[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

• cycloaddition reactions. They are commonly formed through three routes which are a) the addition of electrophilic carbenes to nitriles, b) the dehydrochlorination of imidoyl chlorides, and c) the photochemical ring opening of strained 2H-azirines 2 [2][3][4][5]. The latter route can be initiated by the

Aerobic radical multifunctionalization of alkenes using tert-butyl nitrite and water

• Daisuke Hirose and
• Tsuyoshi Taniguchi

Beilstein J. Org. Chem. 2013, 9, 1713–1717, doi:10.3762/bjoc.9.196

• useful methods because they can provide a shortcut to desired products. Various methods used widely, such as organometallic reactions, cycloaddition reactions and multicomponent reactions, are utilized for multifunctionalization [1][2][3][4][5]. If direct functionalization reactions of inactivated bonds

The rapid generation of isothiocyanates in flow

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 1613–1619, doi:10.3762/bjoc.9.184

• purification of reaction sequences [40][41][42][43][44]. In addition they have been successfully utilised in order to render dipolar cycloaddition reactions involving azomethine ylides [45][46] as well as nitrile oxides [47][48] more practical for generating important heterocyclic scaffolds such as

Efficient continuous-flow synthesis of novel 1,2,3-triazole-substituted β-aminocyclohexanecarboxylic acid derivatives with gram-scale production

• Sándor B. Ötvös,
• Ádám Georgiádes,
• István M. Mándity,
• Lóránd Kiss and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2013, 9, 1508–1516, doi:10.3762/bjoc.9.172

• acid derivatives in a simple and efficient continuous-flow procedure is reported. The 1,3-dipolar cycloaddition reactions were performed with copper powder as a readily accessible Cu(I) source. Initially, high reaction rates were achieved under high-pressure/high-temperature conditions. Subsequently

Controlled synthesis of poly(3-hexylthiophene) in continuous flow

• Helga Seyler,
• Jegadesan Subbiah,
• David J. Jones,
• Andrew B. Holmes and
• Wallace W. H. Wong

Beilstein J. Org. Chem. 2013, 9, 1492–1500, doi:10.3762/bjoc.9.170

• mixing of reagents, boosting reaction rates, and safe handling of reactive intermediates. Using a commercial continuous-flow tube reactor [19], we have already demonstrated multigram synthesis of fullerene derivatives by cycloaddition reactions [11] as well as rapid conjugated-polymer synthesis using

Diastereoselective synthesis of nitroso acetals from (S,E)-γ-aminated nitroalkenes via multicomponent [4 + 2]/[3 + 2] cycloadditions promoted by LiCl or LiClO₄

• Leandro Lara de Carvalho,
• Robert Alan Burrow and
• Vera Lúcia Patrocinio Pereira

Beilstein J. Org. Chem. 2013, 9, 838–845, doi:10.3762/bjoc.9.96

• diffraction experiment. Keywords: chiral heterodiene; hetero-Diels–Alder reaction; pyrrolizidin-3-one; solvent effect; tandem reaction; Introduction Conjugated nitroalkenes play an important role in cycloaddition reactions providing useful nitrogenated cycloadducts with varied synthetic applications (Scheme

• hydrophobic effect can lead the reaction partners to collapse to a TS that is less hydrophobic and less destabilized than the initial state, promoting an increase in the reaction rate [17][28][29]. Aiming to improve the efficiency of the cycloaddition reactions, LiCl or LiClO4 solutions were used as a

• good reaction medium causing a large enhancement in the reaction rate. Moreover, the role of the lithium salt solution in the cycloaddition reactions is still controversial and has been the subject of discussion. The increase of the solvent internal pressure, caused by the presence of lithium salt, and

Titanium-mediated reductive cross-coupling reactions of imines with terminal alkynes: An efficient route for the synthesis of stereodefined allylic amines

• Kebin Mao,
• Guoqin Fan,
• Yuanhong Liu,
• Shi Li,
• Xu You and
• Dan Liu

Beilstein J. Org. Chem. 2013, 9, 621–627, doi:10.3762/bjoc.9.69

• organic chemistry and their synthesis is an important industrial and synthetic goal [1][2][3][4]. The two functionalities in the allylic amine fragment, i.e., the nucleophilic amino group and the alkene, can ideally participate in cycloaddition reactions [5][6], condensation reactions [7], nucleophilic

Microwave-assisted three-component domino reaction: Synthesis of indolodiazepinotriazoles

