Rapid access to the core of malayamycin A by intramolecular dipolar cycloaddition

• Yilin Liu,
• Yuchen Yang,
• Chen Yang,
• Sha-Hua Huang,
• Jian Jin and
• Ran Hong

Beilstein J. Org. Chem. 2025, 21, 2542–2547, doi:10.3762/bjoc.21.196

• of Sciences, 345 Lingling Road, Shanghai 200032, P.R. China 10.3762/bjoc.21.196 Abstract We have streamlined a dipolar cycloaddition approach to assemble the core of malayamycin A and other related uracil nucleosides possessing the common bicyclic perhydrofuropyran framework. The latent

• development of potent fungicides. Keywords: dipolar cycloaddition; elimination; fungicide; nucleoside; oxazoline; Introduction Modern agriculture relies on various effective fungicides to combat crop diseases for achieving significant gains [1]. However, the long-term and widespread use of chemicals and

• monosaccharides and applying dipolar cycloaddition to construct various bioactive compounds [21][22][23][24][25][26][27], we intended to develop a practical strategy to access the perhydrofuropyran core of malayamycin A and other uracil nucleosides to enable future rapid derivatization (Scheme 1B). The bicyclic

The high potential of methyl laurate as a recyclable competitor to conventional toxic solvents in [3 + 2] cycloaddition reactions

• Ayhan Yıldırım and
• Mustafa Göker

Beilstein J. Org. Chem. 2025, 21, 2389–2415, doi:10.3762/bjoc.21.184

• ) between the phenyl rings substituted on the nitrogen atoms of both maleimide and nitrone [109]. The most significant evidence confirming the interactions that determine the diastereoselectivity observed here is that the cis diastereomer is the major addition product in the dipolar cycloaddition reaction

Electrochemical cyclization of alkynes to construct five-membered nitrogen-heterocyclic rings

• Lifen Peng,
• Ting Wang,
• Zhiwen Yuan,
• Bin Li,
• Zilong Tang,
• Xirong Liu,
• Hui Li,
• Guofang Jiang,
• Chunling Zeng,
• Henry N. C. Wong and
• Xiao-Shui Peng

Beilstein J. Org. Chem. 2025, 21, 2173–2201, doi:10.3762/bjoc.21.166

• for this reaction was proposed. Firstly, oxidation of I− at the anode afforded I•, which abstracted a hydrogen atom from 50a to form the intermediate A with elimination of HI as a by-product. The second abstraction of a hydrogen atom generated ketone B, which then underwent 1,3-dipolar cycloaddition

C2 to C6 biobased carbonyl platforms for fine chemistry

• Jingjing Jiang,
• Muhammad Noman Haider Tariq,
• Florence Popowycz,
• Yanlong Gu and
• Yves Queneau

Beilstein J. Org. Chem. 2025, 21, 2103–2172, doi:10.3762/bjoc.21.165

The application of desymmetric enantioselective reduction of cyclic 1,3-dicarbonyl compounds in the total synthesis of terpenoid and alkaloid natural products

• Dong-Xing Tan and
• Fu-She Han

Beilstein J. Org. Chem. 2025, 21, 2085–2102, doi:10.3762/bjoc.21.164

• operation including azide–alkene dipolar cycloaddition, irradiation of the resulting triazoline to aziridine 80 and in situ ring opening followed by deacetylation achieved the first total synthesis of (−)-hunterine A (14). On the other hand, aza-Cope/Mannich reaction of 78 produced imine intermediate 81

Preparation of spirocyclic oxindoles by cyclisation of an oxime to a nitrone and dipolar cycloaddition

• Beth L. Ritchie,
• Alexandra Longcake and
• Iain Coldham

Beilstein J. Org. Chem. 2025, 21, 1890–1896, doi:10.3762/bjoc.21.146

• -containing compounds makes use of intramolecular 1,3-dipolar cycloaddition reactions [15], including examples with nitrone ylides [16][17][18][19][20][21][22]. Our research group has exploited this approach for the synthesis of alkaloids such as myrioxazine A and aspidospermidine [23][24]. With a nitrone 1,3

• that can be explored for its ability to undergo dipolar cycloaddition chemistry. Results and Discussion The oxindole core was prepared from isatin following known chemistry to give the spirocyclic epoxide 1 (Scheme 2) [28]. This was subjected to regioselective ring-opening with allyltrimethylsilane in

• aldehyde 4 could now be tested in the cascade chemistry. This entails the addition of hydroxylamine to form the oxime, followed by cyclisation (with displacement of the tosylate) to give the nitrone for the desired dipolar cycloaddition reaction. Related chemistry (without the oxindole) with a halide

Transition-state aromaticity and its relationship with reactivity in pericyclic reactions

