Hypervalent iodine-mediated intramolecular alkene halocyclisation

• Charu Bansal,
• Oliver Ruggles,
• Albert C. Rowett and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 3113–3133, doi:10.3762/bjoc.20.258

• from interaction with the HVI, that is then attacked by the alkene. While the fluoroamination of alkenes to form 4-membered azetidines has not been reported, an exo fluorocyclisation to form 3-membered aziridines with an adjacent fluorine was reported by Jacobsen in 2018 (Scheme 9) [34]. The synthesis

• -fluorinated tosylated aziridines 15 with good tolerance to styrenyl arenes with electron-withdrawing groups on them. The yields of product dropped off significantly when the ring did not contain an electron-withdrawing group on it. In 2023, Šmit and co-workers conducted an in-depth mechanistic study on the

Advances in the use of metal-free tetrapyrrolic macrocycles as catalysts

• Mandeep K. Chahal

Beilstein J. Org. Chem. 2024, 20, 3085–3112, doi:10.3762/bjoc.20.257

• DFT studies to elucidate the mechanism of CO2 cycloaddition to aziridines using a metal-free protonated porphyrin macrocycle and found that the catalytic cycle started with simultaneous activation of both CO2 and N-butyl-2-phenylaziridine (69b). The main strategies used in metal-free porphyrin

A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis

• Nian Li,
• Ruzal Sitdikov,
• Ajit Prabhakar Kale,
• Joost Steverlynck,
• Bo Li and
• Magnus Rueping

Beilstein J. Org. Chem. 2024, 20, 2500–2566, doi:10.3762/bjoc.20.214

• product (Scheme 15). The synthesis of aziridines can be achieved via the formation of nitrenes in either a metal-catalyzed or metal-free fashion. In this context, Wickens and colleagues presented a remarkable dication pool strategy for accessing N-alkylaziridines via metastable dicationic intermediates

Hydrogen-bond activation enables aziridination of unactivated olefins with simple iminoiodinanes

• Phong Thai,
• Lauv Patel,
• Diyasha Manna and
• David C. Powers

Beilstein J. Org. Chem. 2024, 20, 2305–2312, doi:10.3762/bjoc.20.197

• ]. Iminoiodinanes (ArI=NR) are a subclass of hypervalent iodine reagents that function as nitrene equivalents in synthesis [5][6]. The direct reaction of iminoiodinanes with olefins, which could be envisioned to give rise to aziridines directly, is typically not observed and thus families of transition metal

• corresponding aziridines in modest to high isolated yields: 3b (80%), 3a (46%), and 3c (36%), respectively. Acyclic olefin 1-hexene underwent aziridination to 3d in 79% yield (reaction performed at 50 °C); aziridination of vinylcyclohexane proceeded in 67% yield of 3e. Allylbenzene engaged in aziridination to

• ) and N-p-methoxysulfonyl (6h) aziridines obtained each in 22% yield; the drug topiramate could also be transferred to furnish aziridine 6j in 11% yield). We carried out a series of experiments to clarify the origin of the observed reactivity enhancement of N-arylsulfonyliminoiodinanes in the presence

Efficient synthesis of aziridinecyclooctanediol and 3-aminocyclooctanetriol

• Emine Salamci and
• Ayse Kilic Lafzi

Beilstein J. Org. Chem. 2022, 18, 1539–1543, doi:10.3762/bjoc.18.163

• -azido-3,8-bis(benzyloxy)cyclooctyl methanesulfonate with Zn/NH4Cl and debenzylation resulted in the target aziridinecyclooctanediol. Keywords: aminocyclitols; aminocyclooctanetriol; azides; aziridines; aziridinecyclooctanediol; Introduction Aziridines are the smallest nitrogen-containing heterocycles

• and they are important building blocks in the synthesis as well as substructures of a number of biologically active natural and unnatural products [1][2][3][4][5][6][7][8]. Aziridines are valuable synthetic intermediates for the preparation of structurally complex molecules because of their

