β-Amino functionalization of cinnamic Weinreb amides in ionic liquid

• Yi-Ning Wang,
• Guo-Xiang Sun and
• Gang Qi

Beilstein J. Org. Chem. 2016, 12, 2372–2377, doi:10.3762/bjoc.12.231

• corresponding to [PhCHNHNs]+ (m/z = 291) could be clearly observed. The results indicated that the isolated products were both α-chloro-β-amino Weinreb amide derivatives. The assignments for the stereoselectivities were determined by the conversions of the diastereomers to their corresponding aziridines (Scheme

•  3), and diastereomers 6a-A and 6a-B were chosen as representative substrates. Based on the vicinal Karplus correlation diagram, the vicinal proton coupling constants in the 1H NMR spectra of cis-aziridines are larger than those of trans-azridines [38][39]. In the 1H NMR spectra of the resulting

• aziridines derived from compounds 6a-A and 6a-B, the vicinal proton coupling constants were 7.5 Hz and 4.5 Hz, respectively. Therefore, compound 6a-A was assigned as syn-stereoisomer, and compound 6a-B was assigned as anti-stereoisomer. In the 1H NMR spectra of the isolated diastereomers, an obvious and

Three-component synthesis of highly functionalized aziridines containing a peptide side chain and their one-step transformation into β-functionalized α-ketoamides

• Lena Huck,
• Juan F. González,
• Elena de la Cuesta and
• J. Carlos Menéndez

Beilstein J. Org. Chem. 2016, 12, 1772–1777, doi:10.3762/bjoc.12.166

• -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. Keywords: α-ketoamides; aziridines; multicomponent reactions; nitrogen heterocycles; one-pot reactions; peptide mimics; vicinal tricarbonyl compounds; Introduction Aziridine

• moieties occur in many natural products and are also encountered in unnatural biologically active compounds including drugs in clinical use, especially in the field of cancer treatment [1]. In the areas of medicinal chemistry and chemical biology, aziridines are of current interest as starting materials

Investigation on the reactivity of α-azidochalcones with carboxylic acids: Formation of α-amido-1,3-diketones and highly substituted 2-(trifluoromethyl)oxazoles

• Kandasamy Rajaguru,
• Arumugam Mariappan,
• Rajendran Suresh,
• Periasamy Manivannan and
• Shanmugam Muthusubramanian

Beilstein J. Org. Chem. 2015, 11, 2021–2028, doi:10.3762/bjoc.11.219

• character of the C(2)–N double bond is higher than a normal imine (Figure 1) [10][26][27]. The generated substituted aziridines A2 may undergo further ring opening reactions. The α-azidochalcones 1 are suitable as precursors for the generation of 2H-azirines A1, though several other methods are available

Metal-free one-pot synthesis of 2-substituted and 2,3-disubstituted morpholines from aziridines

• Hongnan Sun,
• Binbin Huang,
• Run Lin,
• Chao Yang and
• Wujiong Xia

Beilstein J. Org. Chem. 2015, 11, 524–529, doi:10.3762/bjoc.11.59

• -substituted and 2,3-disubstituted morpholines through a one-pot strategy is described. A simple and inexpensive ammonium persulfate salt enables the reaction of aziridines with halogenated alcohols to proceed via an SN2-type ring opening followed by cyclization of the resulting haloalkoxy amine. Keywords

• intriguing strategy for the synthesis of substituted morpholines through Cu(OTf)2-catalyzed ring-opening/closing reactions of aziridines and halogenated alcohols in high yield and enantioselectivity (Scheme 1a) [21]. However, this method suffered from the need for transition metal catalysts and low

• temperatures in the initial stage. Thus, the discovery of an operationally simple and eco-friendly synthetic approach is a desirable complement to current methodologies. Recently we have reported the visible light-mediated ring opening of aziridines by a number of nucleophiles, such as LiBr, NaN3 and alcohols

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

Beilstein J. Org. Chem. 2014, 10, 2858–2873, doi:10.3762/bjoc.10.303

• flask at −78 °C still renders attractive results, addition of dienophile to 58 and vice versa leads to significantly lower yields. Due to the synthetic usefulness of aziridines, the aziridination of olefins is of particular interest for organic chemists [3]. The three-membered aziridine ring exhibits an

Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules

• Thilo Focken and
• Stephen Hanessian

Beilstein J. Org. Chem. 2014, 10, 1848–1877, doi:10.3762/bjoc.10.195

• acids 55 (Scheme 7) [59]. The synthesis of an mGluR agonist was achieved using chloromethyl phosphonamide 28d [60][61], as discussed later in this review. Replacing Michael acceptors with oximes in the reaction with chloroallyl phosphonamide 47a leads to the stereoselective formation of cis-aziridines

