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

• cyclopenta[e]indol-6-one 29k and cyclohepta[e]indol-6-one 29l from compounds 28k and 28l, respectively (Scheme 10C) [21]. In 2009, the Hansen group disclosed that treatment of 2-diazo-4-(4-indolyl)-3-oxobutanoate 30 with a catalytic amount of Rh2(OAc)4 resulted in the formation of the 4,5-fused tricyclic

• 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

• indole-derived phenylenediamines. Indole C5 regioselective intramolecular FC acylation of 4-substituted indoles. Catalyst-dependent regioselectivity switching in the cyclization of ethyl 2-diazo-4-(4-indolyl)-3-oxobutanoate. Indole C5 regioselective cyclization of α-carbonyl sulfoxonium ylides. Indole 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

• Yelong Lei Jiaxi Xu State Key Laboratory of Chemical Resource Engineering, Department of Organic Chemistry, College of Chemistry, Beijing University of Chemical Technology, Beijing 100029, People’s Republic of China 10.3762/bjoc.18.6 Abstract Alkyl 2-diazo-3-oxoalkanoates generate

• -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

• 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

Synthesis of new pyrazolo[1,2,3]triazines by cyclative cleavage of pyrazolyltriazenes

• Nicolai Wippert,
• Martin Nieger,
• Claudine Herlan,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2021, 17, 2773–2780, doi:10.3762/bjoc.17.187

• of the intermediate diazo compounds under acidic conditions [22] (Scheme 1). The structurally related 3,7-dihydro-4H-pyrazolo[3,4-d][1,2,3]triazin-4-ones 3 (Figure 1) which are substituted in position N-7 can be obtained in the same manner as described in Scheme 1, if the substitution position R1 in

α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

• Scott Benz and
• Andrew S. Murkin

Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172

• biologically. Prekinamycin (76) and isoprekinamycin (77) are diazo compounds isolated from Streptomyces murayamensis that differ in their ring system, with the former containing a fused 6-6-5-6 skeleton and the latter containing a 6-5-6-6 skeleton. Due to their similarity and common source, it had been

• hypothesized by several groups that one could be the biological precursor of the other by means of a reversible hydration–rearrangement–dehydration sequence (Figure 16a) [24][25][26]. The presence of the diazo group in intermediates 78 and 79 is noteworthy in that this functional group has not yet been

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

• takes place to form intermediate 22, which subsequently converts to diazo-functionalized intermediate 23. Finally, the intramolecular annulation of intermediate 23 gives corresponding fully decorated 1,2,3-triazole 19 (Scheme 9) [42]. A domino coupling synthesis of fully decorated 1,2,3-triazole

• -diazo-ß-ketosulfones 37, I2, and K2CO3 in EtOH. The scope and limitations of the reaction were assessed using alkyl aldehydes, (hetero)aryl aldehydes, amines, and diazosulfones. Reactions of aryl aldehydes containing a range of different functional groups gave products 38 in very good yield. Because of

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

Synthesis of β-triazolylenones via metal-free desulfonylative alkylation of N-tosyl-1,2,3-triazoles

• Soumyaranjan Pati,
• Renata G. Almeida,
• Eufrânio N. da Silva Júnior and
• Irishi N. N. Namboothiri

Beilstein J. Org. Chem. 2021, 17, 762–770, doi:10.3762/bjoc.17.66

• many bioactive heterocycles [36]. These are also important precursors of diazo adducts which are used in insertion, cyclopropanation, and various rearrangements to construct various cyclic as well as acyclic moieties under metal-catalysed conditions [37][38]. On the contrary, under basic conditions

• , these diazo compounds undergo [3 + 2] cycloadditions with suitable substrates to render various nitrogen-rich heterocycles [39]. In addition to their synthetic importance, these are frequently encountered as ligands in many metal complexes [40][41][42][43]. Our group have also employed 1,3-dicarbonyl