Dienophilic reactivity of 2-phosphaindolizines: a conceptual DFT investigation

• Nosheen Beig,
• Aarti Peswani and
• Raj Kumar Bansal

Beilstein J. Org. Chem. 2022, 18, 1217–1224, doi:10.3762/bjoc.18.127

• independent of the basis sets [33]. In view of this, we carried out all calculations at the B3LYP/6-31+G (d) level of theory. Furthermore, Phukan et al. [32] calculated electrophilicity indices of a number of aziridines in the gas and solvent phases and observed that in both cases, a similar pattern of

Efficient synthesis of ethyl 2-(oxazolin-2-yl)alkanoates via ethoxycarbonylketene-induced electrophilic ring expansion of aziridines

• Yelong Lei and
• Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 70–76, doi:10.3762/bjoc.18.6

• alkoxycarbonylketenes, which undergo an electrophilic ring expansion with aziridines to afford alkyl 2-(oxazolin-2-yl)alkanoates in good to excellent yields under microwave heating. The method is a convenient and clean reaction without any activators and catalysts and can be also applied in the synthesis of 2-(oxazolin

• in the presence of electrophilic reagents [18][19] (Scheme 1d). Aziridines can be considered as the NCC structural fragment after ring-opening and have been applied in the synthesis of aziridine-imine-containing chiral tridentate ligands [20], 2-alkylideneoxazolidines [21], and N-vinylamides [22]. We

• envisioned that the reaction of ethoxycarbonylketenes and aziridines can be applied for the synthesis of ethyl 2-(oxazolin-2-yl)alkanoates. Herein, we present our convenient and clean synthesis of ethyl 2-(oxazolin-2-yl)alkanoates from 2-diazo-3-oxoalkanoates and 2-arylaziridines (Scheme 1e). Results and

Allylic alcohols and amines by carbenoid eliminative cross-coupling using epoxides or aziridines

• Matthew J. Fleming and
• David M. Hodgson

Beilstein J. Org. Chem. 2021, 17, 2385–2389, doi:10.3762/bjoc.17.155

• Matthew J. Fleming David M. Hodgson Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, United Kingdom 10.3762/bjoc.17.155 Abstract α-Lithiated terminal epoxides and N-(tert-butylsulfonyl)aziridines undergo eliminative cross-coupling with

• alkoxide. Keywords: alkenes; aziridines; epoxides; lithiation; synthetic methods; Introduction Methods for the convergent generation of alkenes can be of significant utility in organic synthesis [1]. A relatively under-examined approach is through the interaction of two carbenoids [2]. Dimerisation of

• carbenoids may compete with a desired carbenoid transformation although its value has been demonstrated in, for example, our studies on lithium 2,2,6,6-tetramethylpiperidide (1, LTMP)-induced syntheses of 2-ene-1,4-diols and 2-ene-1,4-diamines from terminal epoxides [3] and aziridines [4][5], respectively

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• example utilizing this strategy was provided by Jacobsen and co-workers for the desymmetrization of meso-aziridines 29. In their work, the bifunctional phosphinothiourea catalyst 31 promoted the C–N bond cleavage by hydrochloric acid upon initial protonation (Scheme 7) [55]. Subsequently, the catalyst

• -bound chloride anion performs a SN2-type attack on the coordinated benzoyl-protected aziridine, which leads to a formal addition of HCl. This concept was further developed and successfully employed by Ooi in the desymmetrization of meso-aziridines 32 with TMSX as chloride and bromide with similar

• ) vinylboronic acids. Enantioselective selenocyclization catalyzed by squaramide 28. Desymmetrization of meso-aziridines catalyzed by bifunctional thiourea catalyst 31. Anion-binding-catalyzed desymmetrization of a) meso-aziridines catalyzed by chiral triazolium catalyst 34 by Ooi et al., and b) oxetans