• synthesis of MMP-inhibitors [63], as discussed later in this review. Aziridines are also obtained as primary products in the addition of chloromethyl phosphonamide 28d to imines. The initial attack leads to a α-chloro-β-amino phosphonamide adduct as intermediate, which then undergoes intramolecular

• cyclization to form the aziridine ring after elimination of chloride. When N-substituted aromatic imines are used, the corresponding aziridines can be reduced at the benzylic carbon to give α-aminophosphonic acids [64]. Synthesis of phosphonamides There are four major methods for the synthesis of

One-pot stereoselective synthesis of α,β-differentiated diamino esters via the sequence of aminochlorination, aziridination and intermolecular S_N2 reaction

• Yiwen Xiong,
• Ping Qian,
• Chenhui Cao,
• Haibo Mei,
• Jianlin Han,
• Guigen Li and
• Yi Pan

Beilstein J. Org. Chem. 2014, 10, 1802–1807, doi:10.3762/bjoc.10.189

• product can be easily converted into aziridines [33][34] and α,β-dehydroamino acid derivatives [35] in the presence of an organic amine. Recently, we found that treating haloamine with benzylamine resulted in an unexpected α,β-diamino product, instead of the aziridine or the α,β-dehydroamino product

Rasta resin–triphenylphosphine oxides and their use as recyclable heterogeneous reagent precursors in halogenation reactions

• Xuanshu Xia and
• Patrick H. Toy

Beilstein J. Org. Chem. 2014, 10, 1397–1405, doi:10.3762/bjoc.10.143

• reagent precursors in a wide range of halogenation reactions. The rasta resin–triphenylphosphine oxides were reacted with either oxalyl chloride or oxalyl bromide to form the corresponding halophosphonium salts, and these in turn were reacted with alcohols, aldehydes, aziridines and epoxides to form

• reactions, such as those illustrated in Scheme 2: (1) the conversion of alcohols 4 to alkyl halides 5 (the Appel reaction), (2) the conversion of aldehydes 6 to 1,1-dihaloalkanes 7, (3) halogenation of aziridines 8 to form 2-haloamines 9, (4) halogenation of epoxides 10 to form 1,2-dihaloalkanes 11, (5) and

• and 17b in aziridine halogenation reactions [34]. Using reaction conditions similar to those used for the Appel and aldehyde halogenation reactions, a variety of N-tosyl aziridines 8 were successfully converted into the corresponding chloro- or bromotosylamides 9 in excellent yields (Table 3). The

Synthesis of chiral N-phosphoryl aziridines through enantioselective aziridination of alkenes with phosphoryl azide via Co(II)-based metalloradical catalysis

• Jingran Tao,
• Li-Mei Jin and
• X. Peter Zhang

Beilstein J. Org. Chem. 2014, 10, 1282–1289, doi:10.3762/bjoc.10.129

• ; cobalt complex; metalloradical catalysis; organophosphorus; phosphoryl azide; Introduction Aziridines, the smallest three-membered nitrogen-containing heterocycles, are highly valuable heterocyclic compounds that are widely used in organic synthesis and pharmaceuticals [1][2]. As a result, tremendous

• alkenes and nitrene sources [9][10][11][12]. The enantioselective olefin aziridination is of particular significance due to the streamlined approach for the installation of chiral aziridines, which are versatile intermediates in organic synthesis. To date, several different types of transition metal-based

• -containing aziridines, producing nitrogen gas as the only and also environmentally friendly byproduct. Chiral phosphorylated aziridines and their derivatives have been demonstrated with pharmaceutical and other important synthetic applications. In addition to the fundamental and practical significance of the

Site-selective covalent functionalization at interior carbon atoms and on the rim of circumtrindene, a C₃₆H₁₂ open geodesic polyarene

• Hee Yeon Cho,
• Ronald B. M. Ansems and
• Lawrence T. Scott

Beilstein J. Org. Chem. 2014, 10, 956–968, doi:10.3762/bjoc.10.94

• ] cycloadditions, the reaction with azomethine ylides has found great popularity, because it leads to versatile pyrrolidine derivatives of C60. The sources of the ylide can be iminium salts, aziridines, oxazolidines or silylated iminium compounds. In 1993, Prato and coworkers developed the protocol that is now

