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ABSTRACT: 2-Benzyl benzothiazoles and benzimidazoles are easily oxidized under air and basic conditions to give the corresponding ketones in good yields. The use of palladium acetate as a catalyst has little effect and even gives, in some cases, much lower yields.
Organic & Biomolecular Chemistry 03/2013; · 3.70 Impact Factor
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ABSTRACT: The Ugi reaction is one of the most famous multicomponent couplings, and its efficiency is still explained by the original mechanism suggested by Ugi in the 60s. This article aims to present a thorough theoretical study of this reaction. It describes how the imine is activated and how the new stereogenic center is formed. Our calculations strongly suggest alternatives to some commonly accepted features, such as the reversibility of the intermediate steps, and temper the nature of the driving force of the reaction.
The Journal of Organic Chemistry 02/2012; 77(3):1361-6. · 4.45 Impact Factor
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ABSTRACT: 4-Hydroxy and mercapto pyridines were successfully tested in Ugi-Smiles couplings. Such multicomponent reactions applied to quinoline derivatives afford a very convenient and short synthesis of antimalarial analogues.
Organic Letters 12/2011; 14(2):476-8. · 5.86 Impact Factor
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ABSTRACT: The effect of hydrogen bonds on the fate of nucleophilic aromatic substitutions (S(N)Ar) has been studied in silico using a density functional theory approach in the condensed phase. The importance of these hydrogen bonds can explain the "built-in solvation" model of Bunnett concerning intermolecular processes between halogenonitrobenzenes and amines. It is also demonstrated that it can explain experimental results for a multicomponent reaction (the Ugi-Smiles coupling), involving an intramolecular S(N)Ar (the Smiles rearrangement) as the key step of the process. Modeling reveals that when an intramolecular hydrogen bond is present, it lowers the activation barrier of this step and enables the multicomponent reaction to proceed.
Chemistry 11/2011; 17(52):14929-34. · 5.93 Impact Factor
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ABSTRACT: The Nef reaction between isocyanides and acyl chlorides is studied at the M06-2X/6-311+G(d,p) level of theory in toluene. After proving that the reaction follows a concerted mechanism instead of an addition-elimination path, we study the influences of the solvent, the isocyanide, the acyl moiety and the leaving group on the energy profile of the reaction. The calculated data can be rationalized with the pK(a) of the leaving group, or more generally with the population of the oxygen lone pairs of the acyl moiety.
The Journal of Physical Chemistry A 08/2011; 115(35):10106-12. · 2.95 Impact Factor
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ABSTRACT: Spiroindolines could be synthesized via a very convenient one-pot procedure combining a Ugi coupling and a new copper-catalyzed oxidative process at a peptidyl position. Due to the nature of the first step, this method offers a straightforward access to complex alkaloids with four points of molecular diversity.
Chemical Communications 06/2011; 47(28):8145-7. · 6.17 Impact Factor
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ABSTRACT: We present a novel protocol for the efficient synthesis of fused benzimidazolo piperazines starting from a four-component Ugi-Smiles reaction and a subsequent three-step cascade involving an acid-catalyzed cyclization, an intramolecular reductive cyclization, and an oxidation.
The Journal of Organic Chemistry 06/2011; 76(11):4728-33. · 4.45 Impact Factor
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Annalen der Chemie und Pharmacie 05/2011; 2011(17):3117 - 3121. · 3.10 Impact Factor
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ABSTRACT: Furans may be ring opened via pallado-catalyzed reactions leading to α,β-unsaturated aldehydes and ketones tethered to indole and isoquinoline moieties. Besides their synthetic interest, these fragmentations bring interesting elements into the discussion around the reaction mechanisms involved in palladium C-H activations of electron-rich heterocycles.
Chemical Communications 02/2011; 47(6):1887-9. · 6.17 Impact Factor
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ABSTRACT: A short sequential synthesis of pyrrolidino- pyridines and pyrimidines illustrates the potential of combining Ugi-Smiles couplings with radical tin-free processes.
Molecules 01/2011; 16(11):9261-73. · 2.39 Impact Factor
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ABSTRACT: Herein, we present a new route to highly substituted pyrrolo[2,3-d]pyrimidines featuring a Ugi-Smiles/Sonogashira cascade followed by an efficient base-catalyzed intramolecular cyclization. When formaldehyde is chosen as input in the Ugi-Smiles step, aromatic fused systems are eventually obtained through the isomerization of an exo-alkylidene intermediate.