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• important tool in the asymmetric synthesis of aziridines [25][26], α-amino acids [27][28], β-amino acids [23][29] and branched α-amines [30][31]. The Darzens-type asymmetric synthesis of N-(p-toluenesulfinyl)aziridine 2-carboxylate esters (7 and 8) was described through the addition of lithium α

• -butanesulfonamide and applications in some nucleophilic additions, the next sections will describe the synthesis of several alkaloids according to the size of the heterocycles. We regret in advance that some contributions are excluded in order to maintain a concise format. Review Asymmetric synthesis of aziridines

• Saturated nitrogen-containing three-membered heterocycles have attracted increasing interest in recent years because compounds with this structural motif display quite diverse pharmacological activities. Chiral aziridines [51] also play an important role in asymmetric synthesis because they can act both as

A sustainable strategy for the straightforward preparation of 2H-azirines and highly functionalized NH-aziridines from vinyl azides using a single solvent flow-batch approach

• Michael Andresini,
• Leonardo Degannaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2021, 17, 203–209, doi:10.3762/bjoc.17.20

• preparation of 2H-azirines and their stereoselective transformation into highly functionalized NH-aziridines, starting from vinyl azides and organolithium compounds. The protocol has been developed using cyclopentyl methyl ether (CPME) as an environmentally benign solvent, resulting into a sustainable, safe

• and potentially automatable method for the synthesis of interesting strained compounds. Keywords: aziridines; 2H-azirines; flow chemistry; green chemistry; organolithium compounds; Introduction Since their conception in the early 1990s, Green Chemistry Principles (GCP) have been applied with

• ]. Within the synthetic chemistry context, the preparation of aziridines still generates interest, mostly because of their importance as source for drug prototypes and drug discovery leads [12]. Interestingly, important advances have been recently addressed in the synthesis of NH-aziridines directly from

Selective and reversible 1,3-dipolar cycloaddition of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes with 1,3-diphenylprop-2-en-1-ones under microwave irradiation

• Alexander P. Molchanov,
• Mariia M. Efremova,
• Mariya A. Kryukova and
• Mikhail A. Kuznetsov

Beilstein J. Org. Chem. 2020, 16, 2679–2686, doi:10.3762/bjoc.16.218

• that the Lewis acid-catalyzed reaction of diaziridines with donor–acceptor cyclopropanes and aziridines affords the perhydropyridazine or triazine derivatives, respectively, in good yields [31][32][33]. The use of microwave irradiation in organic synthesis complies with the principles of green

One-pot synthesis of oxazolidinones and five-membered cyclic carbonates from epoxides and chlorosulfonyl isocyanate: theoretical evidence for an asynchronous concerted pathway

• Esra Demir,
• Ozlem Sari,
• Yasin Çetinkaya,
• Ufuk Atmaca,
• Safiye Sağ Erdem and
• Murat Çelik

Beilstein J. Org. Chem. 2020, 16, 1805–1819, doi:10.3762/bjoc.16.148

• multicomponent reaction of rare-earth metal amides [28], the reaction of CO2 with propargylamines or aziridines [29][30] and the cycloaddition reaction of epoxides with isocyanates [31][32]. On the other hand, for the synthesis of five-membered cyclic carbonates, the cycloaddition of CO2 to epoxides, the

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• reagent for the nucleophilic ring expansion of three-membered heterocycles. It was successfully applied in the preparation of oxetanes and azetidines via the ring expansions of oxiranes [116][117][118] and aziridines [119][120]. However, both thiiranes and thietanes were less stable than the corresponding

Fluorinated phenylalanines: synthesis and pharmaceutical applications

• Laila F. Awad and
• Mohammed Salah Ayoup

Beilstein J. Org. Chem. 2020, 16, 1022–1050, doi:10.3762/bjoc.16.91

• derivatives by HF/Py The ring opening reaction of aziridines 138a,b by treatment with hydrogen fluoride in pyridine afforded 3-fluorophenylalanine esters 139a,b. The subsequent enzymatic hydrolysis of esters 139a,b gave the threo-isomer 136 in an enantiomerically pure form [68][69] (Scheme 31). On the other

