- The Direct Conversion of α-Hydroxyketones to Alkynes
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Alkynes are highly important functional groups in organic chemistry, both as part of target structures and as versatile synthetic intermediates. In this study, a protocol for the direct conversion of α-hydroxyketones to alkynes is reported. In combination with the variety of synthetic methods that generate the required starting materials by forming the central C-C bond, it enables a highly versatile fragment coupling approach toward alkynes. A broad scope for this novel transformation is shown alongside mechanistic insights. Furthermore, the utility of our protocol is demonstrated through its application in concert with varied α-hydroxyketone syntheses, giving access to a broad spectrum of alkynes.
- Ghiringhelli, Francesca,Nattmann, Lukas,Bognar, Sabine,Van Gemmeren, Manuel
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p. 983 - 993
(2019/01/24)
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- Enantioselective aerobic oxidation of α-hydroxy-ketones catalyzed by oxidovanadium(V) methoxides bearing chiral, N-salicylidene- tert -butylglycinates
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Chiral oxidovanadium(V) methoxides prepared from 3,5-disubstituted-N- salicylidene-l-tert-butylglycines and vanadyl sulfate in air-saturated MeOH serve as highly enantioselective catalysts for asymmetric aerobic oxidations and kinetic resolution of alkyl, aryl, and heteroaryl α-hydroxy-ketones with differed α-substituents at ambient temperature in toluene or TBME (tert-butyl methyl ether). The best scenarios involve the use of complexes which bear the tridendate templates derived from 3,5-diphenyl- or 3-o-biphenyl-5-nitro-salicyaldehyde. The kinetic resolution selectivities of the aerobic oxidation process are in the range of 12 to >1000 based on the selectivity factors (krel).
- Chen, Chien-Tien,Kao, Jun-Qi,Salunke, Santosh B.,Lin, Ya-Hui
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- Aerobic oxidative iodination of ketones catalysed by sodium nitrite "on water" or in a micelle-based aqueous system
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Selective and efficient aerobic oxidative iodination of ketones in aqueous media was achieved by using molecular iodine as the source of iodine atoms, air as the terminal oxidant, sodium nitrite (NaNO2) as the catalyst and H2SO4
- Stavber, Gaj,Iskra, Jernej,Zupan, Marko,Stavber, Stojan
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scheme or table
p. 1262 - 1267
(2010/05/02)
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- Al Lewis acid-catalyzed regiodivergent 1,2-rearrangement of α-siloxy aldehydes: scope and mechanism
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Regiodivergent 1,2-rearrangement of α-siloxy aldehydes bearing α-aryl and α-alkyl substituents into α-siloxy ketones has been realized by using different Al Lewis acid catalyst/solvent systems. The scope of this unprecedented protocol has been investigate
- Ohmatsu, Kohsuke,Tanaka, Takayuki,Ooi, Takashi,Maruoka, Keiji
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experimental part
p. 7516 - 7522
(2009/12/04)
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- Complete switch of migratory aptitude in aluminum-catalyzed 1,2-rearrangement of differently α,α-disubstituted a-siloxy aldehydes
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(Chemical Equation Presented) Control of the migration tendency: The regiodivergent 1,2-rearrangement of asiloxy aldehydes bearing α-aryl and α-alkyl substituents into α-siloxy ketones has been realized by using different aluminum Lewis acid catalyst/solvent systems (see scheme). The scope of this unprecedented protocol has been investigated with various substrates and clearly demonstrates its utility for the selective synthesis of two structural isomers from one substrate.
- Ohmatsu, Kohsuke,Tanaka, Takayuki,Ooi, Takashi,Maruoka, Keiji
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supporting information; experimental part
p. 5203 - 5206
(2009/04/11)
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- Asymmetric dihydroxylation of disubstituted allenes
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Asymmetric dihydroxylation of 1,1-disubstituted and 1,3-disubstituted allenes can be used to synthesize chiral α-hydroxy ketones. We have also obtained α,α′-dihydroxy ketones with high enantioselectivity from 1,3-disubstituted allenes. Low conversion of the dihydroxylation of chiral allenes can be used as a kinetic resolution of sterically hindered allenes.
- Fleming, Steven A.,Liu, Renmao,Redd, J. Ty
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p. 8095 - 8098
(2007/10/03)
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- Asymmetric acyloin condensation catalysed by phenylpyruvate decarboxylase. Part 2: Substrate specificity and purification of the enzyme
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Phenylpyruvate decarboxylase from Achromobacter eurydice was used to catalyse the asymmetric acyloin condensation of phenylpyruvate 1 with various aldehydes 2 to produce optically active acyloins PhCH2COCH(OH)R 3. The specific activity of the phenylpyruvate decarboxylase enzyme was increased by a factor of 332 after its purification. The molecular weight of the purified enzyme was shown to be 150 kDa by gel filtration chromatography, while SDS gel electrophoresis showed two sub-units with molecular weights of 90 and 40 kDa. The acyloin condensation yield decreased with increasing chain length for straight chain aliphatic aldehydes from 76% for acetaldehyde to 24% for valeraldehyde. The e.e.s of the acyloin products were 87-98%. Low yields of acyloin products were obtained with chloroacetaldehyde (13%) and glycoaldehyde (16%). Indole-3-pyruvate was a substrate of the enzyme and provided acyloin condensation product 3-hydroxy-1-(3-indolyl)-2-butanone 5 with acetaldehyde in 19% yield, while benzoylformate was not a substrate for the enzyme.
