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

Advances in synthetic approach to and antifungal activity of triazoles

• Kumari Shalini,
• Nitin Kumar,
• Sushma Drabu and
• Pramod Kumar Sharma

Beilstein J. Org. Chem. 2011, 7, 668–677, doi:10.3762/bjoc.7.79

• occupies the most important place in the treatment of fungal diseases. The triazole derivatives noted below were synthesized by various groups and show antifungal activity. Novel 1,2,3-triazole-linked with β-lactam–bile acid conjugates were prepared via 1,3-dipolar cycloaddition reactions of azido β

Synthesis of cross-conjugated trienes by rhodium-catalyzed dimerization of monosubstituted allenes

• Tomoya Miura,
• Tsuneaki Biyajima,
• Takeharu Toyoshima and
• Masahiro Murakami

Beilstein J. Org. Chem. 2011, 7, 578–581, doi:10.3762/bjoc.7.67

• used for consecutive double [4 + 2] cycloaddition reactions [2][3][4] to provide a rapid access to polycyclic carbon frameworks. Thus, a number of methods for the preparation of the parent 3-methylenepenta-1,4-diene [5] and its substituted derivatives [6][7][8][9][10][11][12][13][14][15][16][17] has

Brønsted acid-promoted azide–olefin [3 + 2] cycloadditions for the preparation of contiguous aminopolyols: The importance of disiloxane ring size to a diastereoselective, bidirectional approach to zwittermicin A

• Hubert Muchalski,
• Ki Bum Hong and
• Jeffrey N. Johnston

Beilstein J. Org. Chem. 2010, 6, 1206–1210, doi:10.3762/bjoc.6.138

• cycloaddition reactions exist, they rely on intramolecular azide delivery under thermal conditions [15][16][17][18][19][20][21]. Examples of substrate control in an acid-catalyzed intermolecular reaction of azides with alkenes are limited [22]. We report our initial study of the intermolecular

• , diastereoselective sequence of two [3 + 2] cycloaddition reactions promoted by triflic acid where the large 1,3-diol protecting group – the 1,1,3,3-tetraisopropoxydisiloxanylidene group (TIPDS) – plays a crucial role in facial discrimination. Results and Discussion Our approach to the preparation of enantiomerically

Acid catalyzed cyclodimerization of 2,2-bis(trifluoromethyl)-4-alkoxy-oxetanes and -thietanes. Synthesis of 2,2,6,6-tetrakis(trifluoromethyl)-4,8-dialkoxy-1,5-dioxocanes and 3,3,7,7-tetrakis(trifluoromethyl)-9-oxa-2,6-dithia-bicyclo[3.3.1]nonane

• Viacheslav A. Petrov and
• Will Marshall

Beilstein J. Org. Chem. 2010, 6, No. 46, doi:10.3762/bjoc.6.46

• process itself is simple, reproducible and provides easy access to this new group of stable polyfluorinated 1,5-dioxocanes. It should also be pointed out, that examples of electrophilic [4 + 4] cycloaddition reactions are extremely rare and limited to two examples: the reaction of the oxetane (derived

An expedient and new synthesis of pyrrolo[1,2-b]pyridazine derivatives

• Rajeshwar Reddy Sagyam,
• Ravinder Buchikonda,
• Jaya Prakash Pitta,
• Himabindu Vurimidi,
• Pratap Reddy Padi and
• Mahesh Reddy Ghanta

Beilstein J. Org. Chem. 2009, 5, No. 66, doi:10.3762/bjoc.5.66

• acid hydrazide with 3-bromo-1,1,3-tricyano-2-phenylpropene [17]; and the reaction between 3-chloropyridazines with propargylic alcohol in the presence of Pd(PPh3)2Cl2–CuI with diethylamine as the reaction medium [18][19]. The second approach is based on cycloaddition reactions, such as the

Synthesis and Diels–Alder cycloaddition reaction of norbornadiene and benzonorbornadiene dimers

• Bilal Nişancı,
• Erdin Dalkılıç,
• Murat Güney and
• Arif Daştan

Beilstein J. Org. Chem. 2009, 5, No. 39, doi:10.3762/bjoc.5.39

• indistinguishable. To determine which is which, cycloaddition reactions of dimers are more informative. Dimers 7 and 16 give symmetric addition products 11, 12 and 18, 19, whereas the reaction of dimers 8 and 17 resulted in the formation of unsymmetrical products 13, 14 and 20, 21. For the symmetric addition

• ). Numbering of carbon atoms and description of possible structures for dimers 11–14 and 18–21. Synthesis of starting materials 4 and 5. Synthesis and Diels–Alder cycloaddition reactions of dimers 7 and 8. Synthesis and Diels–Alder cycloaddition reactions of dimers 16 and 17. Acknowledgments This work has

Aroylketene dithioacetal chemistry: facile synthesis of 4-aroyl- 3-methylsulfanyl- 2-tosylpyrroles from aroylketene dithioacetals and TosMIC

• H. Surya Prakash Rao and
• S. Sivakumar

Beilstein J. Org. Chem. 2007, 3, No. 31, doi:10.1186/1860-5397-3-31

• heterocyclic systems, examples of their participation in the cycloaddition reactions are rare. In continuation of our interest on ketene acetals [5][6][7] we considered that 1,3-dipolar cycloaddition of the anion generated from the von Leusen's reagent (p-tolylsulfonyl)methyl isocyanide (TosMIC) 2 to AKDTAs 1

The use of silicon- based tethers for the Pauson- Khand reaction

• Adrian P. Dobbs,
• Ian J. Miller and
• Saša Martinović

Beilstein J. Org. Chem. 2007, 3, No. 21, doi:10.1186/1860-5397-3-21

• has shown that for cycloaddition reactions to occur, the non-reactive substituents around the silicon centre must be more bulky than the Me or Ph groups employed in these studies. Denmark's work demonstrated that the angles at the silicon centre between the two 'arms' of the silyl ether can be up to

High stereoselectivity on low temperature Diels- Alder reactions

• Luiz Carlos da Silva Filho,
• Valdemar Lacerda Júnior,
• Mauricio Gomes Constantino,
• Gil Valdo José da Silva and
• Paulo Roberto Invernize

Beilstein J. Org. Chem. 2005, 1, No. 14, doi:10.1186/1860-5397-1-14

• , usually AlCl3, could be used to enhance the reactivity of these poor dienophiles. [1][2][3][4] Particularly the cycloenones are desirable dienophiles, because their cycloaddition reactions are a remarkable tool for the synthesis of octalones and related bicyclic olefinic ketones (e.g., decaline-based

• attack. The resulting lowering of the activation energy usually leads to an enhancement of stereo- and regioselectivity [7]. It was also soon realized that the modifications in the cycloaddition reactions parameters should depend on the Lewis acids used, and a number of authors have performed comparison