[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

• promising. They are synthesized in two main reactions: nucleophilic cyclopropanation according to the Bingel method and thermal addition of diazo compounds. This present review summarizes the material on the synthesis of monofunctionalized methanofullerenes – analogues of [60]PCBM – based on various diazo

• ]PCBM; diazo compounds; mechanisms and optimal conditions of cyclopropanation; methanofullerenes C60; Introduction Taking into consideration that all life on Earth is of organic origin. with carbon as its basic element (20% by weight of every living organism, and the fourth most abundant element in the

• discuss the primary functionalization of the fullerene core with diazo compounds to synthesize solely monosubstituted carbochain products, covers the main achievements of organic chemistry over the past 20 years in the field of [2 + 1] cycloadditions to fullerene. Review [2 + 1] Cycloaddition to C60 to

Synthetic strategies of phosphonodepsipeptides

• Jiaxi Xu

Beilstein J. Org. Chem. 2021, 17, 461–484, doi:10.3762/bjoc.17.41

• insertion reactions. The reaction of the N-protected amino acids 209 and 210 with diethyl 1-diazo-2,2,2-trifluoroethylphosphonate (211) gave rise to the trifluoromethyl-containing phosphonodepsipeptides 212 and 213 with C-1-hydroxyalkylphosphonic acids in good yields under the catalysis of dirhodium

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

• formation of CF3-containing alkylcarbenium ions from diazonium salts: In 1967, Mohrig et al. successfully observed the first aliphatic diazonium ion 218a by protonation of the corresponding diazo precursor [142] 217a in a superacid by in situ NMR spectroscopy (Scheme 54) [143]. The remarkable characteristic

Selective synthesis of α-organylthio esters and α-organylthio ketones from β-keto esters and sodium S-organyl sulfurothioates under basic conditions

• Jean C. Kazmierczak,
• Roberta Cargnelutti,
• Thiago Barcellos,
• Claudio C. Silveira and
• Ricardo F. Schumacher

Beilstein J. Org. Chem. 2021, 17, 234–244, doi:10.3762/bjoc.17.24

• synthesis and medicinal chemistry. In the last years, different methods have been developed to prepare these classes of molecules, which includes the reaction of alkynes [39][40][41][42][43] as well as α-halogenated [44][45] and α-diazo carbonyl compounds [46][47][48][49] with thiols, diorganyl disulfides

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

• trimethylenemethane diyl [3 + 2] cycloaddition of 40 led to the formation of angular fused triquinane 41 in 98% yield. The authors suggested that an intramolecular cycloaddition of the diazo group and allene 38 produces tetrahydrocyclopentapyrazole 39. Extrusion of nitrogen from the newly formed 39 produces diyl 40

• 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

Regioselective synthesis of heterocyclic N-sulfonyl amidines from heteroaromatic thioamides and sulfonyl azides

• Vladimir Ilkin,
• Vera Berseneva,
• Tetyana Beryozkina,
• Tatiana Glukhareva,
• Lidia Dianova,
• Wim Dehaen,
• Eugenia Seliverstova and
• Vasiliy Bakulev

Beilstein J. Org. Chem. 2020, 16, 2937–2947, doi:10.3762/bjoc.16.243

• reactions of 2-diazomalonates with aliphatic amines [40][52]. The first approach leads to a mixture of two regioisomers and the second method involves the use of explosive diazo compounds. Therefore, such compounds are better prepared by a recently found method in our laboratory which includes the reaction

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

• formation started in 2016 with the report from Gryko’s group on the photoredox α-alkylation of aldehydes with diazo compounds using 1 mol % of TPP or ZnTPP as photocatalyst [10] (Scheme 1), thus obtaining functionalized aldehydes in 47–90% yields. These results are similar to those previously reported by