• Rajesh K. Arigela,
• Sudhir K. Sharma,
• Brijesh Kumar and
• Bijoy Kundu

Beilstein J. Org. Chem. 2013, 9, 401–405, doi:10.3762/bjoc.9.41

• 1,3-dipolar cycloaddition reactions have been also applied by us and others with the view to synthesize triazole-annulated polyheterocycles. Although these cyclizations have been successfully carried out in either one-pot [22][23][24] or multistep format [25][26][27][28], reports involving their

Towards a biocompatible artificial lung: Covalent functionalization of poly(4-methylpent-1-ene) (TPX) with cRGD pentapeptide

• Lena Möller,
• Christian Hess,
• Jiří Paleček,
• Yi Su,
• Axel Haverich,
• Andreas Kirschning and
• Gerald Dräger

Beilstein J. Org. Chem. 2013, 9, 270–277, doi:10.3762/bjoc.9.33

• ) F 1s core level, (c) N 1s core level. UV spectra of TPX 8c and 8d functionalized with fluorescein revealing the efficiency of the 1,3-dipolar cycloaddition reactions on modified TPX membranes. Continuous line: 8d; dotted line: 8c; dashed line: substrate for Huisgen-type “click” reaction 7a. Cell

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

• -containing tethers. Preparatively the bisallenes are especially useful in isomerization and cycloaddition reactions of all kinds leading to the respective target molecules with high atom economy and often in high yield. Bisallenes are hence substrates for generating molecular complexity in a small number of

Iridium-catalyzed intramolecular [4 + 2] cycloadditions of alkynyl halides

• Andrew Tigchelaar and
• William Tam

Beilstein J. Org. Chem. 2012, 8, 1765–1770, doi:10.3762/bjoc.8.201

• , including homogeneous hydrogenation [1][2], C–H activation [3][4][5], asymmetric ring-opening reactions [6], and a variety of cycloisomerizations [7][8][9][10], and cycloadditions [11][12][13][14][15][16][17][18][19][20]. Traditionally these types of cycloisomerization and cycloaddition reactions are

Organocatalytic cascade aza-Michael/hemiacetal reaction between disubstituted hydrazines and α,β-unsaturated aldehydes: Highly diastereo- and enantioselective synthesis of pyrazolidine derivatives

• Zhi-Cong Geng,
• Jian Chen,
• Ning Li,
• Xiao-Fei Huang,
• Yong Zhang,
• Ya-Wen Zhang and
• Xing-Wang Wang

Beilstein J. Org. Chem. 2012, 8, 1710–1720, doi:10.3762/bjoc.8.195

• ], and moreover, pyrazolidines can also be oxidized to afford pyrazolines [8][9][10][11][12] and pyrazoles [13][14][15]. The pyrazolidine structural unit is commonly constructed by [3 + 2] cycloaddition reactions using hydrazones [16][17][18][19][20][21][22][23] or azomethine amines [24][25][26][27] as

Highly enantioselective access to cannabinoid-type tricyles by organocatalytic Diels–Alder reactions

• Stefan Bräse,
• Nicole Volz,
• Franziska Gläser and
• Martin Nieger

Beilstein J. Org. Chem. 2012, 8, 1385–1392, doi:10.3762/bjoc.8.160

• published total synthesis of Taxol (2) by Nicolaou. Two different [4 + 2]-cycloaddition reactions were applied to set up each of the two six-membered rings of the target molecule [9][10]. As a final example, Dynemicin A (3) should be mentioned, which is an enediyne consisting of a complex heterocyclic

• skeleton and a network of sensitive functional groups, exhibiting antitumor and antibiotic activity [11]. Three independent research groups (Schreiber, Myers and Danishefsky) successfully applied [4 + 2]-cycloaddition reactions in elegant and divergent strategies to reach the target molecule [12][13][14

Synthesis and in silico screening of a library of β-carboline-containing compounds

• Kay M. Brummond,
• John R. Goodell,
• Matthew G. LaPorte,
• Lirong Wang and
• Xiang-Qun Xie

Beilstein J. Org. Chem. 2012, 8, 1048–1058, doi:10.3762/bjoc.8.117

• not be identified (see spectral data in Supporting Information File 1). Aryl-substituted alkynones 9{1,5}–9{1,8} were not available for the molybdenum-mediated cyclocarbonylation process due to competing [2 + 2] cycloaddition reactions (Table 2). The majority of these β-carboline-containing products

Thiophene-based donor–acceptor co-oligomers by copper-catalyzed 1,3-dipolar cycloaddition