The Journal of Organic Chemistry 08/2010; 75(15):5343-6. · 4.45 Impact Factor
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ABSTRACT: To bypass the failure of radical cyclization involving a xanthate transfer on alkynes, a new reductive cyclization strategy has been completed with the use of a stoichiometric amount of dilauroyl peroxide in isopropanol. When the starting xanthates are prepared via a Ugi 4-component reaction with propargylamine, exomethylene lactams are formed in good yields.
Chemical Communications 04/2010; 46(14):2489-91. · 6.17 Impact Factor
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ABSTRACT: The scope of the Ugi reaction has been extended by the use of phenols as carboxylic acid surrogates to afford N-aryl carboxamides. A Smiles rearrangement occurs as the last step of the mechanism instead of the classical final Mumm process. Various parameters concerning the nature of these inputs have been studied: the use of heteroaromatic derivatives, the substitution of the hydroxyl moiety by a thio entity (to afford functionalized thioamides), as well as the influence of the nature and position of substituents on the phenol. A three-component version (Passerini-Smiles) of this coupling has been developed as well. Following these couplings, various post-condensation transformations have been performed to reach more complex heteroaromatic fused systems. The easy functionalizations of phenols offer many opportunities for cyclization strategies: the reduction of the nitro group allows the formation of o-phenylenediamine derivatives, which, in turn, can be transformed into quinoxalines, benzotriazoles, and benzimidazoles. Various organometallic reactions of the Ugi-Smiles adducts have been successfully carried out, either from iodophenols (Heck couplings to give indoles, Ullmann reaction to form quinoxalines), or from allyl pyrimidines (azepine formation by RCM strategy) as starting phenol inputs. Finally, a new palladium-mediated oxidative cyclization led to the formation of tricyclic systems.
Molecular Diversity 08/2009; 14(4):855-67. · 3.15 Impact Factor
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ABSTRACT: The coupling of an acyl chloride with an isocyanide affords 2,5-disubstituted oxazoles under mild basic conditions instead of 4,5-disubstituted derivatives when using Schöllkopf conditions (butyllithium); this reaction constitutes a remarkable example of a base-induced chemoselective process in isocyanide chemistry.
Chemical Communications 08/2009; · 6.17 Impact Factor
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Annalen der Chemie und Pharmacie 10/2008; 2008(35):5974 - 5987. · 3.10 Impact Factor
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ABSTRACT: Oxidative cleavage and cyclization cascades of N-aryl peptides have been achieved under palladium catalysis with air as the sole stoichiometric oxidant.
Chemical Communications 04/2008; · 6.17 Impact Factor
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ABSTRACT: A new strategy involving Ugi-Smiles coupling followed by ring-closure metathesis is described herein for the preparation of pyrimidine-fused heterocyclic scaffolds. The scope of this sequence is presented in relation with the heteroatom effect observed in the Ugi-Smiles coupling.
The Journal of Organic Chemistry 08/2007; 72(15):5835-8. · 4.45 Impact Factor
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ABSTRACT: The use of Smiles rearrangement in Ugi- and Passerini-type couplings with electron-deficient phenols allows very straightforward multicomponent formation of O-aryl- and N-arylamides. Best yields were observed with the highly activated o- and p-nitrophenols, salicylic derivatives giving adducts in lower yields. The scope of these new reactions is further increased by the successful couplings of heterocyclic phenols such as hydroxypyridines and hydroxypyrimidines.
The Journal of Organic Chemistry 06/2007; 72(11):4169-80. · 4.45 Impact Factor
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ABSTRACT: Herein, we wish to report a new three-component formation of heterocyclic scaffolds based on a one-pot process from simple phenols. The key step of this procedure involves an ortho-quinone methide formation from Mannich adducts under alkylative conditions. The transient o-quinone methide has been trapped in situ with indole and diketone using lithium perchlorate as catalyst. The interest of this procedure has been furthermore demonstrated by a new three-component aminobenzofuran formation from phenols, aldehydes and isocyanides.
Organic & Biomolecular Chemistry 10/2006; 4(18):3410-3. · 3.70 Impact Factor
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Angewandte Chemie International Edition 01/2006; 44(48):7961-4. · 13.45 Impact Factor