Stereoselectively fluorinated N-heterocycles: a brief survey

• Xiang-Guo Hu and
• Luke Hunter

Beilstein J. Org. Chem. 2013, 9, 2696–2708, doi:10.3762/bjoc.9.306

• aziridines. Aziridines (1, Figure 1) are generally very stable, in marked contrast with their oxygenated counterparts, the epoxides. However, if one or two fluorine atoms are attached to the aziridine backbone, the resulting molecule is much more susceptible to hydrolysis. De Kimpe and co-workers have

• favour nucleophilic ring opening at C3 [17], preliminary experiments showed that the mono- and difluorinated aziridines actually behave differently in the presence of nucleophiles, with monofluorinated aziridines 2 experiencing C2 attack and the difluorinated counterparts 3 favouring C3 attack

• from fluorine-containing organic building blocks. Such an approach benefits from the wide variety, and frequently the low cost, of today’s commercially available organofluorine molecules [63][64]. For example, the fluorinated aziridines 2 and 3 presented earlier (Figure 1) were synthesised through a

Organocatalyzed enantioselective desymmetrization of aziridines and epoxides

• Ping-An Wang

Beilstein J. Org. Chem. 2013, 9, 1677–1695, doi:10.3762/bjoc.9.192

• Ping-An Wang Department of Medicinal Chemistry, School of Pharmacy, Fourth Military Medical University, Changle Xilu 17, Xi-An, 710032, P. R. China 10.3762/bjoc.9.192 Abstract Enantioselective desymmetrization of meso-aziridines and meso-epoxides with various nucleophiles by organocatalysis has

• emerged as a cutting-edge approach in recent years. This review summarizes the origin and recent developments of enantioselective desymmetrization of meso-aziridines and meso-epoxides in the presence of organocatalysts. Keywords: aziridine; desymmetrization; enantioselectivity; epoxide; organocatalysis

• compounds from readily available achiral substrates. The past decade witnessed the renaissance and the golden age of organocatalyzed reactions [7][8][9]. Aziridines and epoxides are quite reactive due to the large tension of their three-membered ring system. The enantioselective ring-opening of aziridines

Preparation and ring-opening reactions of N-diphenylphosphinyl vinyl aziridines

• Ashley N. Jarvis,
• Andrew B. McLaren,
• Helen M. I. Osborn and
• Joseph Sweeney

Beilstein J. Org. Chem. 2013, 9, 852–859, doi:10.3762/bjoc.9.98

• -diphenylphosphinyl vinyl aziridines are prepared by a reaction of N-diphenylphosphinyl imines with α-bromoallyllithium in the presence of freshly fused ZnCl2. These aziridines undergo a ring-opening reaction with a variety of carbon and heteronucleophiles, in good yield, and generally with good regioselectivity

• . Keywords: aziridines; catalytic; heterocycles; palladium; ring opening; Introduction Vinyl aziridines are useful molecules that have attracted the attention of synthetic chemists for many years. These strained bifunctional heterocycles possess considerable synthetic flexibility and undergo a range of

• efficient transformations [1][2][3][4][5][6][7][8][9]. Whilst there has been a recent resurgence in the development of reactions using vinyl aziridines, there have been few contemporary reports of new methods for their synthesis [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

• in 7 (n = 1) is replaced by a heteroatom, the heteroorganic bisallenes 16 result, in their simplest form as ethers (X = O), amines (X = NR), thioethers (X = S), etc. Analogously bisallenic epoxides (17, X = O) or aziridines (17, X = NR) can formally be generated from the corresponding all-carbon

Synthesis and ring openings of cinnamate-derived N-unfunctionalised aziridines

• Alan Armstrong and
• Alexandra Ferguson

Beilstein J. Org. Chem. 2012, 8, 1747–1752, doi:10.3762/bjoc.8.199

• -diphenylphosphinyl hydroxylamine. The resulting N-unfunctionalised aziridines are shown to be versatile synthetic building blocks that undergo highly selective ring-opening reactions with a wide range of nucleophiles. Keywords: amino acids; aziridination; organocatalysis; ring opening; stereoselectivity

• -carboxylate (Scheme 1) [2][3]. Such a methodology has been developed for N-functionalised aziridines [4][5][6][7][8][9], as N-functionality offers both activation of the aziridine to ring opening [10], and protection of the nitrogen. However, an extra synthetic step may be required to remove the N

• -functionality, which is often difficult and low yielding [11][12][13][14][15]. Ring opening of N-unfunctionalised (NH-) aziridines allows direct access to amino-acid derivatives, yet the published methodology is currently limited for this transformation [16][17][18][19][20]. In literature examples where ring

Synthesis of 2-amino-3-arylpropan-1-ols and 1-(2,3-diaminopropyl)-1,2,3-triazoles and evaluation of their antimalarial activity

