Synthesis of heterocycles based on azomethine ylides from α-amino acids (or amines) and carbonyl compounds

• Ekaterina V. Berezhnaya,
• Alexander I. Ponyaev,
• Vitali M. Boitsov and
• Alexander V. Stepakov

Beilstein J. Org. Chem. 2026, 22, 705–741, doi:10.3762/bjoc.22.55

• aromatic ring, as well as heterosubstituted alkenes and polyenes, are also known [30][31][32]. The review [33] examines the reactions of 1,3-dipolar cycloaddition of cyclopropenes with various dipoles, such as diazo compounds, azides, azomethine imines, nitrones, azomethine ylides, carbonyl ylides, etc. At

Synthesis of photo- and ionochromic N-acylated 2-(aminomethylene)benzo[b]thiophene-3(2Н)-ones with a terminal phenanthroline group

• Vladimir P. Rybalkin,
• Sofiya Yu. Zmeeva,
• Lidiya L. Popova,
• Irina V. Dubonosova,
• Olga Yu. Karlutova,
• Oleg P. Demidov,
• Alexander D. Dubonosov and
• Vladimir A. Bren

Beilstein J. Org. Chem. 2024, 20, 552–560, doi:10.3762/bjoc.20.47

• inverse photochromism), such as merocyanine forms of spiropyrans and spirooxazines, azomethine imines, thioindigoid dyes and N→O acylotropic systems [12][13][14][15]. Recently, they have been actively used to create next-generation molecular switches, materials with new properties (in particular, color

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

• . Hydrazones can be regarded as electrophilic and nucleophilic imine equivalents, and thus they represent valuable and versatile building blocks in synthetic chemistry [32][33][34][35][36]. Trifluoroacetaldehyde hydrazones can be regarded as an equivalent of fluorine-containing azomethine imines in the

• under basic conditions, and expanded the synthetic method to N-substituted acylhydrazones [106][107] (Scheme 18). In the early development of 1,3-dipolar cycloadditions of azomethine imines, the acyclic azomethine imines were unstable and their in situ preparation required Brønsted acid or thermal

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

• inversion of the reagents and whereas in the classical cycloadditions with azomethine imines, they act as a nucleophile (involving their HOMO, interacting with the LUMO of the alkene), in our case, the protonated hydrazone acts as an electrophile (involving their LUMO, interacting now with the HOMO of the

• alkene) (Figure 2). Thus, we can consider the reaction of hydrazones with alkenes an inverse-demand cycloaddition with respect to that of azomethine imines (Figure 2). In fact, we monitored the global electron density transfer (GEDT) [34] between the reagents along the reaction coordinate (Figure 3) and

Facile and innovative catalytic protocol for intramolecular Friedel–Crafts cyclization of Morita–Baylis–Hillman adducts: Synergistic combination of chiral (salen)chromium(III)/BF₃·OEt₂ catalysis

• Karthikeyan Soundararajan,
• Helen Ratna Monica Jeyarajan,
• Raju Subimol Kamarajapurathu and
• Karthik Krishna Kumar Ayyanoth

Beilstein J. Org. Chem. 2021, 17, 2186–2193, doi:10.3762/bjoc.17.140

• reaction at a yield of 61% and 72%, respectively. Encouraged by the outcome of this non-catalytic cycloaddition reaction, similar studies using 2-substituted-1H-indenes (6a–f) with azomethine imines are underway. Conclusion In summary we have developed an efficient synthetic protocol for intramolecular

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

• reaction undergo cycloreversion under the reaction conditions. Keywords: azomethine imines; cycloaddition; diazabicyclohexanes; diaziridines; regioselectivity; Introduction Cyclic azomethine imines (AMIs) are very useful synthetic blocks for the preparation of diverse dinitrogenated heterocycles by 1,3

• -dipolar cycloadditions under thermal or catalytic conditions [1][2]. In general, cyclic azomethine imines are classified into two types, depending on their structure: N,N'-cyclic AMIs with both nitrogen atoms included in the cyclic system and C,N-cyclic AMIs having the C=N motif in the cycle (Scheme 1) [3

• ]. A wide range of pharmaceuticals, agrochemicals, and other biologically active compounds are prepared using different types of (3 + n) cycloadditions, mainly with alkenes and alkynes [3][4][5][6][7]. For example, N,N'-cyclic azomethine imines are precursors of biologically active bicyclic

[3 + 2]-Cycloaddition reaction of sydnones with alkynes

• Veronika Hladíková,
• Jiří Váňa and
• Jiří Hanusek

Beilstein J. Org. Chem. 2018, 14, 1317–1348, doi:10.3762/bjoc.14.113

• HOMO are possible – due to similar energy gaps – both electron-rich as well as electron-poor dipolarophiles/dipoles react more quickly than parent (unsubstituted) ones. Using semi-empirical quantum calculations (CNDO/2), Houk et al. [58] calculated average HOMO/LUMO energies for azomethine-imines

