- N-heterocycles from chromium aminocarbenes
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The initial [2 + 2]-cycloadduct between a chromium aminocarbene and a tethered alkene undergoes a β-hydrogen elimination very efficiently when triphenylphosphine is added as a ligand. The reaction gives cyclic enamines or homoenamines depending on the sub
- Déry, Martin,Assouvie, Kevin,Heinrich, Nora,Rajotte, Isabelle,Lefebvre, Louis-Philippe D.,Legault, Marc-André,Spino, Claude
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- Formamides as Lewis Base Catalysts in SNReactions—Efficient Transformation of Alcohols into Chlorides, Amines, and Ethers
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A simple formamide catalyst facilitates the efficient transformation of alcohols into alkyl chlorides with benzoyl chloride as the sole reagent. These nucleophilic substitutions proceed through iminium-activated alcohols as intermediates. The novel method, which can be even performed under solvent-free conditions, is distinguished by an excellent functional group tolerance, scalability (>100 g) and waste-balance (E-factor down to 2). Chiral substrates are converted with excellent levels of stereochemical inversion (99 %→≥95 % ee). In a practical one-pot procedure, the primary formed chlorides can be further transformed into amines, azides, ethers, sulfides, and nitriles. The value of the method was demonstrated in straightforward syntheses of the drugs rac-Clopidogrel and S-Fendiline.
- Huy, Peter H.,Motsch, Sebastian,Kappler, Sarah M.
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supporting information
p. 10145 - 10149
(2016/08/16)
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- N-Formylsaccharin: A new formylating agent
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N-Formylsaccharin, a very cheap reagent, has been revealed to be an efficient and chemoselective formylating agent of amines. Georg Thieme Verlag Stuttgart New York.
- Cochet, Thomas,Bellosta, Véronique,Greiner, Alfred,Roche, Didier,Cossy, Janine
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experimental part
p. 1920 - 1922
(2011/10/02)
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- Photochemical and thermal isomerization processes of a chiral auxiliary based donor-acceptor substituted chiroptical molecular switch: Convergent synthesis, improved resolution and switching properties
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A new type of chiroptical molecular switch is presented where irradiation employing different wavelengths of light induces a reversible helix inversion of a sterically overcrowded alkene bearing a second chiral entity in the form of a stereogenic center present in a pyrrolidine unit. The additional stereogenic center in the chiral auxiliary group has a distinct influence on the switching selectivity of this system and greatly facilitates the resolution of the different diastereoisomers, which is a considerable improvement compared with previously reported systems. In addition, the pyrrolidine stereogenic center causes small energetic differences between the various states of the switch system resulting in a small but significant directional preference in the helix inversion steps.
- Van Delden, Richard A.,Hurenkamp, Johannes H.,Feringa, Ben L.
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p. 2845 - 2853
(2007/10/03)
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- Synthesis of C2-symmetrical bis-β-amino alcohols and their application in the enantioselective addition of diethylzinc to aldehydes
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The C2-symmetrical bis-β-amino alcohols 1-6 were prepared and especially attention is focused on bridges, which link the two β-amino alcohol units. These ligands have been applied as chiral catalysts in the asymmetric addition of diethylzinc to aldehydes. sec-Alcohols have been obtained in good yields with up to 95.4% enantiomeric excess.
- Xu, Qianyong,Wang, Hui,Pan, Xinfu,Chan, Albert S.C,Yang, Teng-Kuei
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p. 6171 - 6173
(2007/10/03)
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