- Easy Access to 2,4-Disubstituted Cyclopentenones by a Gold(III)-Catalyzed A3-Coupling/Cyclization Cascade
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An efficient and convenient synthesis of 2,4-disubstituted cyclopentenones has been achieved through a Au(III)-catalyzed isomerization-A3-coupling/cyclization cascade. A possible mechanism involving an initial Au(III)-catalyzed isomerization, A3-type coupling, and cyclization via an enol intermediate is postulated.
- Hu, Xiwen,Li, Jian,Liu, Li,Xu, Yue,Zhu, Shangrong
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supporting information
p. 9478 - 9483
(2020/12/21)
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- Introducing catalytic lossen rearrangements: Sustainable access to carbamates and amines
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A new, highly efficient and environmentally benign catalytic variant of the Lossen rearrangement is described. Dimethyl carbonate (DMC) as green activation reagent of hydroxamic acids in presence of catalytic amounts of tertiary amine bases {1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 1,8-biazabicyclo 5.4.0 undec-7-ene (DBU), 1,4-diazabicyclo[2.2.2]octane (DABCO), and triethylamine} and small quantities of methanol initiate the rearrangement. Methyl carbamates were obtained in good to moderate yields when aliphatic hydroxamic acids were employed in this catalytic Lossen rearrangement; under the same conditions aromatic hydroxamic acids yielded anilines. Notably, the mixture of DMC/methanol was recycled several times without observing decreased yields, thus minimizing the produced waste. Moreover, several other organic carbonates were successfully employed in the introduced catalytic Lossen rearrangement procedure. Copyright
- Kreye, Oliver,Wald, Sarah,Meier, Michael A. R.
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- Total synthesis of (±)-armepavines and (±)-nuciferines from (2-nitroethenyl)benzene derivatives
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A concise route to armepavine 1 and nuciferine 2 and 3, which can be isolated from the leaves of Nelumbo nucifera (Nymphaceae), has been achieved in which the longest linear sequence is only six steps from commercially available benzaldehyde in 28%, 21%, and 20% overall yield, respectively. The key transformations in the synthesis are the radical cyclization of aryl bromide with Bu3SnH and the Pictet-Spengler reaction of N-substituted amine with aldehyde. Copyright Taylor & Francis Group, LLC.
- Chang, Chia-Fu,Huang, Chu-Yun,Huang, Yu-Chao,Lin, Kuan-Yu,Lee, Yean-Jang,Wang, Chau-Jong
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experimental part
p. 3452 - 3466
(2011/02/22)
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- Trapping of carbamic acid species with (trimethylsilyl)diazomethane
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Methoxycarbonylation of a variety of amines into the corresponding methyl carbamates was accomplished by allowing them to react with (trimethylsilyl) diazomethane TMSCHN2 under bubbling of CO2. The reaction was performed at room temperature for a period of ca. 2 h in benzene-MeOH (4/1 v/v), which was the solvent of choice. In this mixed solvent, undesirable bicarbonate is formed in equilibrium along with carbamate anion. Owing to the irreversibility in the esterification step by TMSCHN2, however, the yield of methyl carbamate can reach very high.
- Ito, Yoshikatsu,Ushitora, Hiromi
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p. 226 - 235
(2007/10/03)
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- Pictet-Spengler reactions in multiphasic supercritical carbon dioxide/CO2-expanded liquid media. In situ generation of carbamates as a strategy for reactions of amines in supercritical carbon dioxide
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Acyl-Pictet-Spengler cyclizations can be achieved in scCO 2/CO2-expanded liquid media via the in situ formation of carbamate derivatives of β-arylethylamines. The Royal Society of Chemistry 2005.
- Dunetz, Joshua R.,Ciccolini, Rocco P.,Froeling, Morgan,Paap, Scott M.,Allen, Andrew J.,Holmes, Andrew B.,Tester, Jefferson W.,Danheiser, Rick L.
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p. 4465 - 4467
(2007/10/03)
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- First Carbamates Conversion to Amides by Simple Alkyl Group Transfer from Trialkylalanes
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(Equation presented) N-Monosubstituted carbamates are cleanly converted to amides under treatment with trialkylaluminum. This reaction involves an aluminum-assisted internal delivery of alkyl groups. It can be applied to new and mild protecting group strategies for alcohols.
- El Kaim, Laurent,Grimaud, Laurence,Lee, Anabelle,Perroux, Yannick,Tirla, Cornelia
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p. 381 - 383
(2007/10/03)
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- 1-Ethoxy-3,4-dihydroisoquindines
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1-(2-Substituted-hydrazino)-3,4-dihydroisoquinolines, prepared in one process by alkylating the corresponding 3,4-dihydroisocarbostyrils, hydrazinolyzing the resulting 1-alkoxy-3,4-dihydroisoquinolines and condensing the resulting 1-hydrazIno-3,4-dihydroisoquinolines with aldehydes or ketones, and 1,1'-azinobis(1,2,3,4-tetrahydroisoquinolines), prepared by condensing corresponding 1-alkoxy-3,4-dihydroisoquinolines and 1-hydrazino-3,4-dihydroisoquinolines, are useful as antihypertensive agents and/or as antiinflammatory agents.
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