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The reaction of trimethyl(vinyl)silane 1 and dimethyl(divinyl)silane 2 with various sulfonamides in the oxidative system (tert -BuOCl + NaI) has been studied and shown to be an efficient approach for the synthesis of silylated N-heterocycles. Triflamide demonstrated the reactivity principally different from that of arenesulfonamides. With silane 1 , it afforded the products of iodochlorination and bis(triflamidation) (major), whereas arenesulfonamides gave N-arenesulfonylaziridines in up to 91% yield. Silane 2 with arenesulfonamides yielded the products of mono and bis(iodochlorination), mono and bis(aziridination), and 3,5-diiodo-4,4-dimethyl-1-(arylsulfonyl)-1,4-azasilinanes. By contrast, triflamide, apart from the products of halogenation and iodotriflamidation, unexpectedly gave 3-(trifluoromethylsulfonyl)-5-(triflamido)oxazolidine as the main product. The structure of most heterocyclic products is proved by X-ray analysis. The effect of the silyl group in the substrate and of the substituent in the reagent on the course of oxidative sulfamidation is discussed by comparing with all-carbon analogues. Image 1 • Vinyl silanes undergo via oxidative addition and heterocyclization when reacting with sulfonamides in oxidative conditions. • The reactivity of triflamide is principally different from that of arenesulfonamides. • Silylated mono- and diaziridines, N-sulfonyl-1,4-azasilinanes and 3-(triflyl)-5-(triflamido)oxazolidine are obtained. [ABSTRACT FROM AUTHOR]

In this account, we provide an overview of some recent advances in electrophilic amination methodologies that have been developed in the Kürti group over the last seven years. Our group's focus has been to develop novel amination methodologies that directly yield N -unprotected amine products. 1 Introduction 2 Amination of Boronic Acids 3 Aziridination of Unactivated Olefins 4 Rhodium-Catalyzed C–H Amination of Arenes 5 Synthesis of Carbazoles 6 Amination of Aryl- and Alkylmetals 7 Doubly Electrophilic N -Linchpin Reagents 8 Aza-Rubottom Oxidation of Silyl Enol Ethers 9 Summary [ABSTRACT FROM AUTHOR]

• Graphene oxide (GO)/GO-I 2 co-catalyzed green synthesis of tosylaziridine. • Strategy involves sequential oxidation of benzylic alcohol-nitrene insertion into MBH alkene. • Operational simplicity, use of water as solvent and ambient reaction conditions are utilized. • Excellent yield (88–96%), no by-product and recyclability of catalyst up to five times. Graphene oxide (GO)/GO-I 2 co-catalyzed green synthesis of tosylaziridine bearing keto and nitrile/ester functional groups is reported. The strategy involves sequential GO-catalyzed oxidation of benzylic alcohol and GO-I 2 catalyzed nitrene insertion into olefin of Morita-Baylis-Hillman adduct. Operational simplicity, use of water as solvent, ambient reaction conditions, excellent yield of products (88–96%) and recyclability of catalyst up to five times without any substantial change in morphology as well as catalytic efficiency are the salient features of the envisaged protocol. [ABSTRACT FROM AUTHOR]

Oxazolidinone synthesis through the coupling of carbon dioxide and aziridines was catalysed by an aluminium(salphen) complex at 50–100 °C and 1–10 bar pressure under solvent‐free conditions. The process was applicable to a variety of substituted aziridines, giving products with high regioselectivity. It involved the use of a sustainable and reusable aluminium‐based catalyst, used carbon dioxide as a C1 source and provided access to pharmaceutically important oxazolidinones as illustrated by a total synthesis of toloxatone. This protocol was scalable, and the catalyst could be recovered and reused. A catalytic cycle was proposed based on stereochemical, kinetic and Hammett studies. [ABSTRACT FROM AUTHOR]

Highlights from the article: To expand the scope of our asymmetric strategy to the synthesis of enantioenriched THIQ derivatives, we carried out reactions of I m-N,N i -dialkylaminophenyl methylidenemalonates B 6a-6c b with D-A aziridine B 2a b (Scheme). Pyrrolidinyl-substituted THIQ B 5k b and 4-morpholino-substituted THIQ B 5m b were obtained in moderate yields (58% and 64%) and enantioselectivities (79:21 er and 77:23 er) when the corresponding methylidenemalonates B 6a b and B 6c b were reacted with the D-A aziridine under the same reaction conditions. Inspired by these results, we further extended the scope of our asymmetric strategy to the synthesis of enantioenriched THIQ derivatives by employing I m-N,N i -dimethylaminophenyl , -unsaturated esters as the substrate (Scheme). Various D-A aziridines were tolerated under the reaction conditions, providing access to highly functionalized THIQ derivatives in good yields, with excellent diastereoselectivities (up to >30:1) and moderate enantioselectivities (up to 87:13 er).