- Guo, Zhiwei,Goswami, Animesh,Nanduri, Venkata B.,Patel, Ramesh N.
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p. 571 - 577
(2007/10/03)
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- Syntheses of Dialkyl and Functionalized Ketones via 1-(Benzotriazol-1-yl)alkyl Methyl Thioethers
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Benzotriazol-1-ylmethyl methyl thioether (1), after easy deprotonation by BuLi, reacted with alkyl halides to afford 1-(benzotriazol-1-yl)alkyl methyl thioethers 2 in good yields. The utility of compounds 2 as alkanoyl anion equivalents was demonstrated by the reactions of their anions with alkyl halides, aldehydes, ketones, esters, and phenyl isocyanate: the products were readily hydrolyzed to α-functionalized ketones in dilute aqueous acid.
- Katritzky, Alan R.,Oniciu, Daniela C.,Ghiviriga, Ion,Soti, Ferenc
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p. 2110 - 2115
(2007/10/03)
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- LICKOR-Promoted 1,2-elimination in 1,1-dimethoxy-2-phenylethane and 1,1-dimethoxy-2-phenylpropane: synthesis of substituted enol ethers and alkynes
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Dimethyl acetals of phenylacetaldehyde 1a and 2-phenylpropionaldehyde 1b, upon treatment with 1.25 equiv. of LICKOR reagent, undergo 1,2-elimination (THF at -95 deg C) promoted by metallation at the benzylic site, and afford the corresponding enol ethers in the E-form.When the substrate is treated with excess of the base (2.5 equiv.), further hydrogen-metal exchange takes place at the α-vinyl site of the elimination product, and carbonyl electrophiles can be added to the carbanionic intermediate yielding allyl alcohols.Experimental procedures are given for the conversion of the α-substituted derivatives into carbonyl compounds, according to an inverse polarity approach.Moreover, allyl alcohols synthesized starting from 1a, can be transformed into prop-2-ynyl alcohols by treatment with LICKOR base.
- Deagostino, Annamaria,Mella, Mariella,Prandi, Cristina,Venturello, Paolo
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p. 2757 - 2760
(2007/10/02)
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- Substituted (Carbazol-9-yl)(benzotriazol-1-yl)methanes: Novel Acyl Anion Equivalents
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Alkyl(carbazol-9-yl)(benzotriazol-1-yl)methanes are deprotonated by BuLi to form anions which react with alkyl halides, aldehydes, and isocyanates to afford the expected products and which add 1,4 to α,β-unsaturated ketones.These products are hydrolyzed by dilute acid at ambient temperature to afford the corresponding ketones.
- Katritzky, Alan R.,Yang, Zhijun,Lam, Jamshed N.
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p. 6917 - 6923
(2007/10/02)
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- ENANTIOSELECTIVE SYNTHESIS OF PROTECTED α-HYDROXY ALDEHYDES AND KETONES VIA HYDROXYLATION OF METALATED CHIRAL HYDRAZONES
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α-Benzyloxy aldehydes and α-acetoxy ketones 4 of high enantiomeric purity are prepared in good overall yields via oxaziridine mediated hydroxylation of chiral hydrazone azaenolates.As auxiliaries novel proline derived hydrazine reagents 5 are used.
- Enders, Dieter,Bhushan, Vidya
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p. 2437 - 2440
(2007/10/02)
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- PALLADIUM(0) CATALYSED ISOMERISATION OF 2,3-EPOXY ALCOHOLS TO α AND β- HYDROXY KETONES
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Isomerisation of 2,3-epoxy alcohols possessing an aryl group at 1 and/or 3 position, with Pd(PPh3)4 leads to formation of α and β-hydroxy ketones.
- Vankar, Yashwant D.,Chaudhuri, Narayan C.,Singh, Surendra P.
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p. 1621 - 1626
(2007/10/02)
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- REACTIONS OF ACYL ANIONS GENERATED FROM ACID CHLORIDES AND DIIODOSAMARIUM
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Acid chlorides react with SmI2 to give α-diketones.Various experiments show that the initially formed acyl radical is rapidly transformed into an acyl anion which is thus generated by quite an unusual route.This species acylates acid chlorides, aldehydes and ketones in situ to give α-diketones and α-diketols.There are some limitations to this acyl anion chemistry but the reactions are realized with a good efficiency at room temperature in THF solution.
- Souppe, J.,Namy, J-L.,Kagan, H.B.
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p. 2869 - 2872
(2007/10/02)
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- Preparation, reduction chimique et electrochimique d'α-nitrostyrylcetones - synthese d'heterocycles azotes
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Nitration of styryl ketones with nitrogen peroxide leads to the corresponding α-nitroethylenic ketones in good yield.However, the presence of methoxy groups involves a nitration on the aromatic nucleus.LiAlH4 reduction of α-nitrostyrylketones yields the c
- Marcot, Bernard,Rabaron, Alain,Viel, Claude,Bellec, Christian,Deswarte, Stephane,Maitte, Pierre
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p. 1224 - 1234
(2007/10/02)
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