[PhLiNCH2CH2NLiPh]·3 HMPA, ein monomeres Dilithiumethylendiamid mit N2Li2‐Doppelüberbrückung: Synthese, Kristallstruktur und MO‐Rechnungen

Armstrong, David R.; Barr, David P.; Brooker, Alan T.; Clegg, William; Gregory, Karina; Hodgson, Susan M.; Snaith, Ronald; Wright, Dominic S.

doi:10.1002/ange.19901020432

Cited by 17 publications

(12 citation statements)

References 12 publications

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“…one side of the LÍ2N2 ring. 19 This structural motif was found for the crystal structure of the hexamethylphosphoramide (HMPA) adduct19 [(CH2NPh)2LÍ2(HMPA)3]. In forming a dilithium-bridged species, the geometry of the unsolvated monomeric unit of a dilithiated ethylenediamine would have to change very little to allow for the stacking of two of these units.…”

Section: Discussionmentioning

confidence: 90%

Carbolithiations of N,N'-Di-tert-butyl-1,4-diazabuta-1,3-diene

Gardiner¹,

Raston²

1995

Inorg. Chem.

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Section: Discussionmentioning

confidence: 90%

Carbolithiations of N,N'-Di-tert-butyl-1,4-diazabuta-1,3-diene

Gardiner¹,

Raston²

1995

Inorg. Chem.

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“…In place of the amide groups of the hexa‐1,5‐diene‐1,6‐diamide brackets of 5 two THF molecules are coordinated to the lithium atoms with a third molecule of THF additionally bridging the two alkali metals 6. 15 Notably, the characteristic interaction between the lithium atom Li2 and the π‐electron system of the phenyl group remains the same as in 5 (Li2C5 2.395(5), Li2C10 2.363(6) Å). Considering the line‐broadening and the striking high‐field shift of the 1 H and 13 C NMR signals of the phenyl group in the NMR spectra of 6 (Table 1) it becomes evident that this contact is not broken even by the donor solvent THF.…”

Section: Methodsmentioning

confidence: 88%

Reduction of a 1‐Aza‐1,3‐diene to a 1‐Azabut‐2‐ene‐1,4‐diyl Dianion: An Unusual Reaction Course

2003

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We have been searching for a rather simple method for the synthesis of 1-aza-1,3-diene complexes of early transition metals for quite some time. This search is motivated by some remarkable applications of these compounds: For example, (1-aza-1,3-diene)zirconocene complexes react diastereoselectively with carbonyl compounds to form seven-membered zirconacycles, [1a] from which highly substituted five-membered oxygen heterocycles, which are applied in the synthesis of natural products and active agents, can be separated.[1b]Titanium 1-aza-1,3-diene complexes in turn offer a simple approach to novel metallacyclic alkylidene complexes. For example, in attempts to methylate (1-aza-1,3-diene)titanium complexes even under mild conditions, an a-agostic Ti ! HÀC interaction on the terminal methine group of the 1-aza-1,3-diene ligand triggers an a-methane elimination that results in

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“…[2a,c] For our vicinal secondary amine systems, we support the suggestion of Gibson et al that reactions involving 1 or 2 proceed via a reactive bislithium amide structure. [8] The doubly bridged N 2 Li 2 arrangement has been observed for this type of structure, [18] which we would expect to be highly activating toward a coordinated carbonyl moiety (Scheme 2). [19,20] This proposal, like Gibsons observations, mentioned above, requires "a ready exchange of lithium cations between all the nitrogen sites in the system".…”

Section: Angewandte Chemiementioning

confidence: 92%

Chiral Bases as Useful Probes of Lithium Amide Reactivity

Prestly¹,

Simpkins²

2012

Angew Chem Int Ed

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Lithium amides are indispensable as strong bases in organic synthesis, particularly for the generation of metal enolates from compounds that possess C = O functions of all types. [1] These reagents exhibit complex structural behavior, particularly in solution, in which the formation of aggregates and mixed aggregates is commonplace, leading to a mechanistically rich repertoire of enolization and metalation chemistry. [2] Our own interest in this area has focused on the use of chiral lithium amides in asymmetric lithiation processes. [3] One key finding in this regard is the exceptional levels of enantioselectivity that are frequently provided by lithium amide 1 and bislithium amide 2 (both derived from diamine 3), in diverse asymmetric metalation reactions (Scheme 1, Eq. (1)- (3)). [4] In the asymmetric alkylation of piperidine diester 4, the use of lithium bisamide 2 proved essential for attaining both optimal yield and asymmetric induction. [5] The explanation for the much cleaner reactions observed using this base compared to LDA and simpler chiral lithium amides was not clear. In the case of systems that are prone to overreaction, such as ring-fused imide 6, we found the use of the diamine motif as a monolithium amide preferable. [6]

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[PhLiNCH₂CH₂NLiPh]·3 HMPA, ein monomeres Dilithiumethylendiamid mit N₂Li₂‐Doppelüberbrückung: Synthese, Kristallstruktur und MO‐Rechnungen

Cited by 17 publications

References 12 publications

Carbolithiations of N,N'-Di-tert-butyl-1,4-diazabuta-1,3-diene

Carbolithiations of N,N'-Di-tert-butyl-1,4-diazabuta-1,3-diene

Reduction of a 1‐Aza‐1,3‐diene to a 1‐Azabut‐2‐ene‐1,4‐diyl Dianion: An Unusual Reaction Course

Chiral Bases as Useful Probes of Lithium Amide Reactivity

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