- Asymmetric Synthesis of Functionalized Tricyclic Chromanes via an Organocatalytic Triple Domino Reaction
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A highly stereoselective triple domino reaction for the synthesis of functionalized tricyclic chromane scaffolds has been developed. A secondary amine-catalyzed domino Michael/Michael/aldol condensation reaction between aliphatic aldehydes, nitro-chromene
- Kumar, Mukesh,Chauhan, Pankaj,Valkonen, Arto,Rissanen, Kari,Enders, Dieter
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- Intensified synthesis of [3,4-d]triazole-fused chromenes, coumarins, and quinolones
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Abstract: Efficient and metal-free synthesis of [3,4-d]triazole-fused chromenes, coumarins, and quinolones has been achieved in an intensified regime using microwave heating. The smooth 1,3-dipolar cycloaddition reaction of heterocyclic nitroalkenes with
- Schwendt, Georg,Glasnov, Toma
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- 1,4-addition of TMSCCl3 to nitroalkenes: Efficient reaction conditions and mechanistic understanding
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Improved synthetic conditions allow preparation of TMSCCl3 in good yield (70 %) and excellent purity. Compounds of the type NBu4X [X=Ph3SiF2 (TBAT), F (tetrabutylammonium fluoride, TBAF), OAc, Cl and Br] act as catalytic promoters for 1,4-additions to a range of cyclic and acyclic nitroalkenes, in THF at 0-25 °C, typically in moderate to excellent yields (37-95 %). TBAT is the most effective promoter and bromide the least effective. Multinuclear NMR studies (1H, 19F, 13C and 29Si) under anaerobic conditions indicate that addition of TMSCCl3 to TBAT (both 0.13 M) at -20 °C, in the absence of nitroalkene, leads immediately to mixtures of Me3SiF, Ph3SiF and NBu4CCl3. The latter is stable to at least 0 °C and does not add nitroalkene from -20 to 0 °C, even after extended periods. Nitroalkene, in the presence of TMSCCl3 (both 0.13 M at -20 °C), when treated with TBAT, leads to immediate formation of the 1,4-addition product, suggesting the reaction proceeds via a transient [Me 3Si(alkene)CCl3] species, in which (alkene) indicates an Si O coordinated nitroalkene. The anaerobic catalytic chain is propagated through the kinetic nitronate anion resulting from 1,4 CCl3 - addition to the nitroalkene. This is demonstrated by the fact that isolated NBu4[CH2=NO2] is an efficient promoter. Use of H2C=CH(CH2)2CH=CHNO 2 in air affords radical-derived bicyclic products arising from aerobic oxidation. Understanding TMSCCl3: The synthesis and reactivity of TMSCCl3 has been investigated. The mechanism of 1,4-CCl3 addition to nitroalkenes begins with nitroalkene coordination, followed by the attack of an external fluoride ion, and does not involve the formation of NBu4[Me3SiFCCl3] (see figure).
- Wu, Na,Wahl, Benoit,Woodward, Simon,Lewis, William
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supporting information
p. 7718 - 7724
(2014/07/07)
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- Assessment of dopamine D1 receptor affinity and efficacy of three tetracyclic conformationally-restricted analogs of SKF38393
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To assess the effect of conformational mobility on receptor activity, the β-phenyl substituent of dopamine D1 agonist ligands of the phenylbenzazepine class, (±)-6,6a,7,8,9,13b-hexahydro-5H-benzo[d] naphtho[2,1-b]azepine-11,12-diol (8), and its oxygen and sulfur bioisosteres 9 and 10, respectively, were synthesized as conformationally-restricted analogs of SKF38393, a dopamine D1-selective partial agonist. Compounds trans-8b, 9, and 10 showed binding affinity comparable to that of SKF38393, but functionally, they displayed only very weak agonist activity. These results suggest that the conformationally-restricted structure of the analogs cannot adopt a binding orientation that is necessary for agonist activity.
- Clark, Alia H.,McCorvy, John D.,Watts, Val J.,Nichols, David E.
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experimental part
p. 5420 - 5431
(2011/10/30)
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- Efficient conjugate addition of carbonyl compounds to 3-nitro-2H-chromenes in the presence of bases
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The conjugate addition of aldehydes and ketones to 3-nitro-2H-chromenes under basic conditions has been explored. A series of inorganic and organic bases were examined. Proline combined with NaOAc was found to act as an efficient catalyst for the reaction
- Hu, Zhi-Peng,Zhang, Jun-Min,Lou, Chun-Liang,Wang, Jin-Jia,Nie, Shao-Zhen,Yan, Ming
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experimental part
p. 17 - 33
(2011/03/17)
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