A chiral reagent inducing asymmetry in electrophilic amination reactions

The chiral amination reagent (?)-$\text{1}$ was prepared from (?)-ephedrine, configurationally determined by X-ray structure analysis and reacted with carbon nucleophiles to yield the optically active amines $\text{4a-d}$ with up to 44% ee.     

Asymmetric electrophilic amination of various carbon nucleophiles with enantiomerically pure chiral N-h oxaziridines derived from camphor and fenchone

The first two stable enantiomerically pure chiral N-H oxaziridines, derived from camphor and fenchone, are shown to act as electrophilic sources of nitrogen upon reaction with various carbon nucleophiles. Nitrogen is transferred, together with the camphor/fenchone unit, when deprotonated esters, malonates, and nitriles are used as nucleophiles. One of the ester or nitrile units in the substrate usually undergoes hydrolysis; a cyclic mechanism is proposed to account for this observation.     

Synthesis of alpha-hydrazino ketones via regio- and stereoselective electrophilic amination of manganese enolates and enamines

A straightforward procedure for the regio- and stereoselective synthesis of alpha-hydrazino ketones is described. Manganese enolates and manganese enamines derived from ketones and from the corresponding N-sulfinylimines react with azodicarboxylate esters (DTBAD and DEAD) in a regioselective fashion to afford in good to excellent yields the kinetic alpha-hydrazino ketones as sole or highly prevalent products. When enantiopure N-sulfinyl manganese enamines were used the stereoselectivity of these reactions ranged from 40% to 68% ee.     

Asymmetric protonation of ketone enolates using chiral beta-hydroxyethers: acidity-tuned enantioselectivity

New chiral hydroxyethers 1a-f were prepared for asymmetric protonation of achiral enolates prepared from prochiral ketones. The enantioselectivity of protonation was highly dependent upon the acidity of the chiral alcohols, the highest enantioselectivity (90% ee) being achieved with 3,5-dichloro-substituted beta-hydroxyether 1c. A salt-free enolate generated from trimethylsilyl enol ether 4 provided product of the highest ee. Unlike other reagents, chloro-substituted alcohols provided almost consistent enantioselections throughout the reaction temperatures examined (-25 to -98 degrees C). Protonation of other aromatic ketones showed selectivity similar to that of 2-methyl-1-tetralone.     

Asymmetric amination of butadiene by secondary amines,catalyzed-by low-valence nickel chiral complexes

Conclusions It was shown that it is theoretically possible to obtain optically active unsaturated amines by reacting butadiene with the simpler secondary amines in the presence of chiral Ni-containing metal complex catalysts.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2771–2777, December, 1980.     

Asymmetric allylic amination in water catalyzed by an amphiphilic resin-supported chiral palladium complex

[reaction: see text] Catalytic asymmetric allylic amination of cycloalkenyl carbonates (methyl cyclohexen-2-yl carbonate, methyl cyclohepten-2-yl carbonate, methyl 5-methoxycarbonylcyclohexen-2-yl carbonate, methyl cyclohexenyl carbonate, tert-butyl 5-methoxycarbonyloxy-1,2,5,6-tetrahydropyridinedicarboxylate) with dibenzylamines ((C6H5CH2)2NH, (C6H5CH2)(4-CH3OC6H4CH2)NH, (4-CH3OC6H4CH2)2NH) was achieved in water under heterogeneous conditions by use of a palladium complex of (3R,9aS)-3-[2-(diphenylphosphino)phenyl]-2-phenyltetrahydro-1H-imidazo[1,5-a]indole-1-one anchored on polystyrene-poly(ethylene glycol) copolymer resin to give the corresponding cycloalkenylamines with high enantiomeric selectivity (90-98% ee).     

Transition-metal-free electrophilic amination of arylboroxines

A transition-metal-free strategy to construct C(sp(2))-N bonds using arylboroxines and O-benzoyl hydroxylamines as coupling partners has been developed. This transformation provides a useful method to access various aromatic amines.     

Asymmetric alkylation and sulphenylation of chiral O-silylated imide enolates.

The chiral O-silylated enolates (5) can be alkylated or sulphenylated with high diastereoselectivity (～20:1) by 1,3-dithienium fluoroborate or PhSCl. Phenylthio-alkylation, in contrast, proceeds with low diastereoselectivity.     

