A novel procedure for the synthesis of aziridines: application of Simmons–Smith reagents to aziridination (original) (raw)
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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.
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
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).
Tetrahedron Letters, 2000
InCl 3 catalyzed reactions of ethyl diazoacetate with aldimines give aziridine carboxylates under mild conditions, low catalyst loading and with high cis-selectivity. # Aziridines are useful building blocks for the synthesis of many biologically active compounds such as amino alcohols, unnatural amino acids and nitrogenous heterocycles. 1 In view of this, stereoselective synthesis of aziridines continues to attract the attention of synthetic chemists. In 1995, a conceptually new synthesis of aziridines via catalyzed carbene-transfer reactions of a-diazoacetates with imines, appeared in the literature. 2 Although copper(II) salts were seminally used as catalysts for these reactions, the yields and/or diastereoselectivities of aziridine formation were somewhat unsatisfactory. 2 Subsequent improvements have been reported using MeReO 3 and Rh±clay catalysts which produced aziridine carboxylates with high trans-selectivity. 3 In a related development, recently, it has been shown that reactions of a-diazoacetates and imines can also be catalyzed by Lewis acids (BF 3 . Et 2 O, Zn(OTf) 2 , lanthanide tri¯ates) to produce aziridine carboxylates, albeit in moderate yields. 4 Interestingly, a high degree of cis-selectivity has been observed in some of these Lewis acid catalyzed reactions. 4a,d Although in its infancy, this Lewis acid catalyzed aziridine synthesis, by virtue of its operational simplicity, mild reaction conditions and the prospect of asymmetric indiction 4c,f via the use of chirally modi®ed Lewis acids, holds more promise than the metal-catalyzed route described above and hence, if properly developed, can lead to broader synthetic rami®cations. 0040-4039/00/$ -see front matter # 2000 Elsevier Science Ltd. All rights reserved. P I I : S 0 0 4 0 -4 0 3 9 ( 0 0 ) 0 1 0 4 2 -X Tetrahedron Letters 41 (2000) 6245±6248 * Corresponding author. Fax: 91 33 4734266.
Synthesis of oxazolinyl aziridines
Tetrahedron Letters, 1999
Aziridinyllithiums 4a and 4b, which are stable at low temperature, can be generated by deprotonation of 3a and 3b. Oxazolinyl aziridines 5a-j and 6a-b have been prepared by the reaction of oxazolinyl aziridinyllithiums 4a and 4b with electrophiles. Aziridines 6c and 6d were, instead, synthesized by a Darzens-like reaction from 2-(1-chloroethyl)-2-oxazoline lb.