Synthesis, structure and π-expansion of tris(4,5-dehydro-2,3:6,7-dibenzotropone)

• Yongming Xiong,
• Xue Lin Ma,
• Shilong Su and
• Qian Miao

Beilstein J. Org. Chem. 2025, 21, 1–7, doi:10.3762/bjoc.21.1

• the carbonyl groups in 1, it was treated with three equivalents Lawesson's reagent, affording dithioketone 8a in a 40% yield together with trithioketone 8b in a yield of 10%. To expand the π-skeleton of 1, compound 8a was subjected to the Barton–Kellogg reaction with diazo compound 9, which was

Synthesis of 2H-azirine-2,2-dicarboxylic acids and their derivatives

• Anastasiya V. Agafonova,
• Mikhail S. Novikov and
• Alexander F. Khlebnikov

Beilstein J. Org. Chem. 2024, 20, 3191–3197, doi:10.3762/bjoc.20.264

• reaction of more branched alcohols failed. Such esters could be prepared from the dicarboxylic acids using traditional activation or OH-insertion reaction of carbenes formed by irradiation of the appropriate diazo compound. Approaches to 2H-azirine-2,2-dicarboxylic acid derivatives. Synthesis of 2H-azirine

Advances in radical peroxidation with hydroperoxides

• Oleg V. Bityukov,
• Pavel Yu. Serdyuchenko,
• Andrey S. Kirillov,
• Gennady I. Nikishin,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2024, 20, 2959–3006, doi:10.3762/bjoc.20.249

• formation of tert-butylperoxy A and tert-butoxy B radicals is assumed to be the result of the Cu(I)/Cu(II) catalytic cycle. Diazo compound 114 reacts with Cu(I) giving complex C, which is reduced with isopropanol to intermediate D. The oxidative addition of TBHP to complex D gives intermediate E, which is

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

• 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

Harnessing the versatility of hydrazones through electrosynthetic oxidative transformations

• Aurélie Claraz

Beilstein J. Org. Chem. 2024, 20, 1988–2004, doi:10.3762/bjoc.20.175

• access to diazo compounds as either synthetic intermediates or products. A special attention is paid to the reaction mechanism with the aim to encourage further development in this field. Keywords: C–H functionalization; diazo compound; electrosynthesis; hydrazone; nitrogen-containing heterocycle

• of the iodonium species [(CH3CN)2I+], which would react with the hydrazone to furnish the protonated diazo compound 143 via the N-iodo hydrazone intermediate 142. Further acetate anion-assisted deprotonation ultimately led to the desired diazo compounds 141 (Scheme 30) [80]. A nice application of

• photoelectrochemical transformation began with the anodic oxidation of the hydrazone 146 to the corresponding diazo compound 149, akin to Lam and Ollevier’s work. Subsequent (3 + 2)-cycloaddition with the olefin partner 147 formed cyclic diazene 150. Meanwhile, anodic oxidation of TAC+ generated photosensitive TAC2

Access to 2-oxoazetidine-3-carboxylic acid derivatives via thermal microwave-assisted Wolff rearrangement of 3-diazotetramic acids in the presence of nucleophiles

• Ivan Lyutin,
• Vasilisa Krivovicheva,
• Grigory Kantin and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2024, 20, 1894–1899, doi:10.3762/bjoc.20.164

• tested in a previous study [3]. The reaction requires rather severe heating under microwave irradiation (200 °C, chlorobenzene, sealed vial), ensuring complete conversion of the diazo compound in a rather short time. Initial experiments using p-anisidine as a nucleophile showed that the target β-lactam

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

• diazo precursor. To achieve this, cholesterol was first esterificated using 2-(4-methoxyphenyl)acetic acid and DCC. The resulting arylacetic ester 12 was then reacted with 4-acetamidobenzenesulfonyl azide (p-ABSA) and DBU in anhydrous acetonitrile to yield the diazo compound 13 in 22% yield. The carbene

Palladium-catalyzed three-component radical-polar crossover carboamination of 1,3-dienes or allenes with diazo esters and amines

• Geng-Xin Liu,
• Xiao-Ting Jie,
• Ge-Jun Niu,
• Li-Sheng Yang,
• Xing-Lin Li,
• Jian Luo and
• Wen-Hao Hu