• Israel Fernández

Beilstein J. Org. Chem. 2025, 21, 1613–1626, doi:10.3762/bjoc.21.125

• computed lower strain energy and ultimately into the lower barrier. 1,3-Dipolar cycloaddition reactions between azides and metal cyaphide complexes Similar to the Diels–Alder cycloaddition reaction, the 1,3-dipolar cycloaddition between a 1,3-dipole (acting as 4π system) and a 2π dipolarophile is a widely

• , very recently it was found that the C≡P moiety, in particular, can be stabilized in the form of a cyaphide ligand bonded to a metal fragment [99][100]. These cyaphide complexes are proven to readily undergo 1,3-dipolar cycloaddition reactions with organic azides [99][100][101], affording novel metal

• of the NICS(3, +1) values along a z-axis perpendicular to the molecular plane of the TSs involved in the 1,3-dipolar cycloaddition reactions between t-BuN3 and cyaphide complexes. Comparative activation strain analyses (a) and energy decomposition analysis (b) of the 1,3-dipolar cycloaddition

Facile synthesis of hydantoin/1,2,4-oxadiazoline spiro-compounds via 1,3-dipolar cycloaddition of nitrile oxides to 5-iminohydantoins

• Juliana V. Petrova,
• Varvara T. Tkachenko,
• Victor A. Tafeenko,
• Anna S. Pestretsova,
• Vadim S. Pokrovsky,
• Maxim E. Kukushkin and
• Elena K. Beloglazkina

Beilstein J. Org. Chem. 2025, 21, 1552–1560, doi:10.3762/bjoc.21.118

• -oxadiazoline spiro-compounds using a 1,3-dipolar cycloaddition of nitrile oxides to C=N bonds of 5-iminohydantoins. The efficiency of the approach was demonstrated by varying the substituents at four positions of the resulting spirocyclic molecules. Cytotoxicity of the target hydantoin/1,2,4-oxadiazolines was

• shown to exceed previously known spiro-compounds bearing only hydantoins or 1,2,4-oxadiazolines (IC50 values were 30–50 μM, HCT116 cell lines). Keywords: 1,3-dipolar cycloaddition; hydantoins; nitrile oxides; Shiff bases; spiro-compounds; Introduction The 1,2,4-oxadiazole fragment is a common

• dipolarophiles into the 32CA, it is reasonable to utilize conditions that minimize the side reactions of the dipole. This could include lowering the temperature [32] and slowly adding a base [33]. In this work we have tested two alternative techniques for the dipolar cycloaddition. In the first method, a

Oxetanes: formation, reactivity and total syntheses of natural products

• Peter Gabko,
• Martin Kalník and
• Maroš Bella

Beilstein J. Org. Chem. 2025, 21, 1324–1373, doi:10.3762/bjoc.21.101

Three-component reactions of conjugated dienes, CH acids and formaldehyde under diffusion mixing conditions

• Dmitry E. Shybanov,
• Maxim E. Kukushkin,
• Eugene V. Babaev,
• Nikolai V. Zyk and
• Elena K. Beloglazkina

Beilstein J. Org. Chem. 2025, 21, 262–269, doi:10.3762/bjoc.21.18

• method was successfully used to generate highly active nitrile oxides and nitrilimines for 1,3-dipolar cycloaddition reactions [19][20][21]. Based on our previous experience with diffusion mixing, we assumed that formaldehyde vapor diffusion into the reaction would lead to an extremely low concentration

Multicomponent reactions driving the discovery and optimization of agents targeting central nervous system pathologies

• Lucía Campos-Prieto,
• Aitor García-Rey,
• Eddy Sotelo and
• Ana Mallo-Abreu

Beilstein J. Org. Chem. 2024, 20, 3151–3173, doi:10.3762/bjoc.20.261

• years, the Ugi reaction has emerged as a highly considered reaction due to its mild conditions, broad applications, and product diversity. It enables the selective assembly of precursors, facilitating various post-reaction transformations such as deprotection cyclization, 1,3-dipolar cycloaddition, and

Synthesis of pyrrole-fused dibenzoxazepine/dibenzothiazepine/triazolobenzodiazepine derivatives via isocyanide-based multicomponent reactions

• Marzieh Norouzi,
• Mohammad Taghi Nazeri,
• Ahmad Shaabani and
• Behrouz Notash

Beilstein J. Org. Chem. 2024, 20, 2870–2882, doi:10.3762/bjoc.20.241

• with 1,10-phenanthroline as cyclic imine under solvent-free conditions for the synthesis of pyrrole-fused phenanthroline. This reaction proceeds via in situ formation of zwitterion I through reaction of the aldehyde and malononitrile followed by 1,3-dipolar cycloaddition (Scheme 1a) [41]. Chen and co

Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

• formed in situ from aromatic aldehydes and tosylhydrazine. After basic treatment of these tosylhydrazones followed by 1,3-dipolar cycloaddition with terminal alkynes, the corresponding pyrazoles 168 are obtained. The regioselectivity of this synthesis can be explained by steric causes and the favored

• HOMO (diazo compound)–LUMO (alkyne) interaction during the 1,3-dipolar cycloaddition [163], Wu et al. showed that electronic effects in this strategy do not influence the yield. In addition, sterically demanding reactants could be used in the method. Enhanced yields were achieved by using NaOEt and

• applied to synthesize 3,4,5-substituted pyrazoles 173 and 174 via 1,3-dipolar cycloaddition of in situ generated diazo compounds and vinylidenecyclopropane diesters 172, which are synthetic equivalents of alkynes (Scheme 58) [176]. Notably, employing aromatic vinylidenecyclopropane diesters (R2 = aryl) in

Syntheses and medicinal chemistry of spiro heterocyclic steroids

• Laura L. Romero-Hernández,
• Ana Isabel Ahuja-Casarín,
• Penélope Merino-Montiel,
• Sara Montiel-Smith,
• José Luis Vega-Báez and
• Jesús Sandoval-Ramírez

Beilstein J. Org. Chem. 2024, 20, 1713–1745, doi:10.3762/bjoc.20.152

• , such as a one-pot four-component synthesis and the use of ionic liquids as solvents [30]. Kanchithalaivan et al. [31] reported a library of 16-spiro pyrrolo[1,2-c][1,3]thiazoles of trans-androsterone and DHEA (49a and 49b, respectively). The syntheses were achieved through the 1,3-dipolar cycloaddition

• starting material (35%). 16-Spiropyrazoline steroids In 2009 Mernyák et al. described the synthesis of 16-spiropyrazolines from 16-methylene-13α-estrone derivatives via a 1,3-dipolar cycloaddition reaction between the methylene of α,β-unsaturated ketones 53a,b and the ylide produced from the

• superior results compared to phenyl-substituted compounds. Frank et al. synthesized a series of 16-spiroisoxazolines through a regio- and a highly stereoselective 1,3-dipolar cycloaddition between the double bond of the α,β-unsaturated steroidal ketone 73 and various arylnitrile oxides [45]. The reaction

Rapid construction of tricyclic tetrahydrocyclopenta[4,5]pyrrolo[2,3-b]pyridine via isocyanide-based multicomponent reaction

• Xiu-Yu Chen,
• Ying Han,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2024, 20, 1436–1443, doi:10.3762/bjoc.20.126

• the amide anion in intermediate D afforded the final product 4 or 6. On the other hand, the final product 4 or 6 might be directly produced by dipolar cycloaddition reaction of 5-(alkylimino)cyclopenta-1,3-diene intermediate C with 5,6-unsaturated dihydropyridine. In consideration of the high

Trifluoromethylated hydrazones and acylhydrazones as potent nitrogen-containing fluorinated building blocks

• Zhang Dongxu

Beilstein J. Org. Chem. 2023, 19, 1741–1754, doi:10.3762/bjoc.19.127

• other derivatives in good yields [37] (Scheme 1). Later, Wu et al. described a diastereoselective 1,3-dipolar cycloaddition of trifluoroacetaldehyde hydrazones with α,β-ethenyl ketones to obtain polysubstituted pyrazolidines and pyrazolines. These reactions were carried out under two different sets of

Decarboxylative 1,3-dipolar cycloaddition of amino acids for the synthesis of heterocyclic compounds

• Xiaofeng Zhang,
• Xiaoming Ma and
• Wei Zhang

Beilstein J. Org. Chem. 2023, 19, 1677–1693, doi:10.3762/bjoc.19.123

• -stabilized azomethine ylide; Introduction The 1,3-dipolar cycloaddition of azomethine ylides (AMYs) [1][2][3][4][5][6] is a powerful method for the synthesis of bioactive pyrrolidine-containing compounds and natural product analogs [7][8][9][10][11][12][13][14][15]. AMYs generated from the reaction of

• AMYs B1 which then were reacted with nucleophiles to form C–H-functionalized pyrrolidines or subjected to the 1,3-dipolar cycloaddition with olefins to afford bicyclic compounds (Scheme 2A and B) [59][60]. We employed cyclic amines for the synthesis of spirooxindole-pyrrolidines 7a or 7b in good

• -oriented synthesis (DOS) [82][83][84][85][86][87][88]. The work presented in this paper may also be helpful to understand the reaction mechanism and stereoselectivity of semi-stabilized N–H-type AMYs. We hope the new development for 1,3-dipolar cycloaddition chemistry can be used for the synthesis of