Copper catalysis with redox-active ligands

• Agnideep Das,
• Yufeng Ren,
• Cheriehan Hessin and
• Marine Desage-El Murr

Beilstein J. Org. Chem. 2020, 16, 858–870, doi:10.3762/bjoc.16.77

• molecular spin catalysis is reminiscent of the multistate reactivity observed at the metal center, for example in heme enzymes [38][39]. A wide range of substrates could be converted including mono-substituted aziridines (21a, 21b and 21j), disubstituted aziridines (21c–h and 21l,m), and more challenging

• scaffolds such as gem-disubstituted (21k) and trisubstituted (21i and 21n,o) aziridines (Scheme 11). Furthermore, the reaction conditions are compatible with aldehyde, ester or ketone functions. Metalloenzymes routinely rely on 3d metals and amino acid-derived coordination spheres to perform complex (multi

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• . This same research group recently reported on the addition of silyl Grignard reagents to aziridines under copper catalysis [83]. While the use of RMgX led to high chemical yields of the desired products, the corresponding catalytic Cu/zinc reagents gave poor yields (ca. 20%; Scheme 45). A library of

• aminosilane derivatives was prepared using this strategy to result in branched silyl compounds 272–276. The addition of Grignard-derived copper reagents was stereospecific, where cis-aziridines gave trans products (e.g., 274), and vice versa (e.g., 275). The important aspect shown here is the utility of

• PhMe2Si group could also be prepared in moderate yield (276). The regiocontrolled ring opening reactions of the same aryl-substituted aziridines 277 have also been shown by Minakata and Takeda et al. to be susceptible to dual Pd/Cu catalysis. Depending upon the ligand on each metal, either the 2 or 3

Asymmetric synthesis of CF₂-functionalized aziridines by combined strong Brønsted acid catalysis

• Xing-Fa Tan,
• Fa-Guang Zhang and
• Jun-An Ma

Beilstein J. Org. Chem. 2020, 16, 638–644, doi:10.3762/bjoc.16.60

• Tianjin University, Fuzhou 350207, China 10.3762/bjoc.16.60 Abstract A diastereo- and enantioselective approach to access chiral CF2-functionalized aziridines from difluorodiazoethyl phenyl sulfone (PhSO2CF2CHN2) and in situ-formed aldimines is described. This multicomponent reaction is enabled by a

• combined strong Brønsted acid catalytic platform consisting of a chiral disulfonimide and 2-carboxyphenylboronic acid. The optical purity of the obtained CF2-substituted aziridines could be further improved by a practical dissolution–filtration procedure. Keywords: aziridines; chiral disulfonimides

• ; difluoromethyl compounds; fluorinated diazo reagents; strong Brønsted acids; Introduction Chiral aziridines are prevalently found in natural products and artificially made bioactive molecules, thus receiving significant attention in the past decades [1][2][3][4][5][6]. Among them, the introduction of fluorine

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• in lower molecular weight products caused by cleavage of the methine chain and conjugate acid, see Equation 7 [5][63]. The latter can initiate ring opening polymerization of aziridines [5] and oxiranes [63]. We also prefer to use the term conjugate acid instead of proton. The use of the latter widely

• that inhibits cationic polymerization of epoxides [5]. Though conjugate acids are formed according to the routes shown in Scheme 6, cationic photopolymerization only succeeded with aziridines [5]. The different reaction mechanism occurring with such monomers explains these different observations [92

• ]. Aziridines tolerate nucleophiles because chain growth requests the ammonium ion [93][94][95][96]. On the other hand, chain propagation includes the carbocation in the case of oxiranes and oxetanes [92]. More of interest can be seen absorbers, which do not follow such reaction routes. Scheme 7 depicts a