Beilstein J. Org. Chem. 2024, 20, 661–671, doi:10.3762/bjoc.20.59

• -light-mediated palladium-catalyzed three-component radical-polar crossover carboamination of 1,3-dienes or allenes with diazo esters and amines, affording unsaturated γ- and ε-amino acid derivatives with diverse structures. In this methodology, the diazo compound readily transforms into a hybrid α-ester

• a highly emerging area of research and exhibit complementary reactivity to those well-developed carbene-mediated MCRs [30][31][32][33][34][35][36][37][38][39][40][41][42]. In the radical-mediated difunctionalization of alkenes, the carbon-centered radical species from a diazo compound can add to

• diverse alkenes followed by a diradical coupling or radical addition process to achieve the difunctionalization (Scheme 1b, middle) [32][33][34][35][36][37]. However, to the best of our knowledge, the methodology involving the addition of a carbon radical from a diazo compound onto the double bond of an

Entry to new spiroheterocycles via tandem Rh(II)-catalyzed O–H insertion/base-promoted cyclization involving diazoarylidene succinimides

• Alexander Yanovich,
• Anastasia Vepreva,
• Ksenia Malkova,
• Grigory Kantin and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2024, 20, 561–569, doi:10.3762/bjoc.20.48

• earlier and the synthetic methodology investigated in this work. An initial example on Rh(II)-catalyzed O–H insertion/base-promoted cyclization involving diazo compound 1a. Tandem Rh2(esp)2-catalyzed O–H insertion/base-promoted cyclization involving DAS 1 and various propiolic acids; PMP = 4-methoxyphenyl

Cycloaddition reactions of heterocyclic azides with 2-cyanoacetamidines as a new route to C,N-diheteroarylcarbamidines

• Pavel S. Silaichev,
• Tetyana V. Beryozkina,
• Vsevolod V. Melekhin,
• Valeriy O. Filimonov,
• Andrey N. Maslivets,
• Vladimir G. Ilkin,
• Wim Dehaen and
• Vasiliy A. Bakulev

Beilstein J. Org. Chem. 2024, 20, 17–24, doi:10.3762/bjoc.20.3

• opening of triazole 6 to form diazo compound anti-7, followed by rotation around the C‒C bond of the amidine group to furnish rotamer syn-7 which then undergoes 1,5-dipolar cyclization to products 3. The second path involves a Dimroth-type cyclization to form products 3′, which however, were not

N-Boc-α-diazo glutarimide as efficient reagent for assembling N-heterocycle-glutarimide diads via Rh(II)-catalyzed N–H insertion reaction

• Grigory Kantin,
• Pavel Golubev,
• Alexander Sapegin,
• Alexander Bunev and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2023, 19, 1841–1848, doi:10.3762/bjoc.19.136

• )-catalyzed N–H insertion reactions involving NH-heterocycles. The proposed method enables the synthesis of multigram quantities of diazo compound 5 rapidly. Furthermore, it can be stored up to several weeks in the refrigerator (5 °C) without any observable alterations. A diverse array of NH-heterocycles with

• tetrazoles, had not been previously utilized in the CRBN ligands design. Catalytic decomposition reactions of diazo compound 5 with NH-heterocycles were conducted in a dry DCM solution using dirhodium espinoate (Rh2(esp)2, 0.06–0.18 mol %). The Rh2(esp)2 catalyst was selected for its excellent versatility

Exploring the role of halogen bonding in iodonium ylides: insights into unexpected reactivity and reaction control

• Carlee A. Montgomery and
• Graham K. Murphy

Beilstein J. Org. Chem. 2023, 19, 1171–1190, doi:10.3762/bjoc.19.86

• series of ylide precursors and found that when diazo compound 69 was reacted with 67 (with or without a transition-metal catalyst), no reaction occurred. Conversely, iodonium ylides 31, 70 and 71 all reacted with 67 to produce 68 in 28–81% yield. A significant improvement was realized when an ortho-ether

Pyridine C(sp²)–H bond functionalization under transition-metal and rare earth metal catalysis

• Haritha Sindhe,
• Malladi Mounika Reddy,
• Karthikeyan Rajkumar,
• Akshay Kamble,
• Amardeep Singh,
• Anand Kumar and
• Satyasheel Sharma

Beilstein J. Org. Chem. 2023, 19, 820–863, doi:10.3762/bjoc.19.62

• and the base the initial direct C–H activation of the ylide 12 gives the copper pyridinium ylide 15. The latter reacts with the diazo compound formed through reaction of hydrazone 13 with the base to give the copper–carbene species 16. Then, the intermediate 16 undergoes a Cu–carbene migratory