The first enantioselective aza‐Darzens reaction of cyclic imines with α‐halogenated ketones was realized under mild reaction conditions by using amino‐acid‐derived bifunctional phosphonium salts as phase‐transfer promoters. A variety of structurally dense tri‐ and tetrasubstituted aziridine derivatives, containing benzofused heterocycles as well as spiro‐structures, were readily synthesized in high yields with excellent diastereo‐ and enantioselectivities (up to >20:1 d.r. and >99.9 % ee). The highly functionalized aziridine products could be easily transformed into different classes of biologically active compounds. [ABSTRACT FROM AUTHOR]

2H‐Azirines are useful precursors for the synthesis of a variety of chiral aziridine and amine derivatives with a range of biological activities. Owing to the ring strain and the presence of a C=N double bond, 2H‐azirines are more reactive than other types of ketimine, and undergo a range of enantioselective reactions, including reduction and Diels–Alder reactions, as well as nucleophilic addition to the C=N double bond. Therefore, the enantioselective reactions of 2H‐azirines has become a hot topic, in particular within the last few years. In this Minireview, we focus on the enantioselective reactions of 2H‐azirines by using catalytic or stoichiometric amounts of chiral additives, the reaction mechanisms, and the applications of these reactions of 2H‐azirines and related compounds in organic synthesis. [ABSTRACT FROM AUTHOR]

Metal-free ring opening reactions of activated and unactivated aziridines with different silyl chalcogenides are described. Judicious tuning of the reaction conditions enables the synthesis of chiral enantioenriched N-Ts and N-Boc 1,2-mercaptoamines in good yields from the corresponding aziridines and bis(trimethylsilyl)sulfide. N-Protected and N-H unactivated aziridines are efficiently converted into the corresponding β-arylchalcogeno amines upon treatment with suitable arylchalcogenosilanes. The silicon-mediated ring opening reactions proceed with excellent regioselectivity and stereospecificity, allowing to access a wide array of synthetically and biologically valuable enantioenriched chalcogenoamines. [ABSTRACT FROM AUTHOR]

An efficient method for the direct synthesis of aziridine‐containing chiral tridentate ligands was developed from enantiopure aziridines and salicylaldehydes. The method achieved the regiospecific cleavage of more substituted C−N bonds of aziridines through an iminium‐mediated self‐ring opening reaction of aziridines with up to 95% yield and complete inversion of configuration. The (S)‐2‐alkylaziridine‐derived tridentate ligands displayed excellent activity and stereoselectivity in the zinc trifluoromethanesulfonate‐catalyzed asymmetric aldol reactions of acetone and aromatic aldehydes. [ABSTRACT FROM AUTHOR]

Acylimidodicarbonates obtained from aziridine-2-carboxamides through Davidsen bis-Boc activation react with amine nucleophiles under mild conditions to form tertiary aziridine-2-carboxylic acid amides. NH aziridine-2-carboxylic acid amides were obtained by hydrogenolythic deprotection of N-Cbz derivatives. [ABSTRACT FROM AUTHOR]

Abstract Rhodium(I)-catalyzed intermolecular cycloadditions of alkynes with vinyl aziridines bearing a conjugated carbonyl group in the olefin moiety followed by the double migration resulted in the formation of pyrrole derivatives in a one pot fashion. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