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• (2S,1'S)-6 correspond to (S)- or ʟ-serinal (Figure 3) [13]. Furthermore, since the aziridine ring openings can be accomplished with other nucleophiles and the reductive cleavage is also known [14][15] the aziridines 5–8 offer a plethora of opportunities for enantioselective synthesis of structurally

• )-13 prepared from the respective esters (Scheme 4) 5b appeared moderately active as immunostimulants [18]. Amines and amino alcohols By functionalization at C2: Synthesis of enantiomerically pure amines from 2-substituted N-(1-phenylethyl)aziridines 5–7 requires a regioselective reductive aziridine

• to supply (R)-16 [42]. To synthesize (R)-17 the aminosulfonyl group was introduced in a standard way before hydrogenation [43]. The synthesis of amino alcohols of general formula 11 (Scheme 3) from 2-substituted N-(1-phenylethyl)aziridines 5 and 6 can be achieved by a regioselective reductive

Electrophilic oligodeoxynucleotide synthesis using dM-Dmoc for amino protection

• Shahien Shahsavari,
• Dhananjani N. A. M. Eriyagama,
• Bhaskar Halami,
• Vagarshak Begoyan,
• Marina Tanasova,
• Jinsen Chen and
• Shiyue Fang

Beilstein J. Org. Chem. 2019, 15, 1116–1128, doi:10.3762/bjoc.15.108

• protected with the 2-cyanoethyl group. These protecting groups and the linker have to be cleaved under strongly basic and nucleophilic conditions. As a result, many sensitive groups including acetal, hemiacetal, vinyl ethers, enol ethers, aldehydes, esters, activated esters, thioesters, aziridines, epoxides

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• addition to imines, aziridines were also amenable to the cobalt-catalyzed hydroarylation reaction (Scheme 36) [96]. Treatment of 2-phenylpyridines 3 with varies aryl-substituted aziridines gave 1,1-diarylethane derivatives 58 in a highly regioselective manner. It is noteworthy that nucleophilic addition

• took place selectively at the more hindered C-2 position of aziridines, which results in high regioselectivity. 5.2 Cobalt(III)-catalyzed hydroarylation of C=X bonds As the Co(III)Cp* catalyst acts an efficient air-stable catalyst for hydroarylation of the C=C bond, it would also provide a user

• . Co-catalyzed hydroarylative cyclization of enynes with carbonyl compounds. Mechanism for the Co-catalyzed hydroarylative cyclization of enynes with carbonyl compounds. Co-catalyzed addition of 2-arylpyridines to aromatic aldimines. Co-catalyzed addition of 2-arylpyridines to aziridines. Co(III

A general and atom-efficient continuous-flow approach to prepare amines, amides and imines via reactive N-chloramines

• Katherine E. Jolley,
• Michael R. Chapman and
• A. John Blacker

Beilstein J. Org. Chem. 2018, 14, 2220–2228, doi:10.3762/bjoc.14.196

• are known to react with N-haloamines to form aziridines and other N-heterocycles. Typically, the reactions require a catalyst (e.g., Cu, I2) [17][18][27], whilst more active reagents such as chloramine-T with osmate catalysts have been used to make 1,2-aminoalcohols and diamines [28][29][30][31][32

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• product was obtained in 72% yield after only 12 h which suggested the importance of water in the reaction. As shown in Scheme 3, various epoxides and aziridines underwent reaction with various thiols to give the corresponding ring-opened β-hydroxy products in moderate to good yield. The structure of the

• sulfide syntheses by ring opening of epoxides under different Lewis and Brønsted acid and base catalysts. n-Bu3P-catalyzed thiolysis of epoxides and aziridines to provide the corresponding β-hydroxy and β-amino sulfides. Zinc(II) chloride-mediated thiolysis of epoxides. Thiolysis of epoxides and one-pot