Synthesis of bis-spirocyclic derivatives of 3-azabicyclo[3.1.0]hexane via cyclopropene cycloadditions to the stable azomethine ylide derived from Ruhemann's purple

• Alexander S. Filatov,
• Olesya V. Khoroshilova,
• Anna G. Larina,
• Vitali M. Boitsov and
• Alexander V. Stepakov

Beilstein J. Org. Chem. 2022, 18, 769–780, doi:10.3762/bjoc.18.77

• reductive amination/cyclization of enantiopure cis-cyclopropane dicarbonyls [26]. The strategy based on azomethine ylide cycloadditions to cyclopropenes enables ready access to a wide range of spiro-fused 3-azabicyclo[3.1.0]hexanes (Scheme 1a). Inspired by our recent achievements, we have focused on

• cycloadditions to stable azomethine ylide PRP (Scheme 1c). Results and Discussion The study commenced with testing the feasibility of the cycloaddition reaction between protonated Ruhemann's purple (PRP, 1) [28][29] and cyclopropene dipolarophiles 2. 1,2,3-Triphenylcycloprop-1-ene (TPC, 2a) [30] was chosen as a

• (MeOH) in 75% yield. Eventually, the constitution of 3a was unambiguously corroborated by NMR spectra. Given the results of previous studies [22][23] concerning cycloadditions of ninhydrin-derived azomethine ylides to cyclopropenes, it was suggested that the stable azomethine ylide 1 appears to react

Complementarity of solution and solid state mechanochemical reaction conditions demonstrated by 1,2-debromination of tricyclic imides

• Petar Štrbac and
• Davor Margetić

Beilstein J. Org. Chem. 2022, 18, 746–753, doi:10.3762/bjoc.18.75

• Zn/Ag couple in THF [19]. Linear exo,exo-product 25 was obtained exclusively in the reaction with DPIBF 24, which is in accordance to the stereospecificity of cycloadditions reported by Sasaki [25] where the linear adduct is greatly preferred over bent. An interesting feature of the 1H NMR spectrum

Structural basis for endoperoxide-forming oxygenases

• Takahiro Mori and
• Ikuro Abe

Beilstein J. Org. Chem. 2022, 18, 707–721, doi:10.3762/bjoc.18.71

• the synthesis of chemical reagents with an endoperoxide bridge have been reported [77][78]. The classical method for endoperoxide synthesis is through cycloadditions of dienes and alkenes, using singlet oxygen. Furthermore, cyclizations of hydroperoxides with pendant alkenes or alkynes have also been

Inductive heating and flow chemistry – a perfect synergy of emerging enabling technologies

• Conrad Kuhwald,
• Sibel Türkhan and
• Andreas Kirschning

Beilstein J. Org. Chem. 2022, 18, 688–706, doi:10.3762/bjoc.18.70

• 87%). Pericyclic reactions such as the Diels–Alder and hetero-Diels–Alder cycloadditions, the Alder-En reaction, as well as the decarboxylation of α-alkylated malonic acids, are also suitable for flow protocols in combination with inductive heating (Scheme 10, case A) [53]. The yields but especially

Site-selective reactions mediated by molecular containers

• Rui Wang and
• Yang Yu

Beilstein J. Org. Chem. 2022, 18, 309–324, doi:10.3762/bjoc.18.35

• Except for controlled cycloadditions, the site-selective reduction is also difficile to achieve. It mainly depends on the oxidative difference between the potential reactive sites and the careful picking of reductive reagents. Once the oxidative properties of these sites are similar to each other, it is

Iridium-catalyzed hydroacylation reactions of C1-substituted oxabenzonorbornadienes with salicylaldehyde: an experimental and computational study

• Angel Ho,
• Austin Pounder,
• Krish Valluru,
• Leanne D. Chen and
• William Tam

Beilstein J. Org. Chem. 2022, 18, 251–261, doi:10.3762/bjoc.18.30

• functionalization. Over the years, several interesting transformations have been investigated such as cycloadditions 4 [18][19][20][21][22][23], dimerizations 3 [24][25][26][27], isomerizations [28][29][30][31], among other reactions that have been reported [32][33][34][35][36][37][38]. The nucleophilic ring

Organocatalytic asymmetric nitroso aldol reaction of α-substituted malonamates

• Ekta Gupta,
• Narendra Kumar Vaishanv,
• Sandeep Kumar,
• Raja Krishnan Purshottam,
• Ruchir Kant and
• Kishor Mohanan

Beilstein J. Org. Chem. 2022, 18, 217–224, doi:10.3762/bjoc.18.25

• noteworthy and widely explored transformations of nitrosoarenes include nitroso ene reactions [9][10][11], Diels–Alder cycloadditions [12][13][14][15][16][17][18], and nitroso aldol reactions [19][20][21][22][23]. Among the various applications of nitrosoarenes, the asymmetric nitroso aldol reaction to

Selective sulfonylation and isonitrilation of para-quinone methides employing TosMIC as a source of sulfonyl group or isonitrile group

