5384-63-4Relevant articles and documents
Facile Reversible Benzophenone Insertion into Rare-Earth Metal Pyrazolate Complexes
Werner, Daniel,Deacon, Glen B.,Junk, Peter C.,Anwander, Reiner
, p. 3419 - 3428 (2017)
Treatment of the homoleptic CeIV pyrazolate complex [Ce(Me2pz)4]2 (Me2pz = 3,5-dimethylpyrazolato) with benzophenone (bp) led to the formation of an Me2pz-substituted diphenylmethoxy-(N,O)-chelating ligand (pdpm), possibly metal-templated through initial coordination of bp to the cerium atom and subsequent bp insertion into the Ce–N(Me2pz) bond. This coordination/insertion process was shown to be reversible, leading to a complex sequence of equilibria involving multiple degrees of insertion/de-insertion and association/dissociation. The dependency on temperature and the amount of bp of all equilibria was revealed, with insertion/association of bp being favored at low temperatures and de-insertion/dissociation preferentially occurring at elevated temperatures. Such sets of equilibria were also observed for the treatment of trivalent complexes [Ln(Me2pz)3(thf)]2 (Ln = La, Ce, Lu) with bp. Through structural analysis, the trivalent complexes were shown to be less effective in the bp-to-pdpm conversion than the CeIV derivative, giving direct evidence of how an increase in rare-earth Lewis acidity aids in ketone anchorage and concomitant conversion. The observed equilibria seem to also apply to the more illustrious organocerium systems. The conversion of bp into the corresponding tertiary alcohol by the routinely employed reagent CeCl3/nBuLi is the most selective when termination of the reaction by hydrolysis is performed at lower temperatures, with a reagent ratio bp/CeCl3/nBuLi of 1:1:1.
I-Pr2NMgCl·LiCl Enables the Synthesis of Ketones by Direct Addition of Grignard Reagents to Carboxylate Anions
Colas, Kilian,Dos Santos, A. Catarina V. D.,Mendoza, Abraham
supporting information, (2019/10/08)
The direct preparation of ketones from carboxylate anions is greatly limited by the required use of organolithium reagents or activated acyl sources that need to be independently prepared. Herein, a specific magnesium amide additive is used to activate and control the addition of more tolerant Grignard reagents to carboxylate anions. This strategy enables the modular synthesis of ketones from CO2 and the preparation of isotopically labeled pharmaceutical building blocks in a single operation.
Introducing deep eutectic solvents to polar organometallic chemistry: Chemoselective addition of organolithium and grignard reagents to ketones in air
Vidal, Cristian,Garcia-Alvarez, Joaquin,Hernan-Gomez, Alberto,Kennedy, Alan R.,Hevia, Eva
supporting information, p. 5969 - 5973 (2014/06/10)
Despite their enormous synthetic relevance, the use of polar organolithium and Grignard reagents is greatly limited by their requirements of low temperatures in order to control their reactivity as well as the need of dry organic solvents and inert atmosphere protocols to avoid their fast decomposition. Breaking new ground on the applications of these commodity organometallics in synthesis under more environmentally friendly conditions, this work introduces deep eutetic solvents (DESs) as a green alternative media to carry out chemoselective additions of ketones in air at room temperature. Comparing their reactivities in DES with those observed in pure water suggest that a kinetic activation of the alkylating reagents is taking place, favoring nucleophilic addition over the competitive hydrolysis, which can be rationalized through formation of halide-rich magnesiate or lithiate species. Turning lithium green: A new protocol for the selective addition of Grignard and organolithium reagents to ketones in green, biorenewable, and deep eutectic solvents (DESs) is reported. The protocol establishes a bridge between main-group organometallic compounds and green solvents (ChCl=choline chloride; see picture). The DESs are superior reaction media for highly polar organometallic compounds.
