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[reaction: see text] The addition of nucleophiles to 3-substituted pyridinium salts prepared from N-methylbenzamide and various pyridines has been investigated. Good to excellent regioselectivities favoring the 2,3-disubstituted 1,2-dihydropyridines were observed. The resulting 1,2-dihydropyridines led to the corresponding 2,3-disubstituted pyridines upon treatment with Mn(OAc)3/NaIO4. This methodology was also successfully applied to the enantioselective syntheses of (-)-L-733,061 and (-)-CP-99,994, two members of a new class of highly potent, nonpeptide, Substance P antagonists. 相似文献
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A highly enantioselective (up to 97.5% ee) and diastereoselective (95:5 dr trans/cis) Cu(I)-catalyzed cyclopropanation of alkenes using phenyliodonium ylide generated in situ from iodosobenzene and methyl nitroacetate is reported. The cyclopropanation took place with high enantioselectivity for a wide range of alkenes, and the reaction was performed at room temperature. 1-Nitrocyclopropyl esters are versatile building blocks to access the corresponding cyclopropane amino esters and aminocyclopropanes in two and three steps, respectively, from commercially available products. 相似文献
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As part of a research program directed toward the synthesis of Lycopodium alkaloids, a multigram scale asymmetric synthesis of intermediate 11 was achieved in 11 steps from pyridine (17). In addition to our alkene metathesis strategy, a key feature of this synthetic approach consists of a Fukuyama's Diels-Alder cycloaddition between 1,2-dihydropyridine and acrolein using MacMillan's catalyst (18) on a 50 g scale. This led to a 12-step catalytic asymmetric synthesis of (+)-luciduline (1). A broader subset of Lycopodium alkaloids could also be obtained, as demonstrated by the derivatization of 11 into advanced intermediates for the synthesis of some of these natural products. 相似文献
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We have developed an efficient catalytic enantioselective hydrogenation of pyridine derivatives. Enhanced reactivity was possible by an optimization of the electronic properties of the catalyst through ligand modification. This methodology shows the particular reactivity of N-iminopyridinium ylides that provides access to substituted piperidines in good enantiomeric excesses. 相似文献
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[reaction: see text] The stereoselective synthesis of pyridinones was accomplished by the nucleophilic addition of Grignard reagents to a chiral pyridinium salt derived from 4-methoxypyridine. This methodology was applied to an expedient synthesis of (-)-barrenazine A and B. After N-functionalization and 1,4-reduction of the pyridinone system, the corresponding alpha-amino piperidinones readily undergo dimerization to give the hexahydrodipyridinopyrazine skeleton of the barrenazine alkaloids. 相似文献
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Lifchits O Alberico D Zakharian I Charette AB 《The Journal of organic chemistry》2008,73(17):6838-6840
Nucleophilic ring opening of methyl 1-nitrocyclopropanecarboxylates by phenol derivatives in the presence of Cs2CO3 is described. The reaction tolerates a variety of substituents on both the aromatic alcohol and the cyclopropane and affords the products in good yields (53-84%) and with complete preservation of the enantiomeric excess at C-4. The methodology was applied in an enantioselective synthesis of the norepinephrine reuptake inhibitor atomoxetine (Strattera). 相似文献
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This communication describes a new tandem metathesis reaction for which an RC-ROM mechanism was experimentally supported. This process was successfully applied to the synthesis of cis-fused polyhydroquinolines enabling a short stereoselective total synthesis of ent-lepadin B. 相似文献