End group functionalization of poly(ethylene glycol) with phenolphthalein: towards star-shaped polymers based on supramolecular interactions

• Carolin Fleischmann,
• Hendrik Wöhlk and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 2263–2269, doi:10.3762/bjoc.10.235

• and Discussion We herein describe the synthesis of the host and guest compound, which were further utilized for the preparation of star shaped polymers based on supramolecular interactions. The preparation of both, the host and the guest compound, occurred via 1,3-dipolar cycloaddition, in which the

N–O Cleavage reactions of heterobicycloalkene-fused 2-isoxazolines

• Jaipal R. Nagireddy,
• Geoffrey K. Tranmer,
• Emily Carlson and
• William Tam

Beilstein J. Org. Chem. 2014, 10, 2200–2205, doi:10.3762/bjoc.10.227

• these compounds (17, 18 and 19) was prepared in our laboratories by a combination of Diels–Alder cycloaddition and 1,3-dipolar cycloaddition reactions [21]. We found that the Raney nickel-mediated cleavage took place readily on 17 to yield a β-hydroxyketo-functionalized 7-oxanorbornane 20 (Scheme 3

Multicomponent reactions in nucleoside chemistry

• Mariola Koszytkowska-Stawińska and
• Włodzimierz Buchowicz

Beilstein J. Org. Chem. 2014, 10, 1706–1732, doi:10.3762/bjoc.10.179

• polyoxin C hydrochloride 105*HCl (Scheme 44) [121]. The reaction cascade involved thermal formation of the corresponding azomethine ylide from substrate 105*HCl and benzaldehyde, followed by 1,3-dipolar cycloaddition of the ylide to N-methylmaleimide. The formation of compound 107 as the only product was

Clicked and long spaced galactosyl- and lactosylcalix[4]arenes: new multivalent galectin-3 ligands

• Silvia Bernardi,
• Paola Fezzardi,
• Gabriele Rispoli,
• Stefania E. Sestito,
• Francesco Peri,
• Francesco Sansone and
• Alessandro Casnati

Beilstein J. Org. Chem. 2014, 10, 1672–1680, doi:10.3762/bjoc.10.175

• glycocalixarenes “Click Chemistry” [23] reactions are extensively used to conjugate (oligo)saccharides to macrocyclic structures due to the mild conditions and the high yields [24]. For the synthesis of glycocalixarenes the amino–isothiocyanate condensation [25][26][27][28][29][30] or the 1,3-dipolar cycloaddition

Triazol-substituted titanocenes by strain-driven 1,3-dipolar cycloadditions

• Andreas Gansäuer,
• Andreas Okkel,
• Lukas Schwach,
• Laura Wagner,
• Anja Selig and
• Aram Prokop

Beilstein J. Org. Chem. 2014, 10, 1630–1637, doi:10.3762/bjoc.10.169

• the synthesis of triazole-substituted titanocenes via strain-driven 1,3-dipolar cycloadditions between azide-functionalized titanocenes and cyclooctyne has been developed. It features the first synthesis of titanocenes containing azide groups. These compounds constitute ‘second-generation

• nucleophiles. We decided to address these issues by employing cationic amide-substituted titanocenes as building blocks and strain-driven 1,3-dipolar cycloadditions [34][35][36][37][38][39][40] as synthetic methodology for the preparation of such ‘second-generation’ functional titanocenes. This line of action

• seemed especially appealing for two reasons. First, the cationic amide titanocenes have already displayed interesting activity and therefore serve as our lead structures. Second, the strain-driven 1,3-dipolar cycloadditions have evolved as extremely mild reactions for the functionalization of complex

Carbohydrate PEGylation, an approach to improve pharmacological potency

• M. Eugenia Giorgi,
• Rosalía Agusti and
• Rosa M. de Lederkremer

Beilstein J. Org. Chem. 2014, 10, 1433–1444, doi:10.3762/bjoc.10.147

• others, free radical polymerization of C-6 of the glucosamine residues with poly(ethylenglycol) acrylate [58]; free-radical polymerization of C-1 of glucosamine with mPEG [59] and 1,3-dipolar cycloaddition between the azide of an N-azidated chitosan and mPEG derivatives containing a triazolyl moiety [60

A complete series of 6-deoxy-monosubstituted tetraalkylammonium derivatives of α-, β-, and γ-cyclodextrin with 1, 2, and 3 permanent positive charges

• Martin Popr,
• Simona Hybelbauerová and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2014, 10, 1390–1396, doi:10.3762/bjoc.10.142

• Huisgen 1,3-dipolar cycloaddition [30] (most popular ‘click reaction’) or the reduction to the amine. Our strategy involved the synthesis of the alkylation agent 1-azido-2-iodoethane (24) (Scheme 5) which would be used for the quaternization of the tertiary amine intermediate. The reaction sequence for

An economical and safe procedure to synthesize 2-hydroxy-4-pentynoic acid: A precursor towards ‘clickable’ biodegradable polylactide

• Quanxuan Zhang,
• Hong Ren and
• Gregory L. Baker

Beilstein J. Org. Chem. 2014, 10, 1365–1371, doi:10.3762/bjoc.10.139

• groups onto polymers via convenient ‘click’ reaction with organic azido molecules without PLA backbone degradation [17]. ‘Click’ chemistry [20], which is copper(I)-catalyzed 1,3-dipolar cycloaddition of azides and alkynes, has been developed and utilized in recent years as a powerful synthetic strategy

