1603-73-2Relevant academic research and scientific papers
Selective transition metal-free aroylation of diarylmethanes with 2-acyl-imidazolium salts via acyl C–C bond cleavage
Gan, Li-She,Li, Jie,Li, Lin-Lin,Wang, Jia-Min,Yang, Fan,Zou, Dong
, (2020/11/13)
A highly chemoselective method is reported for the aroylation of simple diarylmethane derivatives via direct acyl C–C cleavage with 2-acyl-imidazolium salts under transition metal-free conditions. This represents a straightforward way to access a variety of sterically and electronically diverse 1,2,2-triarylethanones, a class of compounds with biological activities and various applications.
Migratory Insertion of Carbenes into Au(III)-C Bonds
Zhukhovitskiy, Aleksandr V.,Kobylianskii, Ilia J.,Wu, Chung-Yeh,Toste, F. Dean
supporting information, p. 466 - 474 (2018/03/21)
Migratory insertion of carbon-based species into transition-metal-carbon bonds is a mechanistic manifold of vast significance: it underlies the Fischer-Tropsch process, Mizoroki-Heck reaction, Ziegler-Natta and analogous late-transition-metal-catalyzed olefin polymerizations, and a number of carbonylative methods for the synthesis of ketones and esters, among others. Although this type of reactivity is well-precedented for most transition metals, gold constitutes a notable exception, with virtually no well-characterized examples known to date. Yet, the complementary reactivity of gold to numerous other transition metals would offer new synthetic opportunities for migratory insertion of carbon-based species into gold-carbon bonds. Here we report the discovery of well-defined Au(III) complexes that participate in rapid migratory insertion of carbenes derived from silyl- or carbonyl-stabilized diazoalkanes into Au-C bonds at temperatures ≥ -40 °C. Through a combined theoretical and experimental approach, key kinetic, thermodynamic, and structural details of this reaction manifold were elucidated. This study paves the way for homogeneous gold-catalyzed processes incorporating carbene migratory insertion steps.
Photochemical Pinacol Rearrangements of Unsymmetrical Diols
Mladenova, Gabriela,Singh, Gurmit,Acton, Austin,Chen, Lie,Rinco, Olga,Johnston, Linda J.,Lee-Ruff, Edward
, p. 2017 - 2023 (2007/10/03)
The photochemical pinacol reaction of a series of nonsymmetrical 9-fluorenyl-substituted vic-diols was investigated and compared with their acid-catalyzed thermal reaction. Unlike the thermal reaction, the radiation-induced processes involve only fluorenyl cations, as is reflected in differences of product distribution between the two reactions. From the product studies, substituent migratory aptitudes are reversed in the photochemical process, suggesting that kinetic control takes place under neutral conditions unlike the acid-catalyzed thermal reactions. The presence of fluorenyl cation intermediates and their lifetimes were established by laser flash spectroscopy studies.
Keto-enol tautomerism and hydration of 9-acylfluorenes
Harcourt, Myles P.,O'Ferrall, Rory A. More
, p. 1415 - 1426 (2007/10/02)
Keto-enol tautomeric constants and ionisation constants heve been measured for the keto and enol tautomeers of 9-formyl-, 9-acetyl- and 9-benzoyl-fluorene in aqueous solution at 25 deg C.Values of pKE(KE=/ and pKE=-log KE) are -1.22, 2.28 and 1.91, respectively, and the corresponding pKas for enolate anion formation are 6.19, 9.94 and 9.44 for the keto tautomers and 7.41, 7,66 and 7.53 for the enols.The measurements demonstrate the effectiveness of the fluorenyl group in increassing enol stability and ketone acidity.For 9-formyfluorene, for which the enol is the stable tautomer, KE is increased by a factor of more than 107 and the acidity of the keto tautomer by more than 109 relative to acetaldehyde (pKE=6.17, pKa=16.73).For 9-acetyl- and 9-benzoyl-fluorenes tautomeric constants were determined kinetically by combining rate constants for ketonisation measured spectrophotometrically following quenching of their enolate anions in carboxylic acid buffers with rate constants for enolisation measured by halogen trapping under the same conditions.For 9-formylfluorene rate constants for enolisation were measured by generating its unstable aldehyde tautomer from an ethanethiol hemithioacetal by reaction with iodine.Combining these rate constants with rate constants for ketonisation from trapping the aldehyde with bisulfite ion gave the tautomeric constant.In aqueous solution the aldehyde tautomer of 9-formyfluorene is appreciably hydrated and an equilibrium constant Kh=/=5.6 was derived from measurements of the (slower) equilibration of enol and hydrate following enolisation in acetic acid buffers.In aqueous solution therefore the enol (71percent) and hydrate (24percent) are the principal species. log k-pH profiles for enolisation, ketonisation and hydration reactions are reported.Intrinsic reactivities of the three enolate anions towards protonation by H3O+ and carboxylic acids are comapred within and extended Broensted plot of log k versus ΔpK with mearurements by Kresge for the corresponding enolate anions derived from fluorene-9-carboxylic acid and its methyl, methylthio and methylthione esters.Surprisingly, not only are the thio and thione esters less acidic than the oxygen ester, but intrinsically less reactive.
