- Efficient photolytic C-H bond functionalization of alkylbenzene with hypervalent iodine(iii) reagent
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A practical approach to radical C-H bond functionalization by the photolysis of a hypervalent iodine(iii) reagent is presented. The photolysis of [bis(trifluoroacetoxy)iodo]benzene (PIFA) leads to the generation of trifluoroacetoxy radicals, which allows the smooth transformation of various alkylbenzenes to the corresponding benzyl ester compounds under mild reaction conditions.
- Sakamoto, Ryu,Inada, Tsubasa,Selvakumar, Sermadurai,Moteki, Shin A.,Maruoka, Keiji
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supporting information
p. 3758 - 3761
(2016/03/25)
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- β-aryl nitrile construction via palladium-catalyzed decarboxylative benzylation of α-cyano aliphatic carboxylate salts
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The palladium-catalyzed decarboxylative benzylation of α-cyano aliphatic carboxylate salts with benzyl electrophiles was discovered. This reaction exhibits good functional group compatibility and proceeds under relatively mild conditions. A diverse range of quaternary, tertiary and secondary β-aryl nitriles can be conveniently prepared by this method. Copyright
- Shang, Rui,Huang, Zheng,Xiao, Xiao,Lu, Xi,Fu, Yao,Liu, Lei
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supporting information
p. 2465 - 2472,8
(2020/08/31)
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- Reaction pathway and rate-determining step of the Schmidt rearrangement/fragmentation: A kinetic study
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The Schmidt rearrangement of substituted 3-phenyl-2-butanone with trimethylsilyl azide in 90% (v/v) aqueous TFA gave two types of product, fragmentation and rearrangement, the ratio of which depends on the substituent: more fragmentation for a more electron-donating substituent. Rate measurements by azotometry indicated the presence of an induction period, and the pseudo-first-order rate constants showed saturation kinetics with respect to the azide concentration. It was indicated that the reaction proceeds through pre-equilibrium in the formation of iminodiazonium (ID) ion and that the N 2 liberation from the ID ion is rate-determining. Under high azide concentration conditions, where the effective reactant is the ID ion, the reaction gave a linear Hammett plot with a value of -0.50. The observed substituent effects on the rate and the product selectivity imply that path bifurcation on the way from the rate-determining TS to the product states occurs, as suggested by previous molecular dynamics simulations, in a similar manner to the analogous Beckmann rearrangement/fragmentation reactions.
- Akimoto, Ryo,Tokugawa, Takehiro,Yamamoto, Yutaro,Yamataka, Hiroshi
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experimental part
p. 4073 - 4078
(2012/06/29)
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- Zinc chloride enhanced arylations of secondary benzyl trifluoroacetates in the presence of b-hydrogen atoms
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Zinc or swim: Arylation of benzyl trifluoroacetates with arylzinc reagents in the presence of β- hydrogen atoms were realized under mild conditions. Both electron-rich and electron-deficient arene substrates were successfully arylated. This arylation method could offer a very versatile synthetic route to access a series of diversity-oriented diarylalkane motifs. TFA = trifluoroacetyl. Copyright
- Duan, Hui,Meng, Lingkui,Bao, Denghui,Zhang, Heng,Li, Yao,Lei, Aiwen
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supporting information; experimental part
p. 6387 - 6390
(2010/11/04)
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- Improved procedure for the reductive acetylation of acyclic esters and a new synthesis of ethers
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An optimized protocol for the DIBALH reductive acetylation of acyclic esters and diesters is described. This reductive acetylation procedure allows a wide variety of esters to be converted into the corresponding α-acetoxy ethers in good to excellent yields. It was found that, under mild acidic conditions, many α-acetoxy ethers can be further reduced to the corresponding ethers. This net two-step ester deoxygenation is an attractive alternative to the classical Williamson synthesis for certain ethers.
- Kopecky, David J.,Rychnovsky, Scott D.
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p. 191 - 198
(2007/10/03)
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- Eine allgemeine und effiziente Methode zur Monohydroxylierung von Alkanen
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Keywords: Alkane; Dioxirane; Hydroxylierungen; Oxidationen
- Asensio, Gregorio,Mello, Rossella,Gonzalez-Nunez, Maria Elena,Castellano, Gloria,Corral, Julia
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p. 196 - 198
(2007/10/03)
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- Oxidation of C2, C3 and Higher Alkanes by a Ruthenium-Oxo System
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Barium ruthenate, BaRuO3(OH)2, when dissolved in TFA-CH2Cl2 containing a few equivalents of 2,2'-bipyridine, generates a highly reactive ruthenium-oxo system that is capable of oxidizing ethane and propane at room temeprature with good yields.
- Lau, Tai-Chu,Mak, Chi-Keung
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p. 943 - 944
(2007/10/02)
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- Solvolytic Elimination Reactions of Tertiary α-CSNMe2-Substitutedd Systems
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The tertiary benzylic α-CSNMe2-substituted p-nitrobenzoates and trifluoroacetates of general structure Ar(CH3)C(CSNMe2)(OCOR), 7 and 8, solvolyze to give exclusively elimination products H2C=C(CSNMe2)Ar.A Hammett study gave a nonlinear correlation.Variation in rate with solvent ionizing power was small for the unsubstituted trifluoroacetate derivative of 8, and the β-CD3 isotope effect on rate was negligible.There is, however, a large isotope effect (2.5-2.8) in formation of the elimination product when Ph(CH2D)C(CSNMe2)(OCOCF3) solvolyzes.It is concluded that an intermediate must be involved sine the product-determining step and the rate-determining step have differing isotope effects.The likely intermediate is an α-CSNMe2-substituted cation as an ion pair), despite the fact that the reaction has few characteristics of a typical E1 reaction.Tertiary noorbornyl, cyclohexyl, and 2-propyl α-CSNMe2-substituted systems also react to give exclusively elimination products at rates far in excess of α-CONMe2 analogues.It is suggested that α-CSNMe2 cations are also intermediates and that these cations undergo proton loss at an early ion pair stage.These cations are proposed to derive substitantial stabilization by charge delocalization onto sulfur of the thiocarbonyl group. By way of contrast, the secondary system CH3CH(CSNMe2)(OCOCF3), 25, solvolyzes to give mainly a rearranged product CH3CH(CONMe2)(SCOCH3) via a KΔ mechanism involving neighboring thiocarbonyl participation leading to a cyclized ion.