• Stefanie Potratz,
• Amaresh Mishra and
• Peter Bäuerle

Beilstein J. Org. Chem. 2012, 8, 683–692, doi:10.3762/bjoc.8.76

• . Conclusion In summary, a series of novel thiophene-1,2,3-triazole co-oligomers was synthesized in good to excellent yields by a three-component two-step procedure using copper-catalyzed [3 + 2]-Huisgen cycloaddition reactions. Spectroscopic and redox properties of selected donor–acceptor–donor derivatives

• to give a dithienyl-1,2,3-triazole co-oligomer 5. See Table 1 for detailed conditions. Synthesis of 1,4-bis[4-(thiophen-2-yl)-1H-1,2,3-triazol-1-yl]-benzene 21. Variation of solvent mixture and temperature in Cu(I)-catalyzed cycloaddition reactions of 2-iodothiophene (3) and 2-ethynylthiophene (4) to

Aryl nitrile oxide cycloaddition reactions in the presence of pinacol boronic acid ester

• Sarah L. Harding,
• Sebastian M. Marcuccio and
• G. Paul Savage

Beilstein J. Org. Chem. 2012, 8, 606–612, doi:10.3762/bjoc.8.67

• bonds, and 1,3-dipolar cycloaddition reactions to construct five-membered heterocycles are both powerful tools for assembling organic molecules. Used in combination, these tools offer great flexibility for strategies such as diversity-oriented synthesis [1], solution-phase combinatorial libraries [2

• developing a mild method for the introduction of a nitrile oxide functionality in the presence of an arylboronic ester, allowing subsequent elaboration. We herein report the synthesis and 1,3-dipolar cycloaddition reactions of 4-pinacolatoboron benzonitrile oxide 1. Results and Discussion Several reports of

• 1,3-dipolar cycloaddition reactions of nitrile oxides to vinylboronate esters [28][29] and alkynylboronate esters [30][31] have recently appeared. In each case the nitrile oxide was either isolated first (this procedure is limited to hindered nitrile oxides, such as 2,4,6-trimethylbenzonitrile oxide

Azobenzene dye-coupled quadruply hydrogen-bonding modules as colorimetric indicators for supramolecular interactions

• Yagang Zhang and
• Steven C. Zimmerman

Beilstein J. Org. Chem. 2012, 8, 486–495, doi:10.3762/bjoc.8.55

• solid in 71% yield. The product was assigned as the 1,4-substituted triazole by analogy to that seen in other such cycloaddition reactions [56]. Azobenzene-coupled DAN modules 5, 8, and 10 are bright orange–red in color and azobenzene-coupled DeUG modules 12 and 18 are orange–yellow in color (Figure 3

Intramolecular carbenoid ylide forming reactions of 2-diazo-3-keto-4-phthalimidocarboxylic esters derived from methionine and cysteine

• Marc Enßle,
• Stefan Buck,
• Roland Werz and
• Gerhard Maas

Beilstein J. Org. Chem. 2012, 8, 433–440, doi:10.3762/bjoc.8.49

• NOESY NMR experiment indicated the correlation shown in Scheme 6. Intramolecular [3 + 2]-cycloaddition reactions of a carbonyl ylide with a nonactivated but suitably positioned olefinic bond have been known for some time [3][27][28][29][30][31][32][33][34][35] and can be used for the construction of

• substructure. Trapping of carbonyl ylides with dipolarophiles In situ generated carbonyl ylides can be intercepted not only in intramolecular (as discussed above) but also in intermolecular [3 + 2] cycloaddition reactions (see, for example, [3][18][19][20][41][42]). By analogy with other 2-diazo-3-oxo-4

• , yielding either a cyclic sulfonium ylide or a six-ring carbonyl ylide. In fact, it has been found that Rh(II)-catalyzed dediazoniation of α-diazo-β-ketoesters with γ-phthalimido [18][19] or related [20] substituents gives rise to cyclic carbonyl ylides, which were trapped by intermolecular cycloaddition

Synthesis of 2-amino-3-arylpropan-1-ols and 1-(2,3-diaminopropyl)-1,2,3-triazoles and evaluation of their antimalarial activity

• Matthias D’hooghe,
• Stéphanie Vandekerckhove,
• Karen Mollet,
• Karel Vervisch,
• Stijn Dekeukeleire,
• Liesbeth Lehoucq,
• Carmen Lategan,
• Peter J. Smith,
• Kelly Chibale and
• Norbert De Kimpe

