Carbanions of Alkali and Alkaline Earth Cations: (i) Synthesis and Structural Characterization

Lithium Enolates Derived from Pyroglutaminol: Aggregation, Solvation, and Atropisomerism

“…It would be reasonable to infer from crystallographic and computational evidence that the enolate tetramers are tetrasolvated, as in 8 (Scheme ), but partial solvates have been observed in tetramers comprising hindered enolates . To demonstrate qualitatively the existence of solvation, we turned to pyridine as a chemical shift reagent .…”

“…The appeal of the pyroglutaminol-derived skeleton is that the hemiaminal linkage can be varied without perturbing the core γ-lactam moiety. Moreover, the enolate geometries are necessarily E , and the chirality provides a means to correlate mechanism and reactivity with stereochemistry. , …”

Catalytic Carbon–Carbon Bond‐Forming Reactions of Weakly Acidic Carbon Pronucleophiles Using Strong Brønsted Bases as Catalysts

“…However,l arge amountso fr eagents are typicallyr equired to form the reactive carbanion species. For example, more than one equivalent of strong base (e.g.,l ithium diisopropylamide (LDA) or n-butyllithium (nBuLi)) is required for deprotonation, [2] or stoichiometric amounts of reagents are required to modify the starting substrates to am ore reactive form (e.g.,f ormation of Grignard reagents from alkyl halides). [3] This is as ignificant problem from the viewpoint of atom economy.…”

Selective Meta‐Deprotonation of Toluene by Using Alkali‐Metal‐Mediated Magnesiation

“…Owing largely to their polar nature, alkali-metal alkyl ("RM") and amide ("R 2 NM") compounds, especially those of lithium, are often the best reagents for effecting deprotonative metalation, but there are limits to their selectivity. [2,3] A primary source of aromatic compounds, alkylbenzenes, typified by toluene, offer several sites for metalation: the alkyl side chain or the ortho, meta, or para ring sites. [4] However, in practice, toluene is almost exclusively metalated on the CH 3 substituent by common reagents such as BuLi-(tmeda) (tmeda is N,N,N',N'-tetramethylethylenediamine), BuNa, or BuK.…”