- Quaternary Ammonium Salts as Alkylating Reagents in C-H Activation Chemistry
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A rhodium(I)-catalyzed alkylation reaction of benzylic amines via C(sp3)-H activation using quaternary ammonium salts as alkyl source is described. The reaction proceeds via in situ formation of an olefin via Hofmann elimination, which is the actual alkylating reagent. This represents an operationally simple method for substituting gaseous and liquid olefins with solid quaternary ammonium salts as alkylating reagents, which is transferable to other C-H activation protocols as well.
- Spettel, Manuel,Pollice, Robert,Schnürch, Michael
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- A convenient palladium-catalyzed azaindole synthesis
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A one-pot protocol is described which allows direct access to azaindoles from amino-halopyridines and ketones.
- De Gasparo, Raoul,Lustenberger, Philipp,Mathes, Christian,Schlama, Thierry,Veitch, Gemma E.,Le Paih, Jacques J. M.
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- A convenient palladium-catalyzed azaindole synthesis
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A one-pot protocol is described which allows direct access to azaindoles from amino-halopyridines and ketones.
- De Gasparo, Raoul,Lustenberger, Philipp,Mathes, Christian,Schlama, Thierry,Veitch, Gemma E.,Le Paih, Jacques J. M.
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supporting information
p. 197 - 200
(2015/03/03)
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- A metal-free tandem demethylenation/C(sp2)-H cycloamination process of N -Benzyl-2-aminopyridines via C-C and C-N bond cleavage
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A mild, metal-free synthesis of pyrido[1,2-a]benzimidazoles starting with N-benzyl-2-aminopyridines, which employs PhI(OPiv)2 as a stoichiometric oxidant, has been developed. The process is initiated by an unusual PhI(OPiv)2-mediated ipso SEAr reaction, followed by solvent-assisted C-C and C-N bond cleavage.
- Liang, Dongdong,He, Yimiao,Liu, Lanying,Zhu, Qiang
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supporting information
p. 3476 - 3479
(2013/07/26)
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- Mechanistic investigations and substrate scope evaluation of ruthenium-catalyzed direct sp3 arylation of benzylic positions directed by 3-substituted pyridines
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A highly efficient direct arylation process of benzylic amines with arylboronates was developed that employs Ru catalysis. The arylation takes place with greatest efficiency at the benzylic sp3 carbon. If the distance to the activating aryl ring is increased, arylation is still possible but the yield drops significantly. Efficiency of the CH activation was found to be significantly increased by use of 3-substituted pyridines as directing groups, which can be removed after the transformation in high yield. Calculation of the energy profile of different rotamers of the substrate revealed that presence of a substituent in the 3-position favors a conformation with the CH2 group adopting a position in closer proximity to the directing group and facilitating C-H insertion. This operationally simple reaction can be carried out in argon atmosphere as well as in air and under neutral reaction conditions, displaying a remarkable functional group tolerance. Mechanistic studies were carried out and critically compared to mechanistic reports of related transformations.
- Dastbaravardeh, Navid,Kirchner, Karl,Schnuerch, Michael,Mihovilovic, Marko D.
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p. 658 - 672
(2013/02/26)
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- Aryl bromides and aryl chlorides for the direct arylation of benzylic amines mediated by ruthenium(II)
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The ruthenium(II)-catalyzed sp3 C-H bond arylation of benzylic amines with aryl halides is reported. In the present method, aryl iodides and, more importantly, also the cheaper aryl bromides and aryl chlorides can be applied as aryl sources. Additionally, the method does not require elaborate manipulations in a glove box and can be carried out in simple screw cap vials. Potassium pivalate proved to be beneficial for the transformation with aryl bromides or iodides as aryl source, but was not required for aryl chlorides. In the latter case, the addition of PPh3 led to high conversion. 3-Methyl and 3-phenyl pyridine were established as directing groups, and the substituent in the 3-position represents a key structural feature for high conversion. The directing group can be cleaved after the transformation, which allows access to diarylmethylamines. Mechanistic studies were carried out and critically compared to mechanistic reports of related transformations.. Copyright
- Dastbaravardeh, Navid,Schnuerch, Michael,Mihovilovic, Marko D.
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p. 2878 - 2890
(2013/06/27)
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- Ruthenium(0)-catalyzed sp3 C-H bond arylation of benzylic amines using arylboronates
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A Ru-catalyzed direct arylation of benzylic sp3 carbons of acyclic amines with arylboronates is reported. This highly regioselective and efficient transformation can be performed with various combinations of N-(2-pyridyl) substituted benzylamines and arylboronates. Substitution of the pyridine directing group in the 3-position proved to be crucial in order to achieve high arylation yields. Furthermore, the pyridine directing group can be removed in high yields via a two-step protocol.
- Dastbaravardeh, Navid,Schnuerch, Michael,Mihovilovic, Marko D.
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supporting information; experimental part
p. 1930 - 1933
(2012/05/31)
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- Regioselective syntheses of 2,3-substituted pyridines by orthogonal cross-coupling strategies
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2-Aryl/alkylamino-3-aryl I and 3-aryl/alkylamino-2-aryl pyridines II, as important potentially bioactive compounds, were synthesized by applying orthogonal cross-coupling strategies. Combinations of the Suzuki-Miyaura, Liebeskind-Srogl, and Buchwald-Hartwig protocols gave access to the title compounds in a straightforward and operationally simple manner. Full control over the regioselectivity at the 2- and 3-positions was achieved by using 2,3-dichloropyridine or 3-iodo-2-(methylthio)pyridine as simple, commercially available starting materials. Within this contribution, efficient and high yielding conditions were developed for the Suzuki-Miyaura cross-coupling reaction of 2-substituted 3-chloropyridines, a transformation formerly underrepresented in the literature. For the synthesis of 3-alkyl/arylamino-2- aryl pyridines, the stability of the methylthio group was exploited under Pd-catalysis in the absence of a copper source. This even enabled the development of an operationally highly facile (semi)-one-pot protocol to access the aforementioned compound class that avoided one purification step. A series of products I and II was prepared by using the developed protocols with excellent regioselectivity and good yields. Copyright
- Koley, Moumita,Wimmer, Laurin,Schnuerch, Michael,Mihovilovic, Marko D.
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supporting information; experimental part
p. 1972 - 1979
(2011/04/27)
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