Lewis acid-promoted direct synthesis of isoxazole derivatives

• Dengxu Qiu,
• Chenhui Jiang,
• Pan Gao and
• Yu Yuan

Beilstein J. Org. Chem. 2023, 19, 1562–1567, doi:10.3762/bjoc.19.113

• oxide E [23], which can be converted to the desired isoxazole with 1a through a 1,3-dipolar cycloaddition. Conclusion In conclusion, we have developed an efficient and concise synthesis of isoxazole nitrogen heterocycles by direct C–H-bond activation of methyl heteroaromatics. The method avoids using

Morpholine-mediated defluorinative cycloaddition of gem-difluoroalkenes and organic azides

• Tzu-Yu Huang,
• Mario Djugovski,
• Sweta Adhikari,
• Destinee L. Manning and
• Sudeshna Roy

Beilstein J. Org. Chem. 2023, 19, 1545–1554, doi:10.3762/bjoc.19.111

• -difluoroalkenes that subsequently undergoes a cycloaddition reaction. Results and Discussion While investigating 1,3-dipolar cycloaddition reactions between organic azides and gem-difluoroalkenes to obtain the 4-fluoro-1,4-disubstituted 1,2,3-triazole regioisomers, we observed an interesting reactivity while

Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• 1,3-dipolar cycloaddition and belongs to the general category of [π4s + π2s] cycloadditions. It is an important method to construct a five-membered heterocyclic ring [66]. As discussed earlier, the Cu atom in NHC–Cu(I) complexes has nucleophilic character, which allows binding to the positive end of

One-pot nucleophilic substitution–double click reactions of biazides leading to functionalized bis(1,2,3-triazole) derivatives

• Hans-Ulrich Reissig and
• Fei Yu

Beilstein J. Org. Chem. 2023, 19, 1399–1407, doi:10.3762/bjoc.19.101

• ]). Mechanistic aspects of the CuAAC have been studied in detail [16][17]. Whereas the traditional 1,3-dipolar cycloaddition (Huisgen reaction) [18][19][20] of azides and alkynes requires often – but not always – relatively harsh conditions and proceeds with moderate regioselectivity only [21], the copper

The unique reactivity of 5,6-unsubstituted 1,4-dihydropyridine in the Huisgen 1,4-diploar cycloaddition and formal [2 + 2] cycloaddition

• Xiu-Yu Chen,
• Hui Zheng,
• Ying Han,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2023, 19, 982–990, doi:10.3762/bjoc.19.73

• ; isoquinolino[1,2-f][1,6]naphthyridine; Introduction Among various well-known cycloaddition reactions such as the 1,3-dipolar cycloaddition reaction, Diels–Alder reaction, and the Povarov reaction, the cycloaddition reaction of Huisgen 1,4-dipoles with activated alkenes received increasing attention [1][2][3

Computational studies of Brønsted acid-catalyzed transannular cycloadditions of cycloalkenone hydrazones

• Manuel Pedrón,
• Jana Sendra,
• Irene Ginés,
• Tomás Tejero,
• Jose L. Vicario and
• Pedro Merino

Beilstein J. Org. Chem. 2023, 19, 477–486, doi:10.3762/bjoc.19.37

• common reaction conditions. The reaction has been defined by Houk and Rueping as a (3+ + 2) monopolar cycloaddition [33] pointing out the protonated state of the imino nitrogen of the hydrazone in contrast to the well-known 1,3-dipolar cycloaddition of azomethine imines in which the terminal nitrogen has

CuAAC-inspired synthesis of 1,2,3-triazole-bridged porphyrin conjugates: an overview

• Dileep Kumar Singh

Beilstein J. Org. Chem. 2023, 19, 349–379, doi:10.3762/bjoc.19.29

• -dipolar cycloaddition reaction between an azide and a terminal alkyne, also popular as "click reaction" or CuAAC reaction. Moreover, the 1,2,3-triazole ring also serves as a spacer and an electron transfer bridge between the porphyrin and the attached chromophores. In order to provide a critical overview

• of the synthesis and properties of various porphyrin-triazole hybrids, this review will discuss some of the key reactions involved in the preparation of triazole-linked porphyrin conjugates. Keywords: azide–alkyne; click chemistry; CuAAC; 1,3-dipolar cycloaddition; porphyrin; 1,2,3-triazole

• connect a porphyrin with a chromophoric group. Among these, the copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction [1][2] of azides with terminal alkynes is a popular and well established process to link a porphyrin with other moieties via 1,2,3-triazole group [3] (Figure 1). The term “click

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23