Enantioselective additions of copper acetylides to cyclic iminium and oxocarbenium ions

• Jixin Liu,
• Srimoyee Dasgupta and
• Mary P. Watson

Beilstein J. Org. Chem. 2015, 11, 2696–2706, doi:10.3762/bjoc.11.290

• with pyridines. In 2011, Maruoka and co-workers investigated the use of isoquinolinium ions protected as azomethine imines [30]. The use of a CuOAc/Ph-Pybox catalyst enables the addition of a wide variety of alkynes to form isoquinolines with tertiary stereocenters in high yields and ee’s (Scheme 8A

• azomethine imines. Su’s CDC of tetrahydroisoquinolines and alkynes under ball milling conditions. Ma’s A3-coupling. Li’s CDC reaction using photoredox catalysis. Liu’s CDC reaction of N-carbamoyltetrahydroisoquinolines. T+BF4– = 2,2,6,6-tetramethylpiperidine N-oxide tetrafluoroborate. Aponick’s alkynylation

Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

• synthetic value of this methodology (Scheme 34). 2.3 [3 + 2] Annulations of allenes with azomethine imines Using the chiral catalyst D4, a cyclic phosphine featuring a spiro-skeleton, Guo, Kwon, and co-workers achieved asymmetric [3 + 2] annulation of an allenoate with an azomethine imine (Scheme 35) [69

• ]. The reaction performed in dichloromethane at room temperature for 48 h afforded the product tetrahydropyrazolopyrazolone in 56% yield and 89% ee. Although only a single example was reported, their paper demonstrated that enantioselective [3 + 2] annulations of allenoates with azomethine imines could

Gold(I)-catalyzed enantioselective cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2013, 9, 2250–2264, doi:10.3762/bjoc.9.264

• methods that affords optically active cyclooctanes by means of a catalytic enantioselective process. Also recently, Chen and co-workers demonstrated that gold-activated allenamide species can participate in [3 + 2] cycloadditions with azomethine imines or nitrones under catalysis with Ph3PAuCl/AgOTf or

Dipolar addition to cyclic vinyl sulfones leading to dual conformation tricycles

• Steven S. Y. Wong,
• Michael G. Brant,
• Christopher Barr,
• Allen G. Oliver and
• Jeremy E. Wulff

Beilstein J. Org. Chem. 2013, 9, 1419–1425, doi:10.3762/bjoc.9.159

• Science Hall, Notre Dame, IN, 46556, USA 10.3762/bjoc.9.159 Abstract Dipolar addition of cyclic azomethine imines with cyclic vinyl sulfones gave rise to functionalized tricycles that exhibited fluxional behavior in solution at room temperature. The scope of the synthetic methodology was explored, and

• pathways are open to the reactants. The additional aromatic substituent in 7 (relative to 4) once again contributed to significant broadening in both the 1H and 13C NMR spectra. Conclusion Our results comprise the first syntheses of tricyclic sulfones by 1,3-dipolar cycloadditions of azomethine imines with

Photochemical and thermal intramolecular 1,3-dipolar cycloaddition reactions of new o-stilbene-methylene-3-sydnones and their synthesis

• Kristina Butković,
• Željko Marinić,
• Krešimir Molčanov,
• Biserka Kojić-Prodić and
• Marija Šindler-Kulyk

Beilstein J. Org. Chem. 2011, 7, 1663–1670, doi:10.3762/bjoc.7.196

• azomethine imines. Intramolecular 1,3-dipolar cycloadditions of sydnone derivatives have not been as thoroughly investigated, and so far only a few examples are known [18][19][20]. Photochemically induced intramolecular 1,3-dipolar cycloadditions have been studied on 3,4-disubstituted sydnone derivatives [18

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• with 1,3-dipoles [80], gold–carbenoids of type XXIII, generated from propargyl esters, can work as three-carbon synthons in cycloadditions with azomethine imines, also reported by Toste. An example is shown in Scheme 21 [81]. These (3 + 3) annulations take place through a stepwise mechanism related to

• that for the formation of azepines, consisting of a nucleophilic attack of the azomethine imines onto the intermediate alkenyl–gold carbenoid to afford an allyl–gold species XXIV’, which evolves to the final adduct through a stereoselective ring closure (Scheme 21). The scope of the method is rather

• azomethine imines with propargyl esters [81]. Gold(I)-catalyzed isomerization of 5-en-2-yn-1-yl acetates [83]. (3 + 2) and (2 + 2) cycloadditions of indole-3-acetates 41 [85][86]. Gold(I)-catalyzed (2 + 2) cycloaddition of allenenes [87]. Formal (3 + 2) cycloaddition of allenyl MOM ethers and alkenes [90

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

• -enaminone derivatives 161 and the cyclization of α-allenyl-β-enaminone intermediates has been developed by Saito and co-workers (Scheme 29) [75]. Toste’s group has reported a novel gold(III)-catalyzed [3 + 3]-annulation of azomethine imines 165 with propargyl esters 164. Substitution of the β-position of