A new metal–organic framework (MOF) with the formula [Eu 2 Cu 2 I 2 (IN) 6 (DMF) 4 ]·4DMF (1) (HIN = isonicotinic acid, DMF = N,N-dimethylformamide) based on lanthanide ions and copper iodide clusters (Cu 2 I 2) have been successfully constructed and characterized. Structural analysis indicates that the [Cu 2 I 2 ] cluster-based lanthanide MOF 1 displays a two-dimensional plane with sql topology. Catalytic study indicates that MOF 1 can efficiently catalyze the propargylic alcohols or aziridines with CO 2 under mild conditions. What's more, 1 as a heterogeneous catalyst can be recycled at least five times without obvious loss of catalytic performance. To our best knowledge, it is a rare example of a [Cu 2 I 2 ] cluster-based lanthanide MOF catalyst that can catalyze both aziridines and propargylic amines with CO 2 simultaneously under mild conditions. [Display omitted] • A novel MOF 1 has been constructed and characterized. • MOF 1 can catalyze aziridines/propargylic amines with CO 2 under mild conditions. • MOF 1 can be recycled at least five times without obvious loss of catalytic performance. [ABSTRACT FROM AUTHOR]

The class I major histocompatibility complex (MHC) glycoprotein HLA-B27 binds short peptides containing arginine at peptide position 2 (P2). The HLA-B27/peptide complex is recognized by T cells both as part of the development of the repertoire of T cells in the cellular immune system and during activation of cytotoxic T cells. Based on the three-dimensional structure of HLA-B27, we have synthesized a ligand with an aziridine-containing side chain designed to mimic arginine and to bind covalently in the arginine-specific P2 pocket of HLA-B27. Using tryptic digestion followed by mass spectrometry and amino acid sequencing, the aziridine-containing ligand is shown to alkylate specifically cysteine 67 of HLA-B27. Neither free cysteine in solution nor an exposed cysteine on a class II MHC molecule can be alkylated, showing that specific recognition between the anchor side-chain pocket of an MHC class I protein and the designed ligand (propinquity) is necessary to induce the selective covalent reaction with the MHC class I molecule.

A sequential three-component process is described, starting from 3-arylmethylene-2,5-piperazinediones and involving a one-pot sequence of reactions achieving regioselective opening of the 2,5-diketopiperazine ring and diastereoselective generation of an aziridine ring. This method allows the preparation of N-unprotected, trisubstituted aziridines bearing a peptide side chain under mild conditions. Their transformation into β-trifluoroacetamido-α-ketoamide and α,β-diketoamide frameworks was also achieved in a single step.

This work reports a straightforward regioselective synthetic methodology to prepare α-aminophosphine oxides and phosphonates through the addition of oxygen and sulfur nucleophiles to the C–N double bond of 2H-azirine derivatives. Determined by the nature of the nucleophile, different α-aminophosphorus compounds may be obtained. For instance, aliphatic alcohols such as methanol or ethanol afford α-aminophosphine oxide and phosphonate acetals after N–C3 ring opening of the intermediate aziridine. However, addition of 2,2,2-trifluoroethanol, phenols, substituted benzenthiols or ethanethiol to 2H-azirine phosphine oxides or phosphonates yields allylic α-aminophosphine oxides and phosphonates in good to high general yields. In some cases, the intermediate aziridine attained by the nucleophilic addition of O- or S-nucleophiles to the starting 2H-azirine may be isolated and characterized before ring opening. Additionally, the cytotoxic effect on cell lines derived from human lung adenocarcinoma (A549) and non-malignant cells (MCR-5) was also screened. Some α-aminophosphorus derivatives exhibited very good activity against the A549 cell line in vitro. Furthermore, selectivity towards cancer cell (A549) over non-malignant cells (MCR-5) has been detected in almost all compounds tested.

Commercially available poly(lactic acid) exhibits poor hydrolytic stability, which makes it impossible for use in durable applications. Therefore, a novel hydrolysis inhibitor based on an aziridine derivative as well as a novel stabilizer composition, containing an aziridine derivative and an acid scavenger, were investigated to improve the hydrolytic stability. To evaluate the stabilizing effect, the melt volume rate (MVR) and molecular weight were monitored during an accelerated hydrolytic aging in water at elevated temperatures. Temperatures were selected according to the glass transition temperature (~60 °C) of PLA. It was shown that the novel hydrolysis inhibitor as well as the novel stabilizer composition exhibited excellent performance during hydrolytic aging, exceeding commercially available alternatives, e.g., polymeric carbodiimides. A molecular weight analysis resulted in a molecular weight decrease of only 10% during approximately 850 h and up to 20% after 1200 h of hydrolytic aging, whereas poly(lactic acid) stabilized with a commercial polycarbodiimide revealed comparable molecular weight reductions after only 300 h. Furthermore, the stabilization mechanism of the aziridine derivative alone, as well as in the synergistic combination with the acid scavenger (calcium hydrotalcite), was investigated using nuclear magnetic resonance (NMR) spectroscopy. In addition to an improved hydrolytic stability, the thermal properties were also enhanced compared to polymeric carbodiimides.