• Chuanhua Qu,
• Run Huang,
• Yong Li,
• Tong Liu,
• Yuan Chen and
• Guiting Song

Beilstein J. Org. Chem. 2021, 17, 2822–2831, doi:10.3762/bjoc.17.193

• combination of acidic α-carbon atoms, isocyano groups, and sulfonyl moieties [18]. In general, TosMIC undergoes base-mediated 1,3-dipolar cycloadditions with activated alkenes to provide pyrroles as products [18] (Scheme 1A). Recently, alternative functionalizations using TosMIC as a tosyl source of

Synthesis of new bile acid-fused tetrazoles using the Schmidt reaction

• Dušan Đ. Škorić,
• Olivera R. Klisurić,
• Dimitar S. Jakimov,
• Marija N. Sakač and
• János J. Csanádi

Beilstein J. Org. Chem. 2021, 17, 2611–2620, doi:10.3762/bjoc.17.174

• hazardous [26][27]. Some recent studies employ this reagent in the Schmidt synthesis of tetrazoles from ketones that are smaller in size and simpler than the steroidal ketones in this work [28][29]. For the synthesis of steroidal tetrazoles, most often 1,3-dipolar cycloadditions are being used. In this way

A study on selective transformation of norbornadiene into fluorinated cyclopentane-fused isoxazolines

• Zsanett Benke,
• Attila M. Remete and
• Loránd Kiss

Beilstein J. Org. Chem. 2021, 17, 2051–2066, doi:10.3762/bjoc.17.132

• multiple stereogenic centers. The synthesis involved selective cycloadditions, with subsequent ROM of the formed cycloalkene-fused isoxazoline scaffolds and selective CM by chemodifferentiation of the olefin bonds of the resulting alkenylated derivatives. Various experimental conditions were applied for

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

• catalyst with the corresponding acetylide by using LiOt-Bu. Further intermolecular [3 + 2]-cycloadditions of azide 67 with intermediate 70 affords a 5-copper(I)-substituted triazolide intermediate 71. The oxidative addition of 1-bromoalkyne 68 forms an alkyne–Cu(III)Br–triazole complex intermediate 72

A straightforward conversion of 1,4-quinones into polycyclic pyrazoles via [3 + 2]-cycloaddition with fluorinated nitrile imines

• Greta Utecht-Jarzyńska,
• Karolina Nagła,
• Grzegorz Mlostoń,
• Heinz Heimgartner,
• Marcin Palusiak and
• Marcin Jasiński

Beilstein J. Org. Chem. 2021, 17, 1509–1517, doi:10.3762/bjoc.17.108

• naphthoquinone-derived products and low-intensity bands in the visible region (≈400 nm) for the anthraquinone series. Keywords: [3 + 2]-cycloadditions; fluorinated compounds; fused pyrazoles; N-heterocycles; nitrile imines; 1,4-quinones; Introduction The 1,4-quinone scaffold belongs to the most important

• , and diverse transformations are known to create new C–C bonds and/or to extend the (poly)cyclic system. In this context, cycloadditions are of special importance, and Diels–Alder reactions have successfully been explored in conversions aimed at the construction of a new, six-membered ring [5]. However

• , [3 + 2]-cycloadditions leading to five-membered heterocycles are less often employed in spite of the high dipolarophilicity of the α,β-unsaturated diketone system [6][7][8][9]. Notably, in the already reported reactions of propargylic 1,3-dipoles, such as nitrile oxides or nitrile ylides, with 1,4

Synthesis of 1-indolyl-3,5,8-substituted γ-carbolines: one-pot solvent-free protocol and biological evaluation

• Premansh Dudhe,
• Mena Asha Krishnan,
• Kratika Yadav,
• Diptendu Roy,
• Krishnan Venkatasubbaiah,
• Biswarup Pathak and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2021, 17, 1453–1463, doi:10.3762/bjoc.17.101

• cycloisomerization/Pictet–Spengler cyclization of 2-(4-aminobut-1-yn-1-yl)aniline [16], the Ru and Rh-catalyzed [2 + 2 + 2] cycloadditions of yne-ynamides [17], and the Pd-catalyzed tandem coupling-cyclization [18] are significant works in the area (Scheme 1). However, the use of toxic and expensive metal catalysts

Fritsch–Buttenberg–Wiechell rearrangement of magnesium alkylidene carbenoids leading to the formation of alkynes

• Tsutomu Kimura,
• Koto Sekiguchi,
• Akane Ando and
• Aki Imafuji

Beilstein J. Org. Chem. 2021, 17, 1352–1359, doi:10.3762/bjoc.17.94

• synthesis [1]. Electrophilic additions of alkynes give functionalized compounds, and cycloadditions such as the Huisgen reaction afford cyclic compounds. Weakly acidic terminal alkynes can be deprotonated, and the resulting acetylides are used as carbon nucleophiles. Terminal alkynes are also used for the

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

• , 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

Synthesis of dibenzosuberenone-based novel polycyclic π-conjugated dihydropyridazines, pyridazines and pyrroles

