Synthesis and Structure of a Monomeric Chiral Lithium Dialkylaluminium Amide Derived from Schöllkopf’s Bis‐lactim Ether and α‐(Methylbenzyl)benzylamine

Andrews, Philip C.; Maguire, Melissa; Pombo‐Villar, Esteban

doi:10.1002/ejic.200300186

Cited by 4 publications

(1 citation statement)

References 28 publications

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“…Prompted by the low stereoselectivity achieved in the azaenolate additions to the mismatched threose acetonides, we tested the process in the presence of other metallic counterions. Thus, we prepared the zinc(II), aluminum(III), and the titanium(IV) azaenolates from Li + 15 - and ZnCl 2 , Et 2 AlCl, or Ti(O i Pr) 3 Cl (at −78 °C in THF), but their additions to the acetonides 13a or 13b also proceeded with low stereoselectivity and led to mixtures of the three adducts 16/17/18 with 40:42:18, 53:29:18 and 49:41:10 ratios, respectively. All mixtures of benzylated, silylated, or “unprotected” aldol products were separated by flash chromatography, and thus adducts 16a − c and 17a − c could be isolated as single diastereoisomers in 31−44% and 28−31% yield, respectively.…”

Section: Resultsmentioning

confidence: 99%

Diastereoselective Synthesis of Piperidine Imino Sugars Using Aldol Additions of Metalated Bislactim Ethers to Threose and Erythrose Acetonides

et al. 2008

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A general strategy for the synthesis of 1-deoxy-azasugars from a chiral glycine equivalent and 4-carbon building blocks is described. Diastereoselective aldol additions of metalated bislactim ethers to matched and mismatched erythrose or threose acetonides and intramolecular N-alkylation (by reductive amination or nucleophilic substitution) were used as key steps. The dependence of the yield and the asymmetric induction of the aldol addition with the nature of the metallic counterion of the azaenolate and the gamma-alkoxy protecting group for the erythrose or threose acetonides has been studied. The stereochemical outcome of the aldol additions with tin(II) azaenolates has been rationalized with the aid of density functional theory (DFT) calculations. In accordance with DFT calculations with model glyceraldehyde acetonides, high trans,syn,anti-selectivitity for the matched pairs and moderate to low trans,anti,anti-selectivity for the mismatched ones may originate from (1) the intervention of solvated aggregates of tin(II) azaenolate and lithium chloride as the reactive species and (2) favored chair-like transition structures with a Cornforth-like conformation for the aldehyde moiety. DFT calculations indicate that aldol additions to erythrose acetonides proceed by an initial deprotonation, followed by coordination of the alkoxy-derivative to the tin(II) azaenolate and final reorganization of the intermediate complex through pericyclic transition structures in which the erythrose moiety is involved in a seven-membered chelate ring. The preparative utility of the aldol-based approach was demonstrated by application in concise routes for the synthesis of the glycosidase inhibitors 1-deoxy-d-allonojirimycin, 1-deoxy-L-altronojirimycin, 1-deoxy-D-gulonojirimycin, 1-deoxy-D-galactonojirimycin, 1-deoxy-L-idonojirimycin and 1-deoxy-D-talonojirimycin.

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Section: Resultsmentioning

confidence: 99%

Diastereoselective Synthesis of Piperidine Imino Sugars Using Aldol Additions of Metalated Bislactim Ethers to Threose and Erythrose Acetonides

et al. 2008

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Formal Oxidation State +3: Organometallic Chemistry

Aldridge

Downs

Kays

2011

The Group 13 Metals Aluminium, Gallium, Indium and Thallium: Chemical Patterns and Peculiarities

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Donor‐influenced Structure–Activity Correlations in Stoichiometric and Catalytic Reactions of Lithium Monoamido‐Monohydrido‐Dialkylaluminates

Lemmerz

McLellan

Judge

et al. 2018

Chemistry A European J

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A series of heteroleptic monoamido‐monohydrido‐dialkylaluminate complexes of general formula [iBu2AlTMPHLi⋅donor] were synthesized and characterised in solution and in the solid state. Applying these complexes in catalytic hydroboration reactions with representative aldehydes and ketones reveals that all are competent, however a definite donor substituent effect is discernible. The bifunctional nature of the complexes is also probed by assessing their performance in metallation of a triazole and phenylacetylene and addition across pyrazine. These results lead to an example of phenylacetylene hydroboration, which likely proceeds via deprotonation, rather than insertion as observed with the aldehydes and ketones. Collectively, the results emphasise that reactivity is strongly influenced by both the mixed‐metal constitution and mixed‐ligand constitution of the new aluminates.

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Synthesis and Structure of a Monomeric Chiral Lithium Dialkylaluminium Amide Derived from Schöllkopf’s Bis‐lactim Ether and α‐(Methylbenzyl)benzylamine

Cited by 4 publications

References 28 publications

Diastereoselective Synthesis of Piperidine Imino Sugars Using Aldol Additions of Metalated Bislactim Ethers to Threose and Erythrose Acetonides

Diastereoselective Synthesis of Piperidine Imino Sugars Using Aldol Additions of Metalated Bislactim Ethers to Threose and Erythrose Acetonides

Formal Oxidation State +3: Organometallic Chemistry

Donor‐influenced Structure–Activity Correlations in Stoichiometric and Catalytic Reactions of Lithium Monoamido‐Monohydrido‐Dialkylaluminates

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