l-Isovaline biosynthesis by TqaLFM- ti from Tolypocladium inflatum was demonstrated in vitro . The biochemical analysis of the α-ketoglutarate-dependent oxygenase TqaL- ti revealed that it produces (2 S ,3 S )-3-ethyl-3-methylaziridine-2-carboxylic acid from l-isoleucine, thus exhibiting a stereoselectivity different from those of the reported homologues. Remarkably, a single mutation on I295 in TqaL- ti completely exchanged its stereoselectivity to produce the C-3 stereoisomer. TqaFM- ti generates d-isovaline from (2 S ,3 R )-aziridine-2-carboxylic acid, suggesting that the stereochemistry of the TqaL product defines that of isovaline.

N-Trifluoromethylated organics may be applied in drug design, agrochemical synthesis, and materials science, among other areas. Yet, despite recent advances in the synthesis of aliphatic, cyclic and heterocyclic N-trifluoromethyl compounds, no strategy based on trifluoromethyl nitrene has hitherto been explored. Here we describe the formation of triplet trifluoromethyl nitrene from azidotrifluoromethane, a stable and safe-to-use precursor, by visible light photocatalysis. The addition of CF 3 N to alkenes via biradical intermediates afforded previously unknown aziridines substituted with trifluoromethyl group on the nitrogen atom. The obtained aziridines were converted into either N-trifluoromethylimidazolines, via formal [3+2] cycloaddition with nitriles, mediated by a Lewis acid, or into N-trifluoromethylaldimines, via ring opening and aryl group migration mediated by a strong Brønsted acid. Our findings open new opportunities for the development of novel classes of N-CF 3 compounds with possible applications in the life sciences., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Epoxides, aziridines, and cyclopropanes are found in various medicinal natural products, including polyketides, terpenes, peptides, and alkaloids. Many classes of biosynthetic enzymes are involved in constructing these ring structures during their biosynthesis. This review summarizes our current knowledge regarding how α-ketoglutarate-dependent nonheme iron enzymes catalyze the formation of epoxides, aziridines, and cyclopropanes in nature, with a focus on enzyme mechanisms., (© 2023. The Author(s).)

A conceptually novel, high‐yielding, mono‐ or bis‐homologation was realized with lithium halocarbenoids and enables the one‐step, fully chemocontrolled assembly of a new class of quaternary trifluoromethyl aziridines. Trifluoroacetimidoyl chlorides (TFAICs) act as convenient electrophilic platforms, enabling the addition of either one or two homologating elements by simply controlling the stoichiometry of the process. Mechanistic studies highlighted that the homologation event, carried out with two different carbenoids (LiCH2Cl and LiCH2F), leads to fluoromethyl analogues in which the first nucleophile is employed for constructing the cycle and the second for decorating the resulting molecular architecture. Mono‐ or bis‐homologation was realized with lithium halocarbenoids for the assembly of trifluoromethyl aziridines. Trifluoroacetimidoyl chlorides act as electrophilic platforms, enabling the addition of either one or two homologating elements. Use of two different carbenoids leads to fluoromethyl analogues in which the first nucleophile is employed for constructing the cycle and the second one for decorating the resulting molecular architecture. [ABSTRACT FROM AUTHOR]

The asymmetric synthesis of (3R,5S)-5-(aminomethyl)-3-(4- methoxyphenyl)dihydrofuran-2(3H)-one, as the most potent selective inactivator of monoamine B, was successfully achieved by applying a newly developed synthetic method toward the key γ-aminomethyl-γ- lactone via intramolecular aziridine ring opening in 63% overall yield from a commercial starting material. [ABSTRACT FROM AUTHOR]