• Matthias D’hooghe,
• Stéphanie Vandekerckhove,
• Karen Mollet,
• Karel Vervisch,
• Stijn Dekeukeleire,
• Liesbeth Lehoucq,
• Carmen Lategan,
• Peter J. Smith,
• Kelly Chibale and
• Norbert De Kimpe

Beilstein J. Org. Chem. 2011, 7, 1745–1752, doi:10.3762/bjoc.7.205

• variety of 2-amino-3-arylpropan-1-ols, anti-2-amino-3-aryl-3-methoxypropan-1-ols and anti-2-amino-1-arylpropan-1,3-diols were prepared selectively through elaboration of trans-4-aryl-3-chloro-β-lactams. In addition, a number of 2-(azidomethyl)aziridines was converted into novel 2-[(1,2,3-triazol-1-yl

• )methyl]aziridines by Cu(I)-catalyzed azide-alkyne cycloaddition, followed by microwave-assisted, regioselective ring opening by dialkylamine towards 1-(2,3-diaminopropyl)-1,2,3-triazoles. Although most of these compounds exhibited weak antiplasmodial activity, six representatives showed moderate

• antiplasmodial activity against both a chloroquine-sensitive and a chloroquine-resistant strain of Plasmodium falciparum with IC50-values of ≤25 μM. Keywords: aminopropanes; antimalarial activity; aziridines; β-lactams; ring opening; Introduction Malaria remains a major issue in health control, especially in

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• the pyrazolidinone generally provides the bicyclic product 166 with high cis selectivity, which is determined during ring closing rather than in the formation of allyl–gold intermediate [76]. Gold-catalyzed cycloisomerization reaction of alkynyl aziridines 167 can give 2,5-disubstituted pyrroles 168

• in high yields [77]. However, in some cases, aryl-substituted N-tosyl alkynyl aziridines 169 undergo a gold-catalyzed ring expansion to afford 2,5-substituted or 2,4-substituted pyrrole products [78]. Interestingly, the reaction pathway is determined by the counter ion of the gold catalyst. The

• pyrroles 173 by gold-catalyzed ring expansion of alkynyl aziridines 172 [79]. In this study a combination of Ph3PAuCl and AgOTs generates a catalyst system that provides clean cycloisomerisation reactions. Similarly, N-Phth pyrrroles 175 are obtained via gold-catalyzed cycloisomerization of N-Phth alkynyl

Isotopic labelling studies for a gold-catalysed skeletal rearrangement of alkynyl aziridines

• Paul W. Davies,
• Nicolas Martin and
• Neil Spencer

Beilstein J. Org. Chem. 2011, 7, 839–846, doi:10.3762/bjoc.7.96

• aziridines into 2,4-disubstituted pyrroles. Two isotopomers of the expected skeletal rearrangement product were identified using 13C-labelling and led to a revised mechanism featuring two distinct skeletal rearrangements. The mechanistic proposal has been rationalised against the reaction of a range of 13C

• 1,2-alkyl migrations are well-established in gold-catalysed heterocyclic synthesis [12][13], 1,2-aryl shifts are much less common [14][15][16][17]. In relation to these processes, we recently reported the gold-catalysed reactions of aryl substituted alkynyl aziridines, such as 1. Careful choice of

• afford the desired cycloisomerisation precursor 4 [28]. The aziridines were formed as a mixture of diastereomers, with the cis diastereomer predominating, and were employed as such in the cycloisomerisation reactions. Deuterated aziridine 4 was reacted under the standard conditions for skeletal

Synthesis of novel 5-alkyl/aryl/heteroaryl substituted diethyl 3,4-dihydro-2H-pyrrole-4,4-dicarboxylates by aziridine ring expansion of 2-[(aziridin-1-yl)-1-alkyl/aryl/heteroaryl-methylene]malonic acid diethyl esters

• Satish S. More,
• T. Krishna Mohan,
• Y. Sateesh Kumar,
• U. K. Syam Kumar and
• Navin B. Patel

Beilstein J. Org. Chem. 2011, 7, 831–838, doi:10.3762/bjoc.7.95

• -[(aziridin-1-yl)-1-alkyl/aryl/heteroaryl-methylene]malonic acid diethyl esters in very good to excellent yields under mild reaction conditions. The electronic and steric impact of the substituents on the kinetics of ring expansion of N-vinyl aziridines to pyrrolines has been studied. Various diversely

• -vinyl substituted aziridines; ring expansion; sodium iodide; Introduction Vinylaziridines are a particularly interesting class of aziridine derivatives that lend themselves to a host of highly useful synthetic transformations [1]. They are versatile electrophiles and notably undergo regioselective ring

