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

• toluene [173]. N-Vinylimidazole, an alkene with a leaving group, was used to synthesize the 3-substituted pyrazoles 169 because, unlike acetylene, it is not gaseous and, therefore, easier to handle. Instead of vinylimidazole, vinyl azides 170 can also be used as alkyne surrogates. After the 1,3-dipolar

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• utility of their reaction, the authors studied the one-pot conversion of the vinyl azides to 2H-azirines 161. The carboazidation reaction for the aryl alkynes was completed in a comparable amount of time. A myriad of different functionalized π-systems was tolerated by the reaction, demonstrating its

Visible-light-mediated copper photocatalysis for organic syntheses

• Yajing Zhang,
• Qian Wang,
• Zongsheng Yan,
• Donglai Ma and
• Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

• [Cu(dap)2Cl] and visible light are necessary for this transformation. In 2013, Ollivier and co-workers [45] successfully applied the same strategy to the allylation of diphenyliodonium 2. In 2017, Liu’s group [46] reported the copper salt-catalyzed cyclization of vinyl azides 3 with ammonium

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

• products. The tolylvinyl azide substituted with methyl at the ortho position afforded a lower yield of the desired product. The vinyl azides containing 2-naphthyl, β-phenyl, and 1-((2-azidoallyl)oxy)-4-nitrobenzenevinyl azides formed the corresponding products in high yield as well. Moreover, the alkyl

• enone 46 reacted with aryl and vinyl azides to afford a moderate to high yield of the triazole products (Scheme 16) [46]. A simple one-pot two-stage strategy for the synthesis of disubstituted 4-chloro-, 4-bromo-, and 4-iodo-1,2,3-triazoles 50 from the reaction of the corresponding nonactivated alkynes

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

A sustainable strategy for the straightforward preparation of 2H-azirines and highly functionalized NH-aziridines from vinyl azides using a single solvent flow-batch approach

• Michael Andresini,
• Leonardo Degannaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2021, 17, 203–209, doi:10.3762/bjoc.17.20

• preparation of 2H-azirines and their stereoselective transformation into highly functionalized NH-aziridines, starting from vinyl azides and organolithium compounds. The protocol has been developed using cyclopentyl methyl ether (CPME) as an environmentally benign solvent, resulting into a sustainable, safe

• of vinyl azides, or by other strategies involving oximes, imines and oxazoles [24]. One appealing strategy for the preparation of 2H-azirines involves the use of readily available vinyl azides [25][26][27][28][29][30]. However, the batch cyclization of vinyl azides into the corresponding 2H-azirines

• resulted in safer procedures for the preparation of 2H-azirines, offering valuable alternatives for production purposes. In 2013, Kirschning harnessed the photoinduced electrocyclization of vinyl azides in a microfluidic photoreactor yielding 2H-azirines as precursors of 1,3-dipolarophiles (Scheme 1a) [27

Photocatalyzed syntheses of phenanthrenes and their aza-analogues. A review

• Alessandra Del Tito,
• Havall Othman Abdulla,
• Davide Ravelli,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 1476–1488, doi:10.3762/bjoc.16.123

• sulfonyl radical, prone to start a tandem sulfonylation/annulation of vinyl azides [84]. Recently, the phenanthridine core was assembled through a radical cascade triggered by the trifluoromethylthiolation of N-(o-cyanobiaryl)acrylamides. The process occurred under visible-light irradiation (6 W blue LED

• heteroarylalkynes. Synthesis of noravicine (14.2a) and nornitidine (14.2b) alkaloids. Gram-scale synthesis of the alkaloid trisphaeridine (15.3). Synthesis of phenanthridines starting from vinyl azides. Synthesis of pyrido[4,3,2-gh]phenanthridines 17.5a–d through the radical trifluoromethylthiolation of N-(o

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• and vinyl azides 92 for the synthesis of azaheterocyles 93 (Scheme 20) [98]. This strategy could also be applied to the synthesis of the quaternary indole alkaloid and melinonine-E. Quinones play an important role in organic chemistry because of their unique structure. In 2013, Malayappasamy and co

• cyclopropanols and vinyl azides. Ag(I)-catalyzed oxidative ring-opening of cyclopropanols with quinones. Ag(I)-catalyzed oxidative ring-opening of cyclopropanols with heteroarenes. Cu(I)-catalyzed oxidative ring-opening/trifluoromethylation of cyclopropanols. Cu(I)-catalyzed oxidative ring-opening and

Continuous multistep synthesis of 2-(azidomethyl)oxazoles

• Thaís A. Rossa,
• Nícolas S. Suveges,
• Marcus M. Sá,
• David Cantillo and
• C. Oliver Kappe

Beilstein J. Org. Chem. 2018, 14, 506–514, doi:10.3762/bjoc.14.36

• , Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil 22941-909, Research Center Pharmaceutical Engineering GmbH (RCPE), Inffeldgasse 13, 8010 Graz, Austria 10.3762/bjoc.14.36 Abstract An efficient three-step protocol was developed to produce 2-(azidomethyl)oxazoles from vinyl azides in a