- Creary, Xavier,Hatoum, Holia N.,Barton, Angela,Aldridge, Timothy E.
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p. 1887 - 1897
(2007/10/02)
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- Zinc-Promoted Reactions. 2. Ionic and Nonionic Pathways in the Reduction of Acetophenone and 2,2-Dimethyl-1-phenylpropan-1-one
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The Clemmensen reduction of acetophenone and related substrates (PhCHXCH3, X = Cl, OH, OAc) was investigated in anhyd AcOH and in the presence of LiCl, HCl, or TFA.Ethylbenzene, 1-acetoxy-1-phenylethane, 2,3-diphenyl-2,3-butanediol, and 2,3-diphenyl-2-butene were formed in yields strongly dependent on the experimental conditions.The formation of the hydrocarbon was favored in neat AcOH and in AcOH/HCl/LiCl.Ionic and nonionic pathways were recognized.In the presence of Cl-, the proposed mechanism involves the intermediacy of PhCH(CH3)Cl.The process may proceed via *- and the carbon radical PhC*(CH3)OZnX.The second SET may lead to a carbanion, quenched by the acid to give PhCH(CH3)OZnX, a precursor of PhCHXCH3 (X = OAc, Cl).Coupling reactions, involving different radical species, account for the formation of the dimeric compounds.In the reduction of 2,2-dimethyl-1-phenylpropan-1-one, the preponderance of addition reactions, mainly involving Cl-, can be explained by the difficult approach of zinc metal to the hindered carbonyl group.Only traces of neopentylbenzene were obtained, the main product being 2-methyl-3-phenyl-2-butene.The proposed mechanism requires that the first SET occurs on adduct PhCCl(OH)C(CH3)3 to produce 2,2-dimethyl-1-phenylpropan-1-ol, the precursor of the alkene.
- Luchetti, Luciana,Rosnati, Vittorio
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p. 6836 - 6839
(2007/10/02)
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- EFFECT OF THE NATURE OF THE ACYLATING AGENT ON THE ASYMMETRIC ACYLATION OF ALCOHOLS
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During the acylation of racemic 1-phenylethanol by the action of carboxylic acid anhydrides in the presence of S-(-)-N,N-dimethyl-α-phenylethylamine the unreacted alcohol is enriched in the S isomer.Its optical purity increases with increase in the steric demands of the anhydride from 2percent for acetic anhydride to 9percent for benzoic anhydride.When carboxylic acid chlorides are used, optically active 1-phenyl-1-chloroethane and bis-1-phenylethyl ether are isolated in addition to S-(-)-1-phenylethanol.
- Potapov, V. M.,Dem'yanovich, V. M.,Klebnikov, V. A.,Korovina, T. G.
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p. 1095 - 1097
(2007/10/02)
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- Addition of Trifluoroacetic Acid to Substituted Styrenes
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The rate of addition of CF3CO2H to a series of ring-substituted styrenes ArCH=CH2 with 100percent, 50percent, and 20percent solutions of the acid in CCl4 have been measured.The rate of addition of 100percent CF3CO2H to the isomeric 1-phenylpropenes and the rate of cis- to trans-stilbene isomerization by this acid are also reported.The rates are correlated with ?+ parameters of the substituents and with aqueous H2SO4-catalyzed hydrations of the same substrates.Deviations from the ?+ correlation occur with substituents capable of strong hydrogen bonding to the acidic solvents; these deviations are attributed to a decrease in substituent electron-donating ability caused by this interaction.All of the evidence supports a mechanism of rate-determining protonation on carbon (the AdE2 mechanism), with no detectable effects from ? complexation of the acids with the substrates.
- Allen, Annette D.,Rosenbaum, Murray,Seto, Nina O. L.,Tidwell, Thomas T.
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p. 4234 - 4239
(2007/10/02)
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- A KINETIC STUDY OF THE MECHANISM OF ESTERIFICATION OF 1-ARYLETHANOLS IN TRIFLUOROACETIC ACID
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Aryl substituent effects upon the rate constants for the esterification of a series of 1-arylethanols in trifluoroacetic acid are in accordance with a reverse AAL1 mechanism, for wich the Hammett reaction constant ρ=-3.69 has been determined by correlation with ?+ substituent constants.The rates of reaction are ca. 50-fold faster than those for corresponding benzyl alcohols which bear an electron-donating aryl substituent and which are also believed to undergo esterification in trifluoroacetic acid by the reverse AAL1 mechanism; the reverse AAC2 mechanism applies to benzyl alcohols which bear an electron-withdrawing aryl substituent.
- Gillen, Ciaran J.,Knipe, Anthony C.,Watts, William E.
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p. 597 - 600
(2007/10/02)
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