• chemistry and new applications of these compounds are being continuously explored [10][11][12][13][14][15][16][17][18][19][20][21][22]. However, not much attention has been paid to N-vinyl substituted aziridines. Thus, N-vinyl substituted aziridines provide an opportunity for researchers to explore their

Synthetic applications of gold-catalyzed ring expansions

• David Garayalde and
• Cristina Nevado

Beilstein J. Org. Chem. 2011, 7, 767–780, doi:10.3762/bjoc.7.87

• gold-catalyzed ring expansion of 1-oxiranyl-1-alkynylcyclopropanes [43][44]. An alternative method for obtaining disubstituted pyrroles via gold-catalyzed ring expansion was reported by Davies and co-workers who employed alkynyl aziridines 51 as intramolecular nucleophiles [45]. Ring expansion from the

• aziridines onto the adjacent alkyne afforded the 2,5-disubstituted pyrroles 52 in high yields (Scheme 16). In 2011, Barluenga et al. developed a new methodology for the preparation of 1,6-disubstituted regioisomeric cyclohexadienes 54 and 54' (Scheme 17) [46]. The process resulted in a five-to-six-membered

• aziridines. Gold-catalyzed synthesis of disubstituted cyclohexadienes. Gold-catalyzed synthesis of indenes. Gold-catalyzed [n + m] annulation processes. Gold-catalyzed generation of 1,4-dipoles. Gold-catalyzed synthesis of repraesentin F. Gold-catalyzed ring expansion of cyclopropyl 1,6-enynes. Gold

α,β-Aziridinylphosphonates by lithium amide-induced phosphonyl migration from nitrogen to carbon in terminal aziridines

• David. M. Hodgson and
• Zhaoqing Xu

Beilstein J. Org. Chem. 2010, 6, 978–983, doi:10.3762/bjoc.6.110

• David. M. Hodgson Zhaoqing Xu Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, UK, Fax: +44(1865) 285002 10.3762/bjoc.6.110 Abstract N-Phosphonate terminal aziridines undergo lithium 2,2,6,6-tetramethylpiperidide-induced N- to C-[1,2

• acids; aziridines; lithiation; migration; synthetic methods; Introduction The synthesis of aminophosphonic acids and their derivatives has attracted considerable attention, since the presence of such functionality, typically as amino acid surrogates, leads to interesting bioactivity in, for example

• our investigations [9][10][11][12][13] on the generation and subsequent chemistry of α-lithiated terminal aziridines [14], we considered whether α,β-aziridinylphosphonates 3 could be accessed by α-lithiation of N-phosphonate terminal aziridines 1, followed by N- to C-[1,2]-anionic phosphonyl group

Palladium- catalyzed cross coupling reactions of 4-bromo- 6H-1,2-oxazines

• Reinhold Zimmer,
• Elmar Schmidt,
• Michal Andrä,
• Marcel-Antoine Duhs,
• Igor Linder and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2009, 5, No. 44, doi:10.3762/bjoc.5.44

• alcohols [20], aziridines [21], pyrrolizidines [22], and pyrrolidine derivatives [15][23][24]. In the context of our ongoing exploration of the synthetic potential of these heterocycles we were interested to modify the substitution pattern of the C-4,C-5 double bond of 6H-1,2-oxazines [25][26][27]. Herein

The enantiospecific synthesis of (+)-monomorine I using a 5-endo- trig cyclisation strategy

• Malcolm B. Berry,
• Donald Craig,
• Philip S. Jones and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2007, 3, No. 39, doi:10.1186/1860-5397-3-39

• mode of cyclisation. [1][2][3][4][5][6] The methodology allows the conversion of epoxides (X = O) or aziridines (X = N-PG) (2) into the desired trisubstituted tetrahydrofurans or pyrrolidines (5) via a series of sulfone-mediated transformations (Scheme 1). Ring-opening 2 with the sulfone-stabilised

Pd-catalysed [3 + 3] annelations in the stereoselective synthesis of indolizidines

• Olivier Y. Provoost,
• Andrew J. Hazelwood and
• Joseph P. A. Harrity

Beilstein J. Org. Chem. 2007, 3, No. 8, doi:10.1186/1860-5397-3-8

• + 3] annelation of aziridines and Trost's conjunctive allylsilane reagent. We have also found that reduction of the lactam unit of 11 and acetylation of the hydroxyl group takes place smoothly to provide 13, demonstrating the potential of these intermediates for the synthesis of slaframine and related