4176-69-6Relevant academic research and scientific papers
Which Factors Control the Nucleophilic Reactivities of Enamines?
Timofeeva, Daria S.,Mayer, Robert J.,Mayer, Peter,Ofial, Armin R.,Mayr, Herbert
, p. 5901 - 5910 (2018)
Changes in rate constants, equivalent to changes in Gibbs energies of activation ΔG≠, are commonly referred to as kinetic effects and differentiated from thermodynamic effects (ΔrG°). Often, little attention is paid to the fact that structural effects on ΔG≠ are composed of a thermodynamic (ΔrG°) and a truly kinetic (intrinsic) component (ΔG0≠), as expressed by the Marcus equation. Rate and equilibrium constants have been determined for a number of reactions of enamines with benzhydrylium ions (Aryl2CH+), which has allowed the determination of Marcus intrinsic barriers and a differentiated analysis of structure–reactivity relationships. To our knowledge, this is the first report in which the Lewis basicity of a πCC bond towards carbon-centered Lewis acids (for example, carbenium ions) has quantitatively been determined. The synthesis, structures, and properties of deoxybenzoin-derived enamines ArCH=C(Ph)NR2, which have been designed as reference nucleophiles for the future quantification of electrophilic reactivities, are explicitly described.
Alkali metal and stoichiometric effects in intermolecular hydroamination catalysed by lithium, sodium and potassium magnesiates
Davin, Laia,Hernán-Gómez, Alberto,McLaughlin, Calum,Kennedy, Alan R.,McLellan, Ross,Hevia, Eva
, p. 8122 - 8130 (2019/06/18)
Main group bimetallic complexes, while being increasingly used in stoichiometric deprotonation and metal-halogen exchange reactions, have not yet made a significant impact in catalytic applications. This paper explores the ability of alkali metal magnesiates to catalyse the intermolecular hydroamination of alkynes and alkenes using sytrene and diphenylacetylene as principle setting model substrates. By systematically studying the role of the alkali-metal and the formulation of the heterobimetallic precatalyst, this study establishes higher order potassium magnesiate [(PMDETA)2K2Mg(CH2SiMe3)4] (7) as a highly effective system capable of catalysing hydroamination of styrene and diphenylacetylene with several amines while operating at room temperature. This high reactivity contrasts with the complete lack of catalytic ability of neutral Mg(CH2SiMe3)2, even when harsher reaction conditions are employed (24 h, 80 °C). A pronounced alkali metal effect is also uncovered proving that the alkali metal (Li, Na, or K) is not a mere spectating counterion. Through stoichiometric reactions, and structural and spectroscopic (DOSY NMR) investigations we shed some light on the potential reaction pathway as well as the constitution of key intermediates. This work suggests that the enhanced catalytic activity of 7 can be rationalised in terms of the superior nucleophilic power of the formally dianionic magnesiate {Mg(NR2)4}2- generated in situ during the hydroamination process, along with the ability of potassium to engage in π-interactions with the unsaturated organic substrate, enhancing its susceptibility towards a nucleophilic attack by the amide anion.
Stereo- and regioselective gold-catalyzed hydroamination of internal alkynes with dialkylamines
Hesp, Kevin D.,Stradiotto, Mark
supporting information; experimental part, p. 18026 - 18029 (2011/03/16)
We report the use of a P,N-ligand to support a gold complex as a state-of-the-art precatalyst for the stereoselective hydroamination of internal aryl alkynes with dialkylamines to afford E-enamine products. Substrates featuring a diverse range of functional groups on both the amine (ether, sulfide, N-Boc amine, fluoro, nitrile, nitro, alcohol, N-heterocycles, amide, ester, and carboxylic acid) and alkyne (ether, N-heterocycles, N-phthalimide amines, and silyl ethers) are accommodated with synthetically useful regioselectivity.
Broadening the scope of group 4 hydroamination catalysis using a tethered ureate ligand
Leitch, David C.,Payne, Philippa R.,Dunbar, Christine R.,Schafer, Laurel L.
supporting information; experimental part, p. 18246 - 18247 (2010/04/25)
(Chemical Equation Presented) A broadly applicable group-4-based precatalyst for the hydroamination of primary and secondary amines was developed. Screening experiments involving a series of amide and urea proligands led to the discovery of a tethered bis(ureate) zirconium complex with unprecedented reactivity in the intermolecular hydroamination of alkynes and the intramolecular hydroamination of alkenes. This catalyst system is effective with primary and secondary amines, 1,2-disubstituted alkenes, and heteroatom-containing functional groups, including ethers, silanes, amines, and heteroaromatics. The gem-disubstituent effect is not required for cyclization. The catalyst is generally regioselective for the anti-Markovnikov product of intermolecular alkyne hydroamination, and chemoselective for hydroamination over C-alkylation when forming 6- and 7-membered rings from aminoalkenes.
Studies on dioxirane chemoselectivity: The oxidation of an enamino moiety present in a Fischer carbene complex
Lluch, Anna-Maria,Gibert, Mariona,Sanchez-Baeza, Francisco,Messeguer, Angel
, p. 3973 - 3982 (2007/10/03)
The dimethyldioxirane (DMD) promoted oxidative decomplexation of Fischer carbene complex 1, which contains a conjugated enamino moiety, was investigted. Thus, treatment of 1 with 3 molecular equivalents of DMD afforded a 52% yield of amide 3 as unique isolable organic product. When the reaction was performed with 1 molecular equivalent of DMD the formation of the enol intermediate 15 was evidenced by its capture as the tetrafluoroboric acid salt 16. This salt was unstable and when it was exposed to air gave rise to amide 3 and to low amounts of ethyl benzoate and acetophenone. These results indicate that the presence of an enamino group conjugated to the Fischer carbene moiety inverts the chemoselectivity previously observed in the DMD promoted decomplexation of these compounds. Thus, the major pathway involves the oxidation of the enamino double bond through the formation of an enol intermediate which reacts with oxygen to give products resulting from the breakdown of the molecule.
Enamine synthesis using the Horner-Wittig reaction. Part 2. New acyl anion equivalents derived from (aminomethyl)diphenylphosphine oxides
Broekhof, N. L. J. M.,Elburg, P. van,Hoff, D. J.,Gen, A. van der
, p. 317 - 321 (2007/10/02)
Using the Horner-Wittig reagents (1-morpholino-alkyl)diphenylphosphine oxides (1), aromatic as well as aliphatic α,β-unsaturated aldehydes can be converted into the morpholino enamines of their respective homologous phenyl, ethyl and styryl ketones.These enamines can be easily converted into the corresponding ketones by mild, acid-catalyzed hydrolysis.The usefulness of these phosphine oxides as acyl anion equivalents is further demonstrated by the synthesis of dihydrojasmone and of (Z)-6-henicosen-11-one.