Beilstein J. Org. Chem. 2011, 7, 1745–1752, doi:10.3762/bjoc.7.205

• water-induced ring opening of nonactivated cis- and trans-2-aryl-3-(hydroxymethyl)aziridines and with respect to the synthesis and use of 1-arylmethyl-2-(azidomethyl)aziridines for azide-alkyne cycloaddition reactions. From a biological viewpoint, most of these compounds exhibited weak antiplasmodial

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

• hybrids of a number of mesomeric ionic structures (Figure 1). One of the most characteristic reactions of sydnones is the intermolecular 1,3-dipolar cycloaddition. In the presence of acetylenic or ethylenic dipolarophiles, sydnones undergo cycloaddition reactions, which can be induced thermally [4][6][7

• , giving polycyclic compound 14, while the sydnone moiety in the cis isomer 3b gives polycyclic compound 15. Stilbene-methylene-sydnones are useful substrates for photochemical and thermal intramolecular [3 + 2] cycloaddition reactions to heteropolycyclic compounds. Resonance structures of the sydnone ring

Asymmetric synthesis of quaternary aryl amino acid derivatives via a three-component aryne coupling reaction

• Elizabeth P. Jones,
• Peter Jones,
• Andrew J. P. White and
• Anthony G. M. Barrett

Beilstein J. Org. Chem. 2011, 7, 1570–1576, doi:10.3762/bjoc.7.185

• Arynes are exceptionally versatile reactive intermediates in organic synthesis. Not only are they able to participate in cycloaddition reactions, they also readily undergo addition reactions with nucleophiles, and the resultant aryl anions may be protonated or undergo alternative transformations [1][2][3

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

• to polycyclic products. Importantly, they generally involve the simple addition of two or more molecules, thereby being atom economical, and take place with high regio- and stereocontrol [2][3]. Unfortunately, the realm of classical cycloaddition reactions is relatively small and restricted to

• , cobalt, nickel or palladium catalysts [4]. In recent years, however, platinum and particularly gold complexes have also emerged as excellent catalysts for the promotion of novel types of cycloaddition reactions, usually involving non-activated unsaturated systems (e.g., alkynes, allenes, alkenes or 1,3

• (e.g., ligand–Au+). In this context, a number of research groups have in recent years embarked on the design and development of new cycloaddition reactions promoted by gold(I) and (III) catalysts, and hence the field has experienced a remarkable expansion. In the following section, we summarize some of

Cationic gold(I) axially chiral biaryl bisphosphine complex-catalyzed atropselective synthesis of heterobiaryls

• Tetsuro Shibuya,
• Kyosuke Nakamura and
• Ken Tanaka

Beilstein J. Org. Chem. 2011, 7, 944–950, doi:10.3762/bjoc.7.105

• synthesis [1][2][3][4] has attracted significant interest due to its great utility in asymmetric catalysis and natural product synthesis. In 2004, three research groups, including ours, independently reported transition-metal catalyzed asymmetric [2 + 2 + 2] cycloaddition reactions to produce axially chiral

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

• examples of sp3 C–H bond insertion via a cationic gold(I)–carbenoid intermediate. 4.3 Cycloadditions Intramolecular [M + N]-type cycloaddition reactions are powerful tools for accessing complex molecular frameworks [98]. Several gold-catalyzed [3 + 2] [99], [4 + 2] [100][101][102][103][104][105], and [4

• + 3] [106][107][108] cycloaddition reactions have been developed in last 3 years. Treatment of 1-aryl-1-allen-6-enes 220 with [PPh3AuCl]/AgSbF6 (5 mol %) in CH2Cl2 at 25 °C led to intramolecular [3 + 2] cycloadditions to afford cis-fused dihydrobenzo[a]fluorenes 221 efficiently and selectively [99

• 222, while the stereochemistry of the reaction depends on the ring size. In some gold(I)-catalyzed cycloaddition reactions, regiochemistry of the product is controlled by the ligand [100][101]. For example, the triphenylphosphinegold(I)-catalyzed reaction of allene–diene 224 provided a 2:1 mixture of

Synthetic applications of gold-catalyzed ring expansions

• David Garayalde and
• Cristina Nevado

Beilstein J. Org. Chem. 2011, 7, 767–780, doi:10.3762/bjoc.7.87

• ]-cycloadditions are just some of the relevant available methods employed by organic chemists to increase the molecular complexity of products originating from rather straightforward starting materials. In contrast to the vast number of precedents involving Rh-catalyzed [4 + 3]-cycloaddition reactions to form 7