The c-phosphanylimine L1 was employed for the synthesis of the novel titanaaziridine 1 with an intramolecular phosphine donor side following a reductive complexation route. This coordination mode is new for c-phosphanylimines and compound 1 is the first group 4 complex featuring a c-phosphanylimine ligand. [ABSTRACT FROM AUTHOR]

Cyclophellitol aziridine and its configurational and functional isomers are powerful covalent inhibitors of retaining glycosidases, and find application in fundamental studies on glycosidases, amongst others in relation to inherited lysosomal storage disorders caused by glycosidase malfunctioning. Few direct and stereoselective aziridination methodologies are known for the synthesis of cyclophellitol aziridines. Herein, we present our studies on the scope of direct 3‐amino‐2‐(trifluoromethyl)quinazolin‐4(3H)‐one‐mediated aziridination on a variety of configurational and functional cyclohexenol isosters. We demonstrate that the aziridination can be directed by an allylic or homoallylic hydroxyl through H‐bonding and that steric hindrance plays a key role in the diastereoselectivity of the reaction. This work describes direct aziridination reactions on differently substituted glycoside configured cyclohexenes with 3‐amino‐2‐(trifluoromethyl)quinazolin‐4(3H)‐one as nitrogen donor. It is shown that aziridination can be directed by allylic or homoallylic hydroxyls through H‐bonding, and that steric hindrance plays an essential role in the diastereoselective outcome of the final cyclitols aziridines. [ABSTRACT FROM AUTHOR]

Copper acetylide was reacted with isothiocyanate and aziridines to form 1,4‐thiomorpholine derivatives. Reaction outcome depends highly on the reaction conditions and the particular solvent employed. Optimum conditions are developed using copper iodide in hexafluoro‐2‐isopropanol at 60°C. Both the alkyl‐substituted and aryl‐substituted aziridines and terminal alkynes were studied. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Enantiopure aminocyclooctene carbonitriles were accessed in g quantity. • New unsaturated β-lactams were achieved. • Hydroxyaminocyclooctene carbonitriles were obtained via aziridine ring opening. • The absolute stereochemistry of the synthesized compounds was determined by X-ray. Abstract Enantiopure β-aminocyclooctenenitriles, as precursors of β-amino acids and β-lactams, were synthesized from a readily available chloroalkene nitrile and (S)-methylbenzylamine via a straightforward substitution reaction and purified by crystallization. Acidic hydrolysis of the nitrile groups to their corresponding amides followed by DCC assisted carbonyl group activation gave novel α,β-unsaturated lactams. The treatment of 3-bromo-8-chlorocyclooctenecarbonitrile with (S)-methylbenzylamine furnished a diastereomeric mixture of bromoaminocyclooctenecarbonitriles via an S N 2′ pathway rather than bromide substitution via an S N 2 pathway. The diastereomeric mixture of bromoaminocyclooctanecarbonitriles provided two novel aziridines upon heating. TFA catalyzed aziridine ring opening gave γ-hydroxyl-β-aminocyclooctenecarbonitriles and γ-amino-β-hydroxycyclooctenecarbonitriles. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The allylic zinc halide acts in different modes for different electrophiles. • Zinc alyllic halide is the source of halide in aziriding ring-opening. • A probable reaction mechanism was proposed. • This approach bears broad substrate scopes for aziridines and carbonyls. Abstract We have observed that the allylic zinc halide under identical reaction conditions acts in different modes for different electrophiles. For Ts-aziridines the halide part of the allylic halide has been introduced as a nucleophile and for the carbonyl compounds the simple allylation reaction occurs. To the best of our knowledge this is the first report where the allylic zinc halide is the source of halide acting as nucleophile. The main advantages of the present procedure are easy to handle, no need of inert atmosphere, mild reaction conditions, and applicability to a wide variety of substrates for aziridines and carbonyl compounds. [ABSTRACT FROM AUTHOR]

Al‐catalyzed stereospecific tandem C−N/C−Se bond formation of chiral aziridines with isoselenocyanates is described with 90–99% ee and 77–91% yields. The mechanistic investigation using the computational study suggests that the reaction involves a concerted pathway (SN2). The selectivity and substrate scope are the important practical features. [ABSTRACT FROM AUTHOR]

