- Enantioselective Nickel-Catalyzed Alkyne-Azide Cycloaddition by Dynamic Kinetic Resolution
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The triazole heterocycle has been widely adopted as an isostere for the amide bond. Many native amides are α-chiral, being derived from amino acids. This makes α-N-chiral triazoles attractive building blocks. This report describes the first enantioselective triazole synthesis that proceeds via nickel-catalyzed alkyne-azide cycloaddition (NiAAC). This dynamic kinetic resolution is enabled by a spontaneous [3,3]-sigmatropic rearrangement of the allylic azide. The 1,4,5-trisubstituted triazole products, derived from internal alkynes, are complementary to those commonly obtained by the related CuAAC reaction. Initial mechanistic experiments indicate that the NiAAC reaction proceeds through a monometallic Ni complex, which is distinct from the CuAAC manifold.
- Liu, En-Chih,Topczewski, Joseph J.
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supporting information
p. 5308 - 5313
(2021/05/04)
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- Enantioselective Copper Catalyzed Alkyne-Azide Cycloaddition by Dynamic Kinetic Resolution
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The copper(I) catalyzed alkyne-azide cycloaddition (CuAAC), a click reaction, is one of the most powerful catalytic reactions developed during the last two decades. Conducting CuAAC enantioselectively would add a third dimension to this reaction and would
- Liu, En-Chih,Topczewski, Joseph J.
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supporting information
p. 5135 - 5138
(2019/03/29)
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- Electrophilic Trifluoromethylthiolation/Semipinacol Rearrangement: Preparation of β-SCF3 Carbonyl Compounds with α-Quaternary Carbon Center
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A new and modular electrophilic trifluoromethylthiolation/semipinacol rearrangement of allylic silyl ethers has been developed under mild conditions. This approach allows the formation of a number of β-SCF3 carbonyl compounds with a cyclic and all-carbon quaternary center framework in moderate to good yields. It should be noted that this achievement is a metal-free process and just requires the use of simple acetyl chloride as an acidic promoter. Additionally, an interesting H-migration in competition with aryl-migration process was revealed.
- Xi, Chao-Chao,Chen, Zhi-Min,Zhang, Shu-Yu,Tu, Yong-Qiang
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supporting information
p. 4227 - 4230
(2018/07/29)
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- Acid-catalyzed hydration of alkynes in aqueous microemulsions
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Terminal aromatic alkynes are converted rapidly into ketones in a regioselective manner by treatment of their microemulsions with 0.33 M mineral acid between 80 and 140 °C. Internal and aliphatic acetylenes are likewise hydrated, but require longer reaction periods. The products are easily isolated from the reaction mixtures by phase separation. Replacement of H2O by D2O leads to the formation of trideuteriomethyl ketones. Copyright
- Nairoukh, Zackaria,Avnir, David,Blum, Jochanan
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p. 430 - 432
(2013/04/24)
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- ANODIC FUNCTIONALIZATION OF OLEFINS IN ALCOHOLS IN THE PRESENCE OF HALIDE SALTS
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Electrolysis of conjugated, unbranched arylolefins in the presence of alkali metal halides in alcohols affords 1-aryl-2-bromoketals in 60-90percent yields.Under these conditions, 2-methyl-1-phenylprop-1-ene is converted into 1-bromo-2-methyl-1-phenylprop-1-ene in 80percent yield, and arylolefins with no benzylidene hydrogens give 1-aryl-1-alkoxy-2-bromoalkanes.
- Elinson, M. N.,Makhova, I. V.,Nikishin, G. I.
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p. 112 - 118
(2007/10/02)
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- Halogenative Deoxygenation of Ketones; Vinyl Bromides and/or gem-Dibromides by Cleavage of 1,3-Benzodioxoles (Ketone Phenylene Acetals) with Boron Tribromide
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Representative ketones 1 have been converted in generally good yields to the respective 1,3-benzodioxoles 5 by trans-acetalization of ketone dimethyl acetals with 1,2-dihydroxybenzene, and cleaved with boron tribromide. 1,3-Benzodioxoles derived from α-unbranched aliphatic ketones gave in general a mixture of vinyl bromides and gem-dibromides; pure gem-dibromides could be selectively obtained in most of cases using a suitable reaction time. 1,3-Benzodioxoles derived from α-branched ketones gave complex mixtures and their cleavage appears to be of little synthetic signifance. 1,3-Benzodioxoles of aromatic ketones gave vinyl bromides only.Aliphatic cyclic gem-dibromides 3 were converted to the respective vinyl bromides 2 by phase-transfer-catalysed dehydrobromination.
- Napolitano, Elio,Fiaschi, Rita,Mastrorilli, Ettore
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p. 122 - 125
(2007/10/02)
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- Decomposition et proprietes electrophiles des carbenoides monohalogenes non fonctionnels
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Geminal substitution of a carbon atom by a halogen atom and a lithium atom gives rise to electrophilic properties and great instability to the corresponding α-monohalogenoalkyllithium.From NMR data, it appears that the functional carbon atom exhibits an electron deficiency in connection with an intramolecular halogen-lithium coordination.This description is in agreement with the structure proposed for LiCH2F on the basis of "ab initio" calculations.Electronic and steric effects of the other substituents of the functional carbon atom and the influence of the reaction medium (basicity of solvents, Lewis acidity of associated salts) on the variation of electrophilic and nucleophilic behaviour and stability of carbenoids (mono, di, trihalogeno) can be rationalized on the basis of this metallocarbenium halogenide structure.
- Villieras, J.,Rambaud, M.,Kirschleger, B.,Tarhouni, R.
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p. 837 - 843
(2007/10/02)
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- SELECTIVITY OF MONOMERIC METAPHOSPHATE REACTIONS WITH ALCOHOLS IN POLAR APROTIC SOLVENTS
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Evidence is presented for selectivity in the reaction of metaphosphate, PO3(1-), with methanol in preference to t-butanol in acetonitrile solution.In dichloromethane solution there is also evidence for preferential nucleophilic solvation of reactant by methanol vs. t-butanol.
- Ramirez, Fausto,Marecek, James F.,Yemul, Shrishailam S.
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p. 1515 - 1518
(2007/10/02)
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