• continuous-flow process. The general synthetic strategy involves a thermolysis of vinyl azides to generate azirines, which react with bromoacetyl bromide to provide 2-(bromomethyl)oxazoles. The latter compounds are versatile building blocks for nucleophilic displacement reactions as demonstrated by their

• integration; vinyl azides; Introduction Oxazoles are an important class of five-membered aromatic heterocycles containing one oxygen and one nitrogen atom in their structures. The oxazole moiety is relatively stable and is found widely in nature [1][2][3]. Naturally occurring oxazoles include compounds with

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• -methacryloylbenzamides is similar and includes alkyl substituents on the nitrogen atom and electron-rich and poor aromatic moieties. Mao and Zhou applied vinyl azides for the radical cross-coupling with sodium sulfinate salts (Scheme 56) [95]. They observed that the azide moiety decomposes during the reaction (loss of

• N2) which triggers an intramolecular cyclization reaction via a nitrogen-centred radical intermediate to form sulfonylated phenanthridines. The reaction is photocatalyzed by [Ru(bpy)3]Cl2 under irradiation with blue LEDs and proceeds smoothly for a variety of substituted vinyl azides and sulfonyl

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• using 18O2; no reaction occurred under N2 instead of O2; K2S2O8 rather than O2 served as initiator; the radical CF3SO2• could either extrude SO2 to CF3• or react with O2 to re-initiate the radical chain process (Scheme 7). Vinyl azides were used by Liu and co-workers as precursors of α

• -trifluoromethylated ketones by reaction of CF3SO2Na under photoredox catalysis. The substrate scope was broad and the reaction proceeded with high functional group tolerance; indeed, aryl-, alkyl-, hetero-functionalised terminal as well as non-terminal vinyl azides 15 were compatible with the reaction conditions. In

Reaction of allene esters with Selectfluor/TMSX (X = I, Br, Cl) and Selectfluor/NH₄SCN: Competing oxidative/electrophilic dihalogenation and nucleophilic/conjugate addition

• A. Srinivas Reddy and
• Kenneth K. Laali

Beilstein J. Org. Chem. 2015, 11, 1641–1648, doi:10.3762/bjoc.11.180

• presence of phosphane catalysts an umpolung addition takes place, whereby the nucleophilic addition occurs inversely at the beta-gamma double bond [22][23]. Vinyl azides have been prepared by hydroazidation of allenyl esters through a Michael-type addition with high regio- and stereoselectivity [24

[3 + 2]-Cycloadditions of nitrile ylides after photoactivation of vinyl azides under flow conditions

• Stephan Cludius-Brandt,
• Lukas Kupracz and
• Andreas Kirschning

Beilstein J. Org. Chem. 2013, 9, 1745–1750, doi:10.3762/bjoc.9.201

• Stephan Cludius-Brandt Lukas Kupracz Andreas Kirschning Institute of Organic Chemistry, Leibniz University Hannover, Schneiderberg 1b, 30167 Hannover, Germany 10.3762/bjoc.9.201 Abstract The photodenitrogenation of vinyl azides to 2H-azirines by using a photoflow reactor is reported and compared

• from the corresponding vinyl azide. Keywords: azirines; cycloaddition; flow chemistry; flow reactors; inductive heating; nitrile ylides; photochemistry; vinyl azides; Introduction Recently, photochemistry has seen a renaissance despite the fact that under batch conditions specialized reaction vessels

• photoinduced activation of vinyl azides 1, which gives rise to 2H-azirines 2 via vinyl nitrenes after the loss of molecular nitrogen and subsequent ring-opening under photochemical conditions to provide the nitrile ylides 3 (Scheme 1). For recent examples for the use of azirines in organic syntheses please

Multistep flow synthesis of vinyl azides and their use in the copper-catalyzed Huisgen-type cycloaddition under inductive-heating conditions

• Lukas Kupracz,
• Jan Hartwig,
• Jens Wegner,
• Sascha Ceylan and
• Andreas Kirschning

Beilstein J. Org. Chem. 2011, 7, 1441–1448, doi:10.3762/bjoc.7.168

• Lukas Kupracz Jan Hartwig Jens Wegner Sascha Ceylan Andreas Kirschning Institute of Organic Chemistry, Leibniz University Hannover, Schneiderberg 1b, 30167 Hannover, Germany 10.3762/bjoc.7.168 Abstract The multistep flow synthesis of vinyl azides and their application in the synthesis of

• vinyltriazoles is reported. The synthesis relies on a stable polymer-bound equivalent of iodine azide that serves to carry out 1,2-functionalization of alkenes in a telescope flow protocol. The intermediate 2-iodo azides are subjected to a DBU-mediated polymer-supported elimination step yielding vinyl azides in

• reactor. Keywords: flow reactor; inductive heating; iodine azide; polymer-supported reagents; vinyl azides; Introduction Azides are highly versatile organic functional groups and their preparation and their reactivity are well explored [1]. In contrast, the synthesis of vinyl azides is far away from