Abstract A series of new optically pure phosphine oxides containing chiral aziridine subunit were synthesized in good yields and applied as organocatalysts in asymmetric Michael reaction of various aliphatic aldehydes with β-nitrostyrene. The corresponding organocatalysts were synthesized starting from optically pure aziridines in a few simple efficient steps. The appropriate Michael adducts were obtained in most cases in very high chemical yield (up to 97%), excellent enantioselectivity (up to 98% of ee) and diastereoselectivity (up to 95:5 of dr). Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

The reaction between N‐substituted‐2‐arylaziridines and CO2 is efficiently promoted by ruthenium(VI) imidoporphyrin complexes and yields a mixture of 5‐aryl (A) and 4‐aryl (B) substituted oxazolidin‐2‐ones with a regioisomeric A/B ratio up to 99:1. Several oxazolidin‐2‐one molecules were synthesized at 100 °C and 0.6 MPa of carbon dioxide by using the low catalytic loading of 1 mol‐%. The formation of a deactivated compound, deriving from the ruthenium catalyst, suggested a possible catalytic role of imido nitrogen atoms. The catalytic activity of ruthenium(IV) bis‐imidoporphyrins in promoting the insertion of CO2 into aziridines, forming oxazolidin‐2‐ones, is reported. [ABSTRACT FROM AUTHOR]

Here, we present a catalytic asymmetric and site‐selective reaction of naphthols, realizing diversiform reactions in asymmetric dearomatization or O‐alkylation with aziridines, and the reason for the switchable reactivity is formally analyzed with different type of substrates under different conditions. [ABSTRACT FROM AUTHOR]

In this study, we report the synthesis, characterization and utilization of 99mTc-labelled polyethylenimine-entrapped gold nanoparticles (99mTc-Au-PENPs) for dual mode single-photon emission computed tomography/computed tomography (SPECT/CT) imaging applications. Polyethylenimine (PEI) was selected as a platform to conjugate with diethylene triamine pentacetate acid (DTPA) and polyethylene glycol monomethyl ether to synthesize Au PENPs, followed by acetylation or hydroxylation modification of the remaining PEI surface amine groups and radiolabelling of 99mTc. The generated multifunctional 99mTc-Au-PENPs with different surface groups (acetyl or hydroxyl) were characterized via different methods. The Au PENPs before 99mTc labelling are colloidally stable, haemocompatibility and noncytotoxic at an Au concentration up to 100 μM. The 99mTc-labelled Au PENPs exhibit high radiochemical purity, good stability and SPECT/CT imaging performance of different organs and lymph node. The designed strategy to use the radionuclide labelling technique and PEI-facilitated versatile nanoplatform may be extended to develop various novel nanoprobes for precision imaging applications. [ABSTRACT FROM AUTHOR]

Aziridines, the nitrogen counterparts of epoxides, are among the most challenging and intriguing heterocycles in organic chemistry, since they not only represent the endpoints of several total syntheses as common scaffolds in natural products, but also act as crucial precursors of complex molecules. The present review provides a brief overview of aziridine derivatives as well as the authors' choice of published papers that highlight recent enhancements concerning asymmetric organocatalytic strategies involved in aziridination reactions. Covalent or not? The present review provides a concise overview of current employments of asymmetric organocatalysis toward the enantioselective synthesis of aziridine derivatives. Specifically, after briefly introducing peculiar properties of aziridines, outstanding examples of covalent and non‐covalent activation methods are reported. [ABSTRACT FROM AUTHOR]