• 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

• excited state potentials, including porphyrin derivatives. Adapted from [10][12][22]. Electronic configurations of the species of oxygen. Adapted from [66]. Photoredox alkylation of aldehydes with diazo acetates using porphyrins and a Ru complex. aUsing a loading of 0.1 mol % for ZnTPP. Proposed mechanism

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

• ; 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

• ), and PhSO2CF2CHN2 (3, Ps-DFA). Initial screenings were focused on the evaluation of various chiral phosphoric acids that have proven effective in similar aza-Darzens reactions of diazo esters and trifluorodiazoethane [36][37][38][39]. Unfortunately, these endeavors resulted in either no conversion or

• -methoxyaniline (2a, 40.6 mg, 0.33 mmol), 2-boronobenzoic acid (COOH-BA, 3.98 mg, 0.024 mmol), anhydrous Na2SO4 (200 mg) and toluene (1 mL) at room temperature under an argon atmosphere. After reacting for 30 minutes at room temperature, ((2-diazo-1,1-difluoroethyl)sulfonyl)benzene (Ps-DFA 3, 104.5 mg, 77.4 uL

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

• Maria Eremeyeva Daniil Zhukovsky Dmitry Dar'in Mikhail Krasavin Laboratory of Chemical Pharmacology, Institute of Chemistry, Saint Petersburg State University, 26 Universitetskii prospect, Peterhof 198504, Russian Federation 10.3762/bjoc.16.55 Abstract N-Alkyl α-diazo-γ-butyrolactams, previously

• , the reactions tended to yield enamine adducts. Keywords: in situ reactions; N-alkyl 2-pyrrolidones; RhII-catalyzed insertion reactions; stability of diazo compounds; Introduction Recently, we described the first synthesis and subsequent transformations of a rare type of cyclic α-diazocarbonyl

• compounds, namely, α-diazo-γ-butyrolactams [1]. In particular, N-aryl-α-diazo-γ-butyrolactams 1 were efficiently transformed into pyrrolinones 2 upon the treatment with AgOTf (1 mol %) and into α-alkoxy derivatives 3 via Rh2(OAc)4-catalyzed O–H insertion reactions with various alcohols. In contrast, N-alkyl

Copper-promoted/copper-catalyzed trifluoromethylselenolation reactions

• Clément Ghiazza and
• Anis Tlili

Beilstein J. Org. Chem. 2020, 16, 305–316, doi:10.3762/bjoc.16.30

• moieties. One year later, the group of Goossen demonstrated the direct conversion of diazo compounds into trifluoromethylselenolated products using a catalytic amount of copper(I) thiocyanate (Scheme 11) [28][29]. The reaction proceeded under mild conditions, and the desired products were usually obtained

AgNTf₂-catalyzed formal [3 + 2] cycloaddition of ynamides with unprotected isoxazol-5-amines: efficient access to functionalized 5-amino-1H-pyrrole-3-carboxamide derivatives

• Ziping Cao,
• Jiekun Zhu,
• Li Liu,
• Yuanling Pang,
• Laijin Tian,
• Xuejun Sun and
• Xin Meng

Beilstein J. Org. Chem. 2019, 15, 2623–2630, doi:10.3762/bjoc.15.255

• attacking of nucleophilic partners, followed by a protodemetalation step to form the alkene motif (Scheme 1, path a) [9][10][11]. However, the formation of a silver carbene intermediate, which could be generated usually from relevant diazo precursors [12][13][14], appears to be an unusual event in silver

• species could be also involved mechanistically in the Ag-mediated reaction of enynals with conjugated dienes [18] and the homodimerization of enynals [19][20]. So, the studies on the reactions of alkynes involving the generation of silver carbene species from non-diazo precursors are of great value for

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

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

• decomposition of diazo compounds, are particularly versatile intermediates in organic synthesis, as they partake in cyclopropanation and C–H insertion reactions with high levels of selectivity [2]. This transition-metal-catalyzed carbene transfer has emerged as a mild and attractive route to indole