Reactions of Carbanions with two Sterically Demanding 1-Benzoylaziridines: SET, SN2, Carbonyl Attack.
Bellos, Konstantinos,Stamm, Helmut
, p. 269 - 273 (2007/10/02)
Reactions of 2-phenyl (1a) and 2-benzyl (1b) 1-benzoyl-2-butylaziridines with carbanions X-, AH-, and Fl- of xanthene, dihydroanthracene and fluorene always form N-(2-butylethyl)-benzamides carrying phenyl (9a) or benzyl (9b).This reductive ring opening indicates an SET mechanism with aziridino ketyls 6a,b as intermediates.Nucleophilic ring opening (SNs) is found only with the carbanion of the lowest reducing power: Fl- 5a,b (62percent, 14percent).These two mechanisms cleave different bonds, a finding without precedence in SN2/SET competitions.Carbonyl addition resulting in benzoyl transfer to xanthene, dihydroanthracene or fluorene is usually also observed.It is the main reaction with X- and 1a.The highest yields of 9a,b are obtained with AH- since a special inner-sphere SET is available.
Novel Deoxygenative Acylation of Diaryl Ketones with Acylsilanes Mediated by Lanthanoid Metals
Taniguchi, Yuki,Nagafuji, Akihiro,Makioka, Yoshikazu,Takaki, Ken,Fujiwara, Yuzo
, p. 6897 - 6898 (2007/10/02)
The reaction of diaryl ketones and benzoyltrimethylsilane is mediated by lanthanoid metals such as ytterbium to give the deoxygenatively acylated product, 1,1-diarylacetophenones in good yields.In the reaction with acetylsilane, the corresponding silyl enol ether was obtained in a moderate yield.
Trifluoromethanesulfonic (Triflic) Acid Catalyzed Transformations of α-Hydroxy Carbonyl Compounds
Olah, George A.,Wu, An-hsiang
, p. 2531 - 2534 (2007/10/02)
Triflic acid catalyzed reaction of 2-hydroxy-2-adamantanecarboxylic acid results via ionizative decarbonylation in the formation of adamantanone.Under carbon monoxide pressure pinacol-type rearrangement gives 4,5-homoadamantanedione.Reactions of a series of α-hydroxy ketones result in fragmentation, deprotonation, and cyclization, respectively.The reactions and their suggested mechanism are discussed.
Studies in the Cycloproparene Series: On the Polarity of Alkylidenecycloproparenes
Halton, Brian,Buckland, Simon J.,Lu, Qi,Mei, Qiu,Stang, Peter J.
, p. 2418 - 2422 (2007/10/02)
Permanent dipole moments of the alkylidenecycloproparenes 4-6, 8-10, and 14 fall in the range 0.4-2.6 D.The data confirm polarity in these compounds to an extent that is dependent upon the nature of the substituents attached to the exocyclic double bond.T
Enol Content of α-Pyridyl- and Pyridinio-acetophenones
Carey, A. R. Edwin,Al-Quatami, Shaikha,O'Ferrall, Rory A. More,Murray, Brian A.
, p. 1097 - 1098 (2007/10/02)
A comparison of the effects of phenyl, pyridyl, and pyridinio substituents upon keto-enol tautomerisation and enol ionisation equilibria of acetophenone shows that polar effects upon bond hybridisation and resonance interaction with 'neutral' double bonds are important influences upon enol stability.
The Oxiren-Oxo Carbene Interconversion from a More Preparative Point of View
Ruehl, Wolfgang,Boelsing, Friedrich,Hofer, Edgar,Speer, Dietrich,Jansen, Martin
, p. 772 - 775 (2007/10/02)
The photochemical decomposition of α-diazoketone 1 in toluene gives rise to the formation of the well known keto carbene-oxirene equilibrium from which not only the product of the Wolff rearrangement can be derived but also the compounds 5, 6 and 7 which