Access to cyclopropanes with geminal trifluoromethyl and difluoromethylphosphonate groups

• Ita Hajdin,
• Romana Pajkert,
• Mira Keßler,
• Jianlin Han,
• Haibo Mei and
• Gerd-Volker Röschenthaler

Beilstein J. Org. Chem. 2023, 19, 541–549, doi:10.3762/bjoc.19.39

• % yield (Table 1, entry 6). In addition, in a catalyst-free reaction under UV irradiation, no reaction occurred and the starting diazo compound 5 was recovered (Table 1, entry 7). Having identified the optimal catalyst and conditions, we then examined the scope of the cyclopropanation reaction by reacting

• olefins with different aliphatic chains. The total conversion of the diazo compound 5 was achieved after 2.5–3.5 hours of heating and the corresponding cyclopropanes 7a–g were obtained in moderate to good yield (28–53%). The highest yield (53%) as well as the best diastereoselectivity were recorded for

• chromatography were unsuccessful. In addition, alkenes such as allylpentafluorobenzene, diethyl allylmalonate, allylbenzene and ethyl acrylate did not react with 5. Instead, the diazo compound 5 decomposed immediately under the reaction conditions described in Scheme 4. To better understand the mechanism and to

Vicinal ketoesters – key intermediates in the total synthesis of natural products

• Marc Paul Beller and
• Ulrich Koert

Beilstein J. Org. Chem. 2022, 18, 1236–1248, doi:10.3762/bjoc.18.129

• mesoxalic ester amide 102 in a Friedel–Crafts reaction followed by a spontaneous lactamization to give (rac)-cladoniamide G (103). The mesoxalic ester amide 102 was synthesized from malonyl chloride 104 through amidation and Regitz diazotransfer, yielding diazo compound 105. Subsequent oxidation and

Regioselectivity of the S_EAr-based cyclizations and S_EAr-terminated annulations of 3,5-unsubstituted, 4-substituted indoles

• Jonali Das and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2022, 18, 293–302, doi:10.3762/bjoc.18.33

• catalysis diazo compound 30 delivered 3,4-fused tricyclic indole derivative 32 which underwent spontaneous rearrangement to thermodynamically more stable naphthalene derivative 33 upon standing for a few hours. To the best of our knowledge, this is the only report of catalyst-controlled C3 versus C5

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

• -2-yl)alkanamides and 1-(oxazolin-2-yl)alkylphosphonates. Keywords: aziridine; diazooxoester; diazo compound; ketene; oxazoline; ring expansion; Introduction Oxazoline derivatives are an important class of nitrogen and oxygen-containing five-membered unsaturated heterocycles [1] and widely exist in

• [23], 1c,d [24], 1e,g [25], 1f [26], 1h [27] and 1i [28]. Aziridines 2 were prepared according to our previous method [21] and their analytic data are identical to previously reported ones 2a–f [21] and 2g [29]. General procedure for the synthesis of ethyl 2-(oxazol-2-yl)alkanoates 3 Diazo compound 1

[2 + 1] Cycloaddition reactions of fullerene C₆₀ based on diazo compounds

• Yuliya N. Biglova

Beilstein J. Org. Chem. 2021, 17, 630–670, doi:10.3762/bjoc.17.55

• C60 or b) possible formation of both isomers as a result of 1,3-dipolar cycloaddition of the diazo compound to the fullerene, followed by elimination of molecular nitrogen from the pyrazoline intermediate. Second, the rearrangement of [5,6]-open isomers into thermodynamically more stable [6,6]-closed

• methanofullerene in the reaction mixture after the loss of H2 depends on the diazo compound used for the cycloaddition. According to 13C NMR data, the [6,5]-bridged compound 5 has an open transannular bond, while the [6,6]-bridged compound 6 has a closed trans-ring bond. A synthetically interesting building block

• with tosylhydrazone The first publication on the synthesis of methanofullerenes via tosyl derivatives appeared in 1993 [83]. According to the original source, C60 cyclopropanation is assumed to involve a diazo compound preliminarily synthesized from an aldehyde- or ketone-based tosylhydrazone. The

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• triquinane (±)-hirsutene (14) [24] (Scheme 1D). In 2011, the same research group used allenyl diazo compound 38, which was generated from the reaction between aldehyde 37 and p-toluenesulfonehydrazide in the presence of sodium hydride upon heating, to produce diyl 40 [29] (Scheme 2A). The intramolecular

