4176-68-5Relevant academic research and scientific papers
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.
New reaction of enamines with aryldiazoacetates catalyzed by transition metal complexes
Zhao, Wei-Jie,Yan, Ming,Huang, Dan,Ji, Shun-Jun
, p. 5585 - 5593 (2007/10/03)
The reaction of aryldiazoacetates with enamines catalyzed by copper and rhodium complexes provided γ-keto esters in good yields. A full investigation of the effects of solvents, catalysts, enamines and aryldiazoacetates on the reaction was carried out. Careful analysis of the crude reaction mixture revealed a substituted enamine as the primary product, which was hydrolyzed over silica gel to give a γ-keto ester as the final product. A reaction mechanism involving nucleophilic addition of an enamine to a metal carbene and subsequent hydrogen transfer was proposed. Chiral dirhodium and copper catalysts were examined and found to provide γ-keto esters with no enantioselectivity. The result could be rationalized based on the proposed reaction mechanism. Attempts to trap the enamine intermediate with several electrophilic reagents were not successful.
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.