• Ramazan Koçak and
• Arif Daştan

Beilstein J. Org. Chem. 2021, 17, 719–729, doi:10.3762/bjoc.17.61

• reaction conditions. Inverse electron-demand Diels–Alder reactions are cycloadditions between electron-rich dienophiles and electron-poor dienes. EDGs raise the electron density of dienes and, in parallel, raise the LUMOdiene–HOMOdienophile energy gap, and consequently the reactivity decreases. Although

[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

• 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

• open transannular bond (σ-homoaromatic structure) [79]. It was found that, as a rule, the [5,6]-open adducts formed initially can undergo rearrangement into [6,6]-closed isomers that are more thermodynamically stable. An alternative variant of [2 + 1] cycloadditions to the fullerene frame involves the

Synthesis of N-perfluoroalkyl-3,4-disubstituted pyrroles by rhodium-catalyzed transannulation of N-fluoroalkyl-1,2,3-triazoles with terminal alkynes

• Olga Bakhanovich,
• Viktor Khutorianskyi,
• Vladimir Motornov and
• Petr Beier

Beilstein J. Org. Chem. 2021, 17, 504–510, doi:10.3762/bjoc.17.44

• , conveniently prepared by [3 + 2] cycloadditions of terminal alkynes with sulfonyl azides, have been used as the precursors to N-sulfonylindoles by transition-metal-catalyzed transannulation reactions. In the presence of Rh(II) or Ni(0) catalysts the triazole ring-opening takes place and intermediate highly

Diels–Alder reaction of β-fluoro-β-nitrostyrenes with cyclic dienes

• Savva A. Ponomarev,
• Roman V. Larkovich,
• Alexander S. Aldoshin,
• Andrey A. Tabolin,
• Sema L. Ioffe,
• Jonathan Groß,
• Till Opatz and
• Valentine G. Nenajdenko

Beilstein J. Org. Chem. 2021, 17, 283–292, doi:10.3762/bjoc.17.27

• powerful tool for assembling a variety of fluorinated carbo- and heterocycles using either the diene [24][25][26][27][28][29][30] or the dienophile component [31][32][33][34][35][36][37][38][39] as fluorine-containing building blocks. The application of [4 + 2] cycloadditions for the preparation of

• [67] level of theory in combination with a Pople basis set and the IEFPCM [68] solvation model for o-xylene. Both functionals are already known in the literature for the investigation of cycloadditions [69][70][71][72]. For the computational details the reader is referred to Supporting Information

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

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

• -carbon quaternary centers in a single step and has been demonstrated in the synthesis of complex natural products. In this review, we present the development of all-carbon [3 + 2] cycloadditions and illustrate their application in natural product synthesis reported in the last decade covering 2011–2020

• timely and focused review of all-carbon [3 + 2] cycloadditions in natural product synthesis. In this review, we present the development of the all-carbon [3 + 2] cycloaddition and discuss its application in natural product synthesis reported from 2011–2020. We begin with describing the brief history of

• ] cycloadditions, which are usually under substrate-control. Remarkable innovation of the stereoselective palladium-catalyzed trimethylenemethane cycloaddition reported by Trost’s group, which makes use of catalytic amounts of palladium and chiral phosphine ligand 74, was applied successfully in the

A novel and robust heterogeneous Cu catalyst using modified lignosulfonate as support for the synthesis of nitrogen-containing heterocycles

• Bingbing Lai,
• Meng Ye,
• Ping Liu,
• Minghao Li,
• Rongxian Bai and
• Yanlong Gu

Beilstein J. Org. Chem. 2020, 16, 2888–2902, doi:10.3762/bjoc.16.238

• , ring-closing, metathesis, cycloadditions, radical reactions and microwave-assisted reactions [38][39][40]. In this work, we attempt to develop a greener, simpler, more efficient and recyclable system to synthesize arylpyridine derivatives. Initially, the reaction of acetophenone (5a) and 1,3

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

• -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

• AMIs can be generated in situ by thermal opening of any C–N bond of the diaziridine ring in 6-aryl-substituted 1,5-diazabicyclo[3.1.0]hexanes or 7-aryl-substituted 1,6-diazabicyclo[4.1.0]heptanes, respectively [16][17]. For the thermal generation conditions, the 1,3-dipolar cycloadditions of AMIs were

Dawn of a new era in industrial photochemistry: the scale-up of micro- and mesostructured photoreactors

• Emine Kayahan,
• Mathias Jacobs,
• Leen Braeken,
• Leen C.J. Thomassen,
• Simon Kuhn,
• Tom van Gerven and
• M. Enis Leblebici

Beilstein J. Org. Chem. 2020, 16, 2484–2504, doi:10.3762/bjoc.16.202

• metal cavity caused overheating. Therefore, a cooling jacket around the metal cavity was implemented in the design, along with a fan to blow air through the space between the lamp and the quartz photoreactor tubes. The design was called firefly reactor. Various [2 + 2] cycloadditions were performed in