Copper-catalyzed electrophilic amination of diorganozinc reagents

The copper-catalyzed electrophilic amination of diorganozinc reagents employing O-acyl N,N-dialkyl hydroxylamine derivatives as aminating agents is described. This reaction offers a general method for the preparation of tertiary amines in high yields and is noteworthy for its convenience both in terms of reaction conditions employed (room temperature, 相似文献   

Enantioselective alkylation of chiral enolates

Alkylations of chiral amide enolates derived from (?)-prolinol have been shown to yield versatile hydroxy-amides in high diastereomeric purity. Their use in the preparation of optically active carboxylic acids is described.     

Copper-catalyzed electrophilic amination of functionalized diarylzinc reagents

The copper-catalyzed electrophilic amination of functionalized diarylzinc reagents with O-acyl hydroxylamines allows for the preparation of functionalized tertiary arylamines in high yields, and is noteworthy for the mild reaction conditions employed. The functionalized diarylzinc reagents were prepared via an iodine/magnesium exchange of the corresponding aryl iodide followed by transmetalation of the resultant Grignard species with ZnCl(2).     

Comparison of electrophilic amination reagents for N-amination of 2-oxazolidinones and application to synthesis of chiral hydrazones

Comparison of several hydroxylamine-based electrophilic ammonia equivalents in the N-amination of 2-oxazolidinones revealed that O-(p-nitrobenzoyl)hydroxylamine (NbzONH(2)) and sodium hydride in dioxane is a superior reagent combination for this purpose. Practical preparations of a variety of chiral N-acylhydrazones by this method gave yields ranging from 45 to 95%. Methods for exchange or removal of the aldehyde component have been developed, making this a general route to chiral N-acylhydrazones of interest for asymmetric synthesis applications.     

Reagents for electrophilic amination: a quantum Monte Carlo study

Electrophilic amination is an appealing synthetic strategy to construct carbon-nitrogen bonds. The authors explore the use of the quantum Monte Carlo method and a proposed variant of the electron pair localization function--the electron pair localization function density--as a measure of the nucleophilicity of nitrogen lone pairs as a possible screening procedure for electrophilic reagents.     

Improved reagent for electrophilic amination of stabilized carbanions

[reaction: see text]. Enolate amination using O-di(p-methoxyphenyl)phosphinylhydroxylamine 2 is reported. Reagent 2 reacts efficiently with stabilized sodium or potassium enolates derived from malonates, phenylacetates, and phenylacetonitriles and is sufficiently soluble for use in solution at -78 degrees C.     

Chiral calcium organophosphate-catalyzed enantioselective electrophilic amination of enamides

Highly enantioselective direct amination of enamides catalyzed by chiral nonracemic calcium bis(phosphate) complex 3g afforded optically active 1,2-hydrazinoimines 4. Following a subsequent in situ hydrolysis or reduction, 2-hydrazinoketones 5 or syn-1,2-disubstituted 1,2-diamines 6 were obtained in high yields and excellent enantiomeric excess.     

Asymmetric synthesis of 3,5-bis(isopropyloxy)-4-methoxyphenyl glycine by way of a diastereoselective Strecker reaction and an Evans electrophilic amination reaction

Two short syntheses of D-N-Boc-3,5-bis(isopropyloxy)-4-methoxyphenyl glycine, a central unit of vancomycin type antibiotics, have been developed. A diastereoselective Strecker reaction using (S)-phenylglycinol as a chiral inducer was the key step in the first synthesis, while Evans' electrophilic amination technology was employed for introducing both the amino function and the chirality in the second strategy.     

Axially chiral guanidine as highly active and enantioselective catalyst for electrophilic amination of unsymmetrically substituted 1,3-dicarbonyl compounds

A newly designed axially chiral guanidine is found to function as an effective platform for asymmetric induction at the alpha-carbon of unsymmetrically substituted 1,3-dicarbonyl compounds. Highly efficient and enantioselective electrophilic amination of various 1,3-dicarbonyl compounds with azodicarboxylate was successfully achieved using the present chiral guanidine catalyst, which provides efficient access to the construction of nitrogen-substituted quaternary stereocenters in an optically active form.     

Asymmetric aziridine synthesis by aza-Darzens reaction of N-diphenylphosphinylimines with chiral enolates. Part 2: Inversion of diastereoselectivity

The aza-Darzens (‘ADZ’) reactions of N-diphenylphosphinyl (‘N-Dpp’) imines with chiral enolates derived from N-bromoacetyl 2S-2,10-camphorsultam proceed in generally good yield to give N-diphenylphosphinyl aziridinoyl sultams. However, the stereoselectivity of the reaction is dependent upon the structure of the imine substituent: when the chiral enolate was reacted with arylimines substituted in the ortho-position, mixtures of cis- and trans-2′R,3′R-aziridines were obtained, often with a complete selectivity in favour of the trans-isomer.