- Experimental and computational evidence on gold-catalyzed regioselective hydration of phthalimido-protected propargylamines: An entry to β-amino ketones
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The results of our investigations on the Au-catalyzed regioselective hydration reaction of both alkyl- A nd aryl-substituted N-propargyl phthalimides directed to the selective formation of the corresponding β-phthalimido ketones are described. Experimental data, in particular the observed regioselectivity, have been qualitatively supported by quantum-chemical calculations carried out on model systems in the framework of Density Functional Theory (DFT) followed by quantum theory of atoms in molecules (QTAIMS). Our results suggest that the electronic features of the initial adduct between the propargyl triple bond and the Au(i) catalyst, in particular the character of the gold-triple bond interaction, are essential for the observed regioselectivity. Other effects, such as the presence of the solvent and the formation of a H-bond between the water molecule and the phthalimido moiety, although apparently irrelevant for the regioselectivity, have proven to be kinetically and catalytically rather important. This journal is
- Arcadi, Antonio,Aschi, Massimiliano,Marsicano, Vincenzo,Michelet, Véronique
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p. 9438 - 9447
(2020/12/15)
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- Aldehyde-selective wacker-type oxidation of unbiased alkenes enabled by a nitrite co-catalyst
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Breaking the rules: Reversal of the high Markovnikov selectivity of Wacker-type oxidations was accomplished using a nitrite co-catalyst. Unbiased aliphatic alkenes can be oxidized with high yield and aldehyde selectivity, and several functional groups are tolerated. 18O-labeling experiments indicate that the aldehydic O atom is derived from the nitrite salt. Copyright
- Wickens, Zachary K.,Morandi, Bill,Grubbs, Robert H.
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supporting information
p. 11257 - 11260
(2013/11/06)
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- Catalyst-controlled Wacker-type oxidation of protected allylic amines
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On the contrary: Utilizing the [Pd-(quinox)]-TBHP catalyst system, protected allylic amines were oxidized with high selectivity for the methyl ketone product. This is contrary to the results obtained by the substrate-controlled Tsuji-Wacker oxidation, which highlights the catalyst-controlled system presented here (see scheme). A variety of N-pro-tecting groups undergo selective oxidation with high ketone selectivity. TBHP = tert-butylhydroperoxide.
- Michel, Brian W.,McCombs, Jessica R.,Winkler, Andrea,Sigman, Matthew S.
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supporting information; experimental part
p. 7312 - 7315
(2010/11/05)
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- Exploratory studies probing the intermediacy of azomethine ylides in the photochemistry of N-phthaloyl derivatives of α-amino acids and β-amino alcohols
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Exploratory photochemical studies with N-phthaloyl derivatives of glutamic acid, aspartic acid, serine, threonine and analogous carboxylic acids and alcohols have been conducted to determine the generality of azomethine ylide forming decarboxylation and retro-aldol fragmentation reactions. Preferences in the competition between these excited state reaction pathways have been determined by studies with phthalimides which contain both α-amino acid and β-aminoethanol groups.
- Yoon, Ung Chan,Lee, Chan Woo,Oh, Sun Wha,Mariano, Patrick S.
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p. 11997 - 12008
(2007/10/03)
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- Photochemistry of N-phthaloyl derivatives of electron-donor-substituted amino acids
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The hydroxy substituted amino acids threonine and serine have been investigated concerning their photochemical behaviour when activated as N-phthaloyl substrates. The methyl esters 1a and 2a solely underwent cleavage of the central C-C single bond to give the glycine derivative 3 and an aldehyde fragment. C-unprotected threonine derivative 1b is converted into a series of products the composition of which depends on solvent polarity and on the electronic state. Three reaction modes were detected for the N-phthaloyl derivatives of the aryl substituted amino acids phenylalanine, tyrosine, and dihydroxyphenylalanine (DOPA): (A) decarboxylation (only for 12a), (B) β-fragmentation, and (C) ring enlargement reaction. Processes B and C are initiated by photo electron transfer (PET), as the solvent dependence revealed. The DOPA derivatives 14a and 14b are the most prominent examples due to their exclusive PET reactivity leading to type C products (18a,b) with high diastereoselectivity (90:10). PET results from the first excited singlet states of 12 and 13, whereas for compounds 14 the corresponding triplet states are involved. The correlation between photochemical reactivity and the fluorescence decay data for compounds 12a,b and 15 is discussed.
- Griesbeck,Henz,Hirt,Ptatschek,Engel,Loffler,Schneider
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p. 701 - 714
(2007/10/02)
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