-8Relevant articles and documents
The copper-catalyzed selective monoalkylation of active methylene compounds with alkylsilyl peroxides
Lv, Jiamin,Xu, Weiping,Lu, Hanbin,Kato, Terumasa,Liu, Yan,Maruoka, Keiji
supporting information, p. 2658 - 2662 (2021/04/07)
A novel method for a mild copper-catalyzed selective monoalkylation of active methylene compounds with various alkylsilyl peroxides has been developed. The reaction has a broad substrate scope and our mechanistic studies suggest the participation of radical species in this alkylation reaction.
On the most powerful chemical traps for bis(methoxycarbonyl)carbene (=2-methoxy-1-(methoxycarbonyl)-2-oxoethylidene)
Shevchenko, Vladimir V.,Zhegalova, Natalya G.,Borzenko, Andey O.,Nikolaev, Valerij A.
experimental part, p. 501 - 509 (2009/02/07)
The efficiency and validity of different chemical substrates for trapping bis(methoxycarbonyl)carbene (=2-methoxy-1-(methoxycarbonyl)-2-oxoethylidene; 1) is dependent on the conditions of carbene generation. On conventional photolysis of dimethyldiazomalonate (=2-diazopropanedioic acid dimethyl ester; 2) by long-wave UV light (through a Pyrex filter, λ > 290 nm), the most powerful trap for carbene 1 in the series of substrates Me2S, MeOH, cyclohexane, and pyridine is Me2S (with an efficiency ratio of ca. 6 :4 : 2 : 1, resp.). When short-wave decomposition of diazomalonate 2 is employed (through a quartz filter, λ > 210 nm), more reliable and useful chemical traps for bis(methoxycarbonyl)carbene (1) are pyridine and cyclohexane, whose adducts with 1 are rather stable under short-wave-irradiation conditions. Application of alcohols for the trapping of 1 proves to be preferential when simultaneous monitoring of carbene and oxoketene formation during photolysis is necessary.
1,3-Stereoinduction in radical reactions: Radical additions to dialkyl 2-alkyl-4-methyleneglutarates
Hayen,Koch,Saak,Haase,Metzger
, p. 12458 - 12468 (2007/10/03)
Tin hydride-mediated radical additions to a series of α-methylene-glutarates 1, furnishing 2;4-dialkyl-substituted glutarates 3 are reported. The diastereoselectivity of hydrogen transfer to the intermediate adduct radicals 2, possessing a stereogenic center in γ-position, was disappointing in the temperature range of -78 to 80 °C. However, the reactions proved to be able to proceed with excellent 1,3-diastereoselectivities under chelation-controlled conditions, depending on the steric impacts of 2- and 4-alkyl substituents as well as on the ester-alkyl moiety and choice of Lewis acid. Using MgBr2·OEt2 as additive, syn-selectivities of 98:2 were achieved upon initial tert-butyl radical addition at -78 °C. High anti-diastereoselectivities were observed in the MgBr2·OEt2-controlled pathway at 70 °C when smaller alkyl radicals such as cyclohexyl, ethyl, and methyl were applied. Interesting and uncommon temperature dependences were observed in the temperature range of -78 to 100 °C, revealing strong entropic effects in the transition states. A model that accounts for the opposed stereochemical outcomes under chelation-controlled conditions is presented.
