139285-03-3Relevant academic research and scientific papers
Amine Catalysis with Substrates Bearing N-Heterocyclic Moieties Enabled by Control over the Enamine Pyramidalization Direction
M?hler, Jasper S.,Schnitzer, Tobias,Wennemers, Helma
supporting information, p. 15623 - 15628 (2020/10/29)
Stereoselective organocatalytic C?C bond formations that tolerate N-heterocycles are valuable since these moieties are common motifs in numerous chiral bioactive compounds. Such transformations are, however, challenging since N-heterocyclic moieties can i
Enantio- and diastereoselective michael addition reactions of unmodified aldehydes and ketones with nitroolefins catalyzed by a pyrrolidine sulfonamide
Wang, Jian,Li, Hao,Lou, Bihshow,Zu, Liansuo,Guo, Hua,Wang, Wei
, p. 4321 - 4332 (2008/02/06)
Chiral (S)-pyrrolidine trifluoromethanesulfonamide has been shown to serve as an effective catalyst for direct Michael addition reactions of aldehydes and ketones with nitroolefins. A wide range of aldehydes and ketones as Michael donors and nitroolefins as acceptors participate in the process, which proceeds with high levels of enantioselectivity (up to 99% ee) and diastereoselectivity (up to 50:1 d.r.). The methodology has been employed successfully in an efficient synthesis of the potent H., agonist Sen 50917. In addition, a practical three-step procedure for the preparation of (S)-pyrrolidine trifluorometh-anesulfonamide has been developed. The high levels of stereochemical control attending Michael addition reactions catalyzed by this pyrrolidine sulfonamide, have been investigated by using ab initio and density functional methods. Transition state structures for the rate-limiting C-C bond-forming step, corresponding to re- and si-face addition to the reactive conformation of the key enamine intermediates have been calculated. Analysis of these structures indicates that hydrogen bonding plays an important role in catalysis and that the energy barrier for si-face attack in reactions of aldehydes to form 2R,3S products is lower than that for the re-face attack leading to 2S,3R products. In contrast, the energy barrier for re-face addition is lower than that for si-face addition in reactions of ketones. The computational results, which are in good agreement with the experimental observations, are discussed in the context of the stereo-chemical course of these Michael addition reactions.
DIRECT ORGANOCATALYTIC ASYMMETRIC REACTIONS OF ENOLIZABLE α-AMINO ALDEHYDES OR KETONES TO FORM HIGHLY ENANTIOMERICALLY ENRICHED AMINE PRODUCTS
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Page/Page column 48, (2010/10/20)
A method for asymmetrically forming a (diprotectedamino)-product having a chiral center and in which one enantiomer is in excess over the other is disclosed. The method comprises reacting an enolizable alpha- (diprotectedamino)-aldehyde or -ketone donor molecule with an excess of an unsaturated acceptor molecule that has one or no hydrogen atoms bonded to a carbon atom alpha to the carbon of the unsaturation. The donor and acceptor molecules are dissolved or dispersed in a liquid solvent and are in the presence of a chiral amine catalyst to form an addition product reaction medium. The reaction medium is maintained for a time sufficient to form an α-(diprotectedamino)-aldehyde or -ketone product having a chiral center formed at a carbon atom bonded to the α-(diprotectedamino) group and in which one enantiomer is in excess over the other.
Synthesis of New 4,5,6,7-Tetrahydro-3H-imidazo[4,5-c]pyridine Derivatives
Brana, Miguel F.,Guisado, Cristina,Sanz, Francisca
, p. 917 - 923 (2007/10/03)
The synthesis of new ligands for the H3 histamine receptor is described. These new compounds are spinacine derivatives obtained by alkylation or Michael reaction at C6 position.
Diels-Alder Reaction of (E)-4-(2-Nitroethenyl)-1H-imidazoles and Methyl (E)-3-(1-Imidazol-4-yl)propenoates
Kosaka, Keigo,Maruyama, Kazumi,Nakamura, Haruko,Ikeda, Masazumi
, p. 1941 - 1944 (2007/10/02)
Diels-Alder reaction of methyl (E)-3-(1H-imidazol-4-yl)propenoates 2, 3a-c and (E)-4-(2-nitroethenyl)-1H-imidazoles 3d,e with 2,3-dimethyl-1,3-butadiene, cyclopentadiene, and cyclohexa-1,3-diene gave the corresponding cycloadducts 6-9.
