Regiochemical control of the ring opening of aziridines by means of chelating processes. 2. Synthesis and ring-opening reactions of aziridines derived from 5,6-dihydro-2H-pyran and of the diastereoisomeric cis- and trans-aziridines derived from 3-(benzyloxy)cyclohexene, 2-(benzyloxy)-3,6-dihydro-... (original) (raw)

The asymmetric synthesis of aziridines

Tetrahedron: Asymmetry, 1997

Introduction 2. Synthesis of aziridines 2.1. From amino alcohols 2.2 From epoxides 2.3. From alkenes 2.4. From azirines 2.5. From imines 2.6. Resolution 3. Concluding remarks Contents

Unexplored Nucleophilic Ring Opening of Aziridines

Molecules, 2010

The reactivity of dianions of carboxylic acids towards aziridines has been studied. Although, a similar reactivity to that of enolates from ketones, esters or amides has been observed, the method directly yields γ-aminoacids in one step. The method is complementary of previous results of enenediolate reactivity with other electrophiles. A comparative study with the reactivity of this enediolates with epoxides is included.

Enantioselective Preparation, Conformational Analysis and Absolute Configuration of Highly Substituted Aziridines

Chirality, 2015

The first example of organocatalytic aziridination reaction of α-substituted-α,βunsaturated ketones is presented. The reaction was found to be highly enantio-and diastereoselective, yielding N-tosylated aziridines. Low-temperature nuclear magnetic resonance (NMR) spectra allowed for the determination of the N-inversion barrier, that was found to be quite lower with respect to unsubstituted aziridines. A thorough conformational analysis supported by low-temperature NMR data allowed for the determination of the absolute configuration of the main stereoisomer by means of time-dependent Density Functional Theory simulation of the electronic circular dichroism spectra.

Expedient synthesis of substituted (S)-N-(?-methylbenzyl)aziridines

Chemical Communications, 2006

We report for the first time that after O-acylation the conjugate addition products of (S)-N-(a-methylbenzyl)hydroxylamine undergo an efficient diastereoselective 3-exo-tet ring-closure reaction affording 2-and 2,3-disubstituted-N-alkylaziridines in good to excellent yields.

A convenient synthesis of optically active 1H-aziridine-2-carboxylic acids (esters

Tetrahedron Letters, 1989

Optically active glycidic esters, prepared from allylic alcohols employing the Sharpless enoxidation. were treated with sodium azide. In a subseauent reaction with PPhl the azido alcohols thus obtained were converted into aziridine-2-carboxylic esters of high optical purity in good yields. Aziridine-2-carboxylic acids represent an interesting class of compounds since they may be. considered simultaneously as a-or B-amino acid derivatives. Little attention has been devoted so far to these carboxylic bE.e. ofepoxy alcohol. determinedfrom bxnvn optical rotations (entries a. e, g) or by 4W MHz 'H-NMR analysti of the Masher derivarive (entries b. c, dj. CDeterminedfrom brown optical rotation (entry g) or by 400 MHZ 'H.NUR analysis ofthe Masher derivative (entries a. b. c, d, GJ reaction medium, rhe oxazaphospholidines could be isolated. The compounds 6 were then subjected to a bulb-to-bulb distillation using a Kugelrohr apparatus, yielding the aziridinecarboxylic esters in moderate yields (method A) (entries a, e). When, however, the Staudinger reaction was performed in DMF or acetonitrile as the solvent, stirring at room temperature for 0.5 h followed by heating at about 80°C for a few hours afforded the aziridines in good yields without isolation of the intermediate oxazaphospholidines 4883 (method B) (entries b, c, d, f, g). The progress of the aziridine formation was monitored by TLC and infrared spectroscopy. Mixtures of isomeric azido alcohols were used for the Staudinger reaction. Method A permits only the use of rather small amounts of substrate and the distillation procedure is experimentally rather difficult. Method B is much preferred, since the reaction can be carried out on at least a 10 g scale without decomposition problems. The intermediate oxazaphospholidine derived from azido alcohol 5Ag was characterized by means of an X-ray diffraction analysis (figure 1). l5 This reveals that the epoxide opening with azide occurs with inversion of configuration. Thus after the Staudinger reaction we obtained a c&oxazaphospholidine from a truns-glycidic ester. All the oxazaphospholidines 6 showed a characteristic IR absorption near 3450 cm-' INH).

Highly regioselective ring-opening of trisubstituted aziridines by sulfur-stabilised carbanions

Chemical Communications, 2009

Melting points were determined using a Stuart Scientific SMP1 melting point apparatus and are uncorrected. Infrared spectra were recorded on a Mattson 5000 FTIR spectrometer and on a Perkin-Elmer Spectrum RX FT-IR System. Proton magnetic resonance (1 H NMR) and carbon magnetic resonance (13 C NMR) spectra were recorded in CDCl 3 unless otherwise stated on a Jeol GSX-270, a Bruker DRX-300, a Bruker AV-400 or a Bruker AV-500 spectrometer. Chemical shifts are in part per million (ppm) and are referenced relative to the residual proton-containing solvent (1 H NMR: 7.26 ppm for CDCl 3 ; 13 C NMR: 77.0 ppm for CDCl 3). The following abbreviations are used to indicate the multiplicities: s, singlet, bs, broad signal; d, doublet; t, triplet; m multiplet. Mass spectra (CI) were recorded using Micromass AutoSpec-Q, Micromass Platform II or Micromass AutoSpec Premier instruments. Elemental analyses were performed at the microanalytical laboratory of the London Metropolitan University. Analytical thin layer chromatography (TLC) was performed on pre-coated aluminium-backed Merck Kiesegel 60 F 254 plates. Visualisation was effected with ultraviolet light, potassium permanganate or vanillin as appropriate. Flash chromatography was performed using BDH (40-63 μm) silica gel unless otherwise stated. DMSO and CH 2 Cl 2 were distilled under nitrogen from CaH 2 prior to use. All other solvents were reagent-grade. Petrol refers to the fraction with bp 760 40-60 °C. All liquid reagents except HCl and Me 2 S were distilled prior to use. KOAc was oven-dried at 120 °C for several days prior to use. All other reagents were purchased from Aldrich, Fluka, Acros, Alfa Aesar Lancaster and used as such unless otherwise stated. Microwave reactions were performed using a Biotage Initiator instrument. (E)-4-(4-Methoxyphenyl)but-2-en-1-ol 1