• 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

The cyclopropylcarbinyl route to γ-silyl carbocations

• Xavier Creary

Beilstein J. Org. Chem. 2019, 15, 1769–1780, doi:10.3762/bjoc.15.170

• ? Answers to these questions were sought. Results and Discussion Phenyl-substituted systems The first compounds to be examined were the mesylates 19 and 20. These substrates were prepared as shown in Scheme 4. Irradiation of ethyl 2-diazo-2-phenylacetate (15) in vinyltrimethylsilane as solvent gave an

Formation of an unexpected 3,3-diphenyl-3H-indazole through a facile intramolecular [2 + 3] cycloaddition of the diazo intermediate

• Andrew T. King,
• Hugh G. Hiscocks,
• Lidia Matesic,
• Mohan Bhadbhade,
• Roger Bishop and
• Alison T. Ung

Beilstein J. Org. Chem. 2019, 15, 1347–1354, doi:10.3762/bjoc.15.134

• a = 9.2107 (4), b = 10.0413 (5), c = 14.4363 (6) Å, α = 78.183 (2), β = 87.625 (2), γ = 71.975 (2)°. The formation of 8 proceeded through a facile intramolecular [2 + 3] cycloaddition of the diazo intermediate 9. The molecules of 8 are organised by edge–face Ar–H···π, face–face π···π, and bifurcated

• OCH2–H···N interactions. In addition to these, there are Ar–H···H–Ar close contacts, (edge–edge and surrounding inversion centres) arranged as infinite tapes along the a direction. Keywords: Ar-H...H-Ar contact; [2 + 3] cycloaddition; diazo; 3H-indazole; X-ray structure; Introduction The use of

• -related counterpart: C6C···C5C = 3.50 Å (Figure 4b). The C4 methoxy and the heterocyclic diazo functionality of 8 are linked through an interesting arrangement along the b axis that can be described either as a OCH2–H···π (N=N) or as a bifurcated N···H(CH2O)···N interaction. This motif is close to

Alkylation of lithiated dimethyl tartrate acetonide with unactivated alkyl halides and application to an asymmetric synthesis of the 2,8-dioxabicyclo[3.2.1]octane core of squalestatins/zaragozic acids

• Herman O. Sintim,
• Hamad H. Al Mamari,
• Hasanain A. A. Almohseni,
• Younes Fegheh-Hassanpour and
• David M. Hodgson

Beilstein J. Org. Chem. 2019, 15, 1194–1202, doi:10.3762/bjoc.15.116

• acetonide removal, this would give an α-ketoester 10. The latter should in principle be a progenitor to the desired α-diazo ester 3, following condensation with tosylhydrazide, then Bamford–Stevens-type base-induced sulfinate elimination [20] and oxidation of the secondary silyl ether. Results and

• % yield [21], gave α-diazo ester 13 in 76% yield following reaction with NaOMe. Furthermore, our earlier racemic model study had established that deprotection and oxidation of a secondary silyl ether in the presence of α-diazo ester functionality was feasible, which constitutes precedent for the

• ); therefore, 20 and the derived tertiary TBS ether 21 were carried on directly to form hydrazone 22 (51% yield over 3 steps from hydroxy acetonide 19a). Unlike with hydrazone 12 (Scheme 3), application of NaOMe was not conducive to effective diazo formation from hydrazone 22, giving a mixture of unidentified

Diastereo- and enantioselective preparation of cyclopropanol derivatives

• Marwan Simaan and
• Ilan Marek

Beilstein J. Org. Chem. 2019, 15, 752–760, doi:10.3762/bjoc.15.71

• 3 were easily prepared through the well-known RhII-catalyzed decomposition of diazo esters in the presence of alkynes to give cyclopropenyl esters 1. Reduction of 1 using DIBAL-H afforded cyclopropenyl alcohols 2 and subsequent protection of the primary alcohols gave 3 in good yields (Scheme 3