This review presents an overview on the recent advances in the catalytic enantioselective Darzens and aza‐Darzens reactions for the synthesis of enantiopure three‐membered oxygen and nitrogen containing heterocycles. Since the synthesis of epoxides is the most widely explored, compared to their nitrogen counterparts, particularly true when asymmetric synthesis are considered, in the last decades several methodologies have appeared or improved and are now available for the preparation of aziridines in a highly stereo‐ and enantioselective manner. Catalytic asymmetric Darzens and aza‐Darzens reaction constitute an important tool in modern organic chemistry, as there is an increased interest in bioactive natural products and pharmaceutical agents that contain these skeletons. Chiral epoxides and aziridines: In the last decades several methodologies have appeared or improved and are now available for the preparation of epoxides and aziridines in a highly stereo‐ and enantioselective manner. This review covers the most recent advances related to the catalytic enantioselective Darzens and aza‐Darzens reactions for the synthesis of chiral epoxides and aziridines. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Electrocyclic ring opening of the parent aziridines has high barrier. • Substituents lower barriers of ring opening of aziridines. • In the reaction of azomethine ylide with acealdehyde, formation of 4-methyl isomer is favoured over 3-isomer. • Exo isomer is favoured over endo isomer. • Ring-opening is rate-determining step. Abstract This work investigated computationally with density functional theory calculations at the M06/6-311G∗ level, the ring opening reaction of various methyl-, phenyl- and carbonyl- substituted aziridines to obtain azomethine ylides and the subsequent 1,3-dipolar cycloaddition reaction with acetaldehyde leading to 3-methyl and 4-methyl regioisomers and endo - and exo - stereoisomers. The activation barrier for the electrocyclic ring opening of the parent aziridine is very high (51.3 kcal/mol) but is lowered by at least 15.5 kcal/mol upon methyl and ester group substitutions. In the reaction of 1,3-diphenyl-2,2-methoxycarbonylaziridine A2 with acetaldehyde, the ring opening step is rate-determining with an activation barrier of 28.9 kcal/mol. The activation barrier for the formation of the 4-methyl isomer from this reaction is at least 7.4 kcal/mol lower than that for the formation of the 3-methyl isomer, which is in accord with the experimentally-observed regioselectivity. Also, the formation of the exo isomer is more favoured than the endo isomer as the barrier of the former is 2.7 kcal/mol compared to 6.1 kcal/mol for the latter. There is an inverse correlation between the activation barriers for the electrocyclic cleavage of the aziridines and the electrophilicities of the resulting azomethine ylides. The results are rationalized in terms of perturbation molecular orbital theory. [ABSTRACT FROM AUTHOR]

Chiral aziridine-epoxyaldehydes (d.r. up to 99:1) have been obtained from stereoselective epoxidation of aziridin-2-acrylaldehyde in the presence of proline-derivatived catalyst. The desired aziridine-epoxyaldehydes can give valuable azirinols via ring opening reaction catalyzed by NHC catalyst. These azirinol derivatives are good candidates for the synthesis of more functionalized structures. [ABSTRACT FROM AUTHOR]

Mono- and disubstituted aziridines derived from sterically hindered olefins of the adamantane series are synthesized. The opening of the aziridine ring under the action of acids is quite a regio- and stereoselective process. Depending on the nature of the nucleophilic agent, the opening of the 2,2-disubstituted aziridine ring can occur by the SN1 or SN2 mechanism. [ABSTRACT FROM AUTHOR]

A ß-monofluoromethylated vinyl sulfonium salt, prepared in situ from a precursor γ-fluoro ß-acetoxypropyl sulfonium salt under mild basic conditions, reacted with a lvariety of active methylene compounds or a primary sulfone amide under basic conditions to provide the corresponding monofluoromethylated three-membered rings in good-to-excellent yields. This new sulfonium reagent should permit easy access to a variety of important monofluoromethylated organic compounds. [ABSTRACT FROM AUTHOR]

Synthesis of oxazolidines has been reported from aziridines by the reaction with formic acid and formaldehyde in neat conditions. We have also observed a regio‐selective nucleophilic ring opening of aziridines by HCOOH under same conditions in absence of formaldehyde where the HCOO− ion acts as a nucleophile. In this present method formic acid is not acting as reducing agent as classical organic reactions. The formic acid initially activates the aziridines whereas the formate group generated from formic acid acts as a nucleophile itself instead of the source of hydride ion affording the nucleophilic ring opening products. The synthesized formate ester was successfully hydrolyzed to the corresponding hydroxyl compound which is the key building block for the synthesis of heterocycles. Operational simplicity, mild and neat reaction conditions, broad substrates scope, good yields and uses of less expensive reagents are the notable advantages of the present procedures. A convenient method was developed for the synthesis of oxazolidines from aziridines by the reaction with formic acid and formaldehyde. In the course of the study we have observed a clear nucleophilic ring opening of aziridines under neat conditions in presence of only formic acid and aziridine, where the HCOO− ion acts as a nucleophile. [ABSTRACT FROM AUTHOR]