Oxiranyl Anions and Aziridinyl Anions

Satoh, Tsuyoshi

doi:10.1021/cr950081v

Cited by 240 publications

(76 citation statements)

References 107 publications

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“…[1][2][3][4][5] In particular, the metal salts of diisopropylamine [da(H)], 1,1,1,3,3,3-hexamethyldisilazane [hmds(H)] and 2,2,6,6-tetramethylpiperidine [tmp(H)] are widely utilised across synthetic laboratories primarily because of the desirable combination of high Brønsted basicity and low nucleophilicity. Of particular interest in this study, another amido reagent, the thermally highly stable lithium diphenylamide (LiNPh 2 ), has shown promise in a range of synthetic transformations.…”

Section: Introductionmentioning

confidence: 99%

Structural Elucidation of tmeda‐Solvated Alkali Metal Diphenylamide Complexes

et al. 2009

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Lithium, sodium and potassium salts of diphenylamine have been prepared by using a deprotonative route and characterised in both, solid state (by X‐ray crystallography) and solution (by NMR spectroscopic studies). In each case the metal atom's coordination sphere is completed by coordination to the synthetically important co‐ligand N,N,N′,N′‐tetramethylethylenediamine (tmeda). Complexes 1 and 2 [{(tmeda)M(NPh2)}2] (M = Li for 1, Na for 2) can be prepared by treating 1 mol.‐equiv. of the parent amine with an equimolar quantity of nBuM and tmeda in hexane solution. In the solid state, 1 and 2 are essentially isostructural, being dimeric with a four‐atom M–N–M–N framework. The coordination sphere of each M atom is completed by a bidentate tmeda molecule. Complex 3 [{(tmeda)3/2K(NPh2)}2] has been prepared in a similar way to 1 and 2 except that benzylpotassium has been utilised as the metallating agent. In addition, 4 mol‐equiv. of tmeda is required to fully solubilise the heavy alkali metal amide mixture. In the solid state, 3 exists as a polymeric array of dinuclear K–N–K–N rings. Akin to 1 and 2, the K atom is coordinated to a bidentate tmeda molecule; however, each K atom is also bound to another tmeda molecule that acts as a monodentate bridge, thus producing the coordination polymer. Crystalline 1 and 2 are soluble in C6D6; hence, NMR spectroscopic studies could be performed. These show that the solid‐state structure appears to stay intact in arene solution. On the other hand, 3 is not soluble in C6D6; so solution studies have been performed in [D8]thf. These studies reveal that 3 readily looses tmeda during in‐vacuo isolation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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Section: Introductionmentioning

confidence: 99%

Structural Elucidation of tmeda‐Solvated Alkali Metal Diphenylamide Complexes

et al. 2009

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“…The intermediate carbanions reacted more readily with the carbonyl groups of the substrates than with methyl iodide. So, in place of the expected amides or esters of methylaziridine-2-carboxylic acids, amides or esters of 2-aziridinylcarbonylaziridine-2-carboxylic acids were isolated.Keywords: aziridinyl ketones, esters and amides of aziridin-2-carboxylic acids, deprotonation.Esters and amides of aziridine-2-carboxylic acids are suitable starting materials for the preparation of derivatives of α-and β-amino acids after opening the aziridine ring [2,3]. Unlike other esters of α-amino acids, aziridine-2-carboxylates do not have a tendency to dimerize to form diketopiperazines.…”

mentioning

confidence: 99%

“…Esters and amides of aziridine-2-carboxylic acids are suitable starting materials for the preparation of derivatives of α-and β-amino acids after opening the aziridine ring [2,3]. Unlike other esters of α-amino acids, aziridine-2-carboxylates do not have a tendency to dimerize to form diketopiperazines.…”

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confidence: 99%

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Unnatural amino acids. 3. Aziridinyl ketones from esters and amides of aziridine-2-carboxylic acids

Shtrumfs

Hermane

Kalvinsh

et al. 2007

Chem Heterocycl Compd

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A series of N-substituted amides and esters of aziridine-2-carboxylic acids have been prepared and have been subjected to deprotonation with lithium diisopropylamide. The intermediate carbanions reacted more readily with the carbonyl groups of the substrates than with methyl iodide. So, in place of the expected amides or esters of methylaziridine-2-carboxylic acids, amides or esters of 2-aziridinylcarbonylaziridine-2-carboxylic acids were isolated.Keywords: aziridinyl ketones, esters and amides of aziridin-2-carboxylic acids, deprotonation.Esters and amides of aziridine-2-carboxylic acids are suitable starting materials for the preparation of derivatives of α-and β-amino acids after opening the aziridine ring [2,3]. Unlike other esters of α-amino acids, aziridine-2-carboxylates do not have a tendency to dimerize to form diketopiperazines. Our interest in esters and amides of aziridine-2-carboxylic acids is connected with the study of the conditions for deprotonation of the α-center of the aziridine ring to prepare sterically hindered cyclic unnatural α-amino acids, required for the synthesis of different derivatives of α-and β-amino acids.Deprotonation of esters of aziridine-2-carboxylic acid was first carried out by Seebach [4,5]. However isolation of the reaction products was unsuccessful. Only after moving to thiol esters was isolation of the products from the reactions with electrophiles successful [4]. In this paper [4]it was first postulated that carbanions were configurationally stable at low temperatures. In 1997 Vedejs published a paper on lithiated complexes of aziridines with BH 3 [6]. It was shown that the increased s-character of the CH bonds in the aziridine ring accelerated lithiation in position 2 of the aziridine ring, facilitating the reaction with electrophiles.The stability of carbanions in a series of esters of aziridine-2-carboxylic acids has been demonstrated recently [7,8]. A methoxymethyl protecting group on the aziridine nitrogen atom stabilizes the intermediate carbanion and permits the preparation of a series of 2-substituted esters of aziridine-2-carboxylic acids [8]. Alkylation of 3-substituted esters of 1-(diphenylmethyl)aziridine-2-carboxylic acids gave a mixture of 2-alkylated aziridines and diaziridinyl ketones [9].We have studied the deprotonation of derivatives of aziridine-2-carboxylic with different substituents in the aziridine ring to determine the limits of use of this reaction. As substituents we chose well known protecting groups which are readily removed after the reaction was completed. We have developed a method for synthesis of the 1-substituted dimethylamides of the aziridine-2-carboxylic acids 2a-c (scheme 1) required for this study.

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“…In many cases, when the deprotonation step is conducted with an alkyllithium compound, the intramolecular processes depicted above can be circumvented by another reaction, namely the intermolecular alkylative insertion into C−Li bonds (Scheme 60, path a). The resulting substituted β-lithio lithium alkoxide undergoes Li 2 Here again, all these reactions have been widely reviewed 5,25,41,228,231 and just general trends will be discussed here, with a special focus on the mechanisms. These mechanisms can involve a carbenoid rearrangement or a free carbene rearrangement.…”

Section: Electrophilic Reactions Of Lithiooxiranesmentioning

confidence: 99%