- Asymmetric synthesis of highly substituted β-lactones by nucleophile-catalyzed [2+2] cycloadditions of disubstituted ketenes with aldehydes
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α,α-Disubstituted β-lactones can be obtained by the cycloaddition of the corresponding ketenes with aldehydes (see scheme). For the first time, a chiral PPY derivative, 1, serves as an efficient catalyst for the asymmetric synthesis of β-lactones (PPY = 4-pyrrolidin-1-ylpyridine). To date, this is the only catalyst that is effective for enantioselective cycloadditions of disubstituted ketenes with aldehydes. (Chemical equation presented).
- Wilson, Jonathan E.,Fu, Gregory C.
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- Catalytic asymmetric heterodimerization of ketenes
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In this Communication we describe an unprecedented catalytic asymmetric heterodimerization of ketenes of wide substrate scope. The alkaloid-catalyzed method provides access to ketene heterodimer β-lactones and allows even two different monosubstituted ketenes to be cross-dimerized, with excellent enantioselectivity (17 examples with ≥90% ee) and excellent heterodimer regioselectivity observed in all cases.
- Ibrahim, Ahmad A.,Nalla, Divya,Van Raaphorst, Maxwell,Kerrigan, Nessan J.
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supporting information; experimental part
p. 2942 - 2945
(2012/04/10)
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- A Novel Series of N-(1-Aminoalkylidene)carboximidamides as Potential Hypoglycemic Agents
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Nitrogen heterocyclic carboximidamides, such as linogliride, 1a, have been shown to possess significant hypoglycemic activity and have shown clinical efficacy as potential antidiabetic agents.We evaluated the biological significance of the heterocyclic ring A of general structure 1, which has always been maintained in this class of compounds, by preparing acyclic compounds of general structure 2.Preliminary in vivo biological testing, i.e., the glucose tolerance test in rats, indicates that a number of the specific acyclic carboximidamides prepared, 6a-6kk, possessed significant hypoglycemic activity often comparable to, and in some cases better than, the activity noted for our model compound, 1a.These results suggest that the heterocyclic ring A of 1 is not essential for hypoglycemic activity for this class of compounds.
- Breslin, Henry J.,Kukla, Michael J.,Tuman, Robert W.,Rebarchak, Mary C.,Bowden, Charles R.
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p. 1597 - 1603
(2007/10/02)
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- Silicon Hydrides and Molybdenum(O) Catalyst: A Novel Approach for Conjugate Reduction of α,β-Unsaturated Carbonyl Compounds
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A novel reducing system comprised of phenylsilane and catalytic amounts of Mo(CO)6 in refluxing THF efficiently effects conjugate reduction of Michael acceptors, including α,β-unsaturated ketones, carboxylic acids, carboxylic esters, amides, and nitriles.The process involves molybdenum-catalyzed hydrosilation, followed by hydrolysis of the intermediate silyl enol ether.Hydride is regioselectively transferred from the hydridosilane to the β-carbon of the substrate, and a proton from water is incorporated into the α-carbon.
- Keinan, Ehud,Perez, Daniel
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p. 2576 - 2580
(2007/10/02)
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- Ruthenium Tetroxide Oxidation of N-Acylated Alkylamines: A New General Synthesis of Imides
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Oxidation of various N-acylalkylamines with ruthenium tetroxide (RuO4) was systematically investigated.N-acylalkylamines having an electron-donating group at the α- or β-position with respect to amide nitrogen or an electron-donating alkyl function in the acyl group were smoothly oxidized to the corresponding imides in excellent yields.On the other hand, N-acylalkylamines having an electron-withdrawing group were not oxidized at all, and most of the starting material was recovered.It appears that the reactivity of N-acylalkylamines is closely correlated with the acidity of the carboxylic acid from which the N-acyl group is derived, and also with the electron density at the methylene moiety adjacent to the amide nitrogen atom.Keywords---oxidation; ruthenium tetroxide oxidation; imide synthesis; acyclic imide; amide; ruthenium tetroxide; substituent effect
- Tanaka, Ken-Ichi,Yoshifuji, Shigeyuki,Nitta, Yoshihiro
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p. 364 - 369
(2007/10/02)
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