• 2014 and 2017, respectively (Scheme 2B and Scheme 2C). The synthesis of (−)-crinipellin A (15) began with the treatment of hydrazone 42 with sodium hydride under reflux to produce the tetraquinane 46 in 87% yield [30] (Scheme 2B). The authors suggested that the diazo compound 43 formed undergoes an

• ] cycloaddition produces tricycle 36 in the preparation of (±)-hirsutene (14) [24]. (A) An intramolecular trimethylenemethane diyl [3 + 2] cycloaddition with allenyl diazo compound 38 as a key intermediate to give angular-fused triquinane 41 [29]. (B) Synthesis of (−)-crinipellin A (15) [30]. (C) Synthesis of

Photocatalytic trifluoromethoxylation of arenes and heteroarenes in continuous-flow

• Alexander V. Nyuchev,
• Ting Wan,
• Borja Cendón,
• Carlo Sambiagio,
• Job J. C. Struijs,
• Michelle Ho,
• Moisés Gulías,
• Ying Wang and
• Timothy Noël

Beilstein J. Org. Chem. 2020, 16, 1305–1312, doi:10.3762/bjoc.16.111

• recently reported [8][9][11], for example the trifluoromethylation of hydroxyaryls [12][13][14], and the direct introduction of the -OCF3 moiety into an organometallic species [15], a diazo compound [16][17], or an unfunctionalized C–H bond (Scheme 1B). The latter method is particularly interesting

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• this transformation involves the formation of an aryl radical by SET between the diazo compound and the porphyrin in its excited state (Scheme 3). The authors demonstrated that meso-arylated porphyrins can efficiently act by an oxidative quenching. However, issues about why an electron-poor porphyrin

Preparation and in situ use of unstable N-alkyl α-diazo-γ-butyrolactams in Rh^II-catalyzed X–H insertion reactions

• Maria Eremeyeva,
• Daniil Zhukovsky,
• Dmitry Dar’in and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2020, 16, 607–610, doi:10.3762/bjoc.16.55

• immediate addition of the X–H insertion partner and a RhII catalyst to the solution of the diazo compound. The reactions are rapid, albeit moderately yielding. Despite the latter drawback, the range of 1,3-disubstituted 2-pyrrolidones attainable via the intermediate formation of α-diazo-γ-butyrolactams was

Cyclopropanation–ring expansion of 3-chloroindoles with α-halodiazoacetates: novel synthesis of 4-quinolone-3-carboxylic acid and norfloxacin

• Sara Peeters,
• Linn Neerbye Berntsen,
• Pål Rongved and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2019, 15, 2156–2160, doi:10.3762/bjoc.15.212

• functionalization [3][4][5][6]. The metal carbene reactions with indoles have been studied for the three types of carbenoids: acceptor–acceptor [7][8][9], mono-acceptor [10] and donor–acceptor carbenoids [11][12][13][14]. Depending on the metal and the diazo compound, the chemo- and regioselectivity in the metal

Reusable and highly enantioselective water-soluble Ru(II)-Amm-Pheox catalyst for intramolecular cyclopropanation of diazo compounds

• Hamada S. A. Mandour,
• Yoko Nakagawa,
• Masaya Tone,
• Hayato Inoue,
• Nansalmaa Otog,
• Ikuhide Fujisawa,
• Soda Chanthamath and
• Seiji Iwasa

Beilstein J. Org. Chem. 2019, 15, 357–363, doi:10.3762/bjoc.15.31

• cyclopropanation using various diazo compounds with Ru(II)-Amm-Pheox Several diazoacetates and diazoacetamides were tested for asymmetric intramolecular cyclopropanation reactions using Ru(II)-Amm-Pheox catalyst (cat. 2) in H2O/ether biphasic medium as shown in Table 1. A diazo compound derived from allyl

• diazoacetate could be cyclopropanated affording the corresponding lactone with low yield and good enantioselectivity (Table 1, entry 1). In case of the diazo compound derived from cinnamyl diazoacetate the corresponding lactone was obtained in high yield with high enantioselectivity (Table 1, entry 2). A

• amide derivatives bearing electron-donating or electron-withdrawing groups at the ortho, meta, or para positions could be converted to the corresponding bicyclic products in excellent yields (up to 99%) and enantioselectivities (up to 98% ee, Scheme 1, 2g−m). A diazo compound with two chlorine