Site-selective covalent functionalization at interior carbon atoms and on the rim of circumtrindene, a C₃₆H₁₂ open geodesic polyarene

• Hee Yeon Cho,
• Ronald B. M. Ansems and
• Lawrence T. Scott

Beilstein J. Org. Chem. 2014, 10, 956–968, doi:10.3762/bjoc.10.94

• side electronically more favorable for a nucleophilic attack. Prato reaction Cycloadditions to the π-system constitute another major family of fullerene reactions. In particular, 1,3-dipolar reagents readily add to the 6:6-bond of fullerene C60, which acts as a good dipolarophile. Among such [3 + 2

N-Alkylated dinitrones from isosorbide as cross-linkers for unsaturated bio-based polyesters

• Oliver Goerz and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 902–909, doi:10.3762/bjoc.10.88

• unsaturated polyester was cross-linked by a 1,3-dipolar cycloaddition with the received dinitrones 10a/b. The 1,3-dipolar cycloaddition led to a strong change of the mechanical properties which were investigated by rheological measurements. Nitrones derived from methyl acrylate (3a) and methyl crotonate (3b

• ) were used as model systems and reacted with dimethyl itaconate to further characterize the 1,3-dipolaric cycloaddition. Keywords: bio-based polyesters; cross-linkers; dinitrones; 1,3-dipolar cycloaddition; isosorbide; Introduction Nitrones represent a class of compounds with a versatile use as

• electron spin traps [1] and in cycloaddition reactions [2]. As nitrones undergo 1,3-dipolar cycloadditions under mild conditions with a variety of unsaturated substances with a catalyst [3][4] or without a catalyst [5] they are important for the synthetic accessibility of five-membered heterocycles

Use of activated enol ethers in the synthesis of pyrazoles: reactions with hydrazine and a study of pyrazole tautomerism

• Denisa Tarabová,
• Stanislava Šoralová,
• Martin Breza,
• Marek Fronc,
• Wolfgang Holzer and
• Viktor Milata

Beilstein J. Org. Chem. 2014, 10, 752–760, doi:10.3762/bjoc.10.70

• ), 1,3-dipolar cycloaddition with diazo compounds as a source of N–N linkage, degradation of fused pyrazoles or rearrangement of other monocyclic heterocycles under chemical, thermal or photochemical conditions [4]. Upon reaction of hydrazine with symmetrical enol ethers, only a single product is formed

Copper–phenanthroline catalysts for regioselective synthesis of pyrrolo[3′,4′:3,4]pyrrolo[1,2-a]furoquinolines/phenanthrolines and of pyrrolo[1,2-a]phenanthrolines under mild conditions

• Rupankar Paira,
• Tarique Anwar,
• Maitreyee Banerjee,
• Yogesh P. Bharitkar,
• Shyamal Mondal,
• Sandip Kundu,
• Abhijit Hazra,
• Prakas R. Maulik and
• Nirup B. Mondal

Beilstein J. Org. Chem. 2014, 10, 692–700, doi:10.3762/bjoc.10.62

• -700032, India 10.3762/bjoc.10.62 Abstract A new series of pyrrolo[3′,4′:3,4]pyrrolo[1,2-a]furoquinolines/phenanthrolines and pyrrolo[1,2-a]phenanthrolines were efficiently built up from an 8-hydroxyquinoline derivative or phenanthroline via 1,3-dipolar cycloaddition reaction involving non-stabilized

• azomethine ylides, generated in situ from the parent furo[3,2-h]quinoliniums/phenanthroliums, in presence of a copper(II) chloride–phenanthroline catalytic system. The methodology combines general applicability with high yields. Keywords: copper(II) chloride–phenanthroline; 1,3-dipolar cycloaddition; furo

• [3,2-h]quinoliniums; phenanthroliums; pyrrolo[1,2-a]phenanthrolines; pyrrolo[3′,4′:3,4]pyrrolo[1,2-a]furoquinolines/phenanthrolines; Introduction The chemistry of the 1,3-dipolar cycloaddition has always been a fascinating undertaking especially when azomethine ylides are involved as the key component

Synthesis of chiral N-phosphinyl α-imino esters and their application in asymmetric synthesis of α-amino esters by reduction

• Yiwen Xiong,
• Haibo Mei,
• Lingmin Wu,
• Jianlin Han,
• Yi Pan and
• Guigen Li

Beilstein J. Org. Chem. 2014, 10, 653–659, doi:10.3762/bjoc.10.57

• esters [6][7][8][9][10]. Up to now, a series of nucleophilic substrates have been reported to react with α-imino esters, such as enamine [11][12][13][14], carbamate ammonium ylide [15], 1,3-dipolar cycle [16], boronic acid [17], acetylide [18], proparygylic anion [19] and ketene silyl acetal [20]. These

Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

• Gijs Koopmanschap,
• Eelco Ruijter and
• Romano V.A. Orru

Beilstein J. Org. Chem. 2014, 10, 544–598, doi:10.3762/bjoc.10.50

• -components that bear an additional alkene, alkyne or azide moiety and can be cyclized via either a deprotection–cyclization strategy, a ring-closing metathesis, a 1,3-dipolar cycloaddition or even via a sequence of multiple multicomponent reactions. The sequential IMCR-cyclization reactions can afford small

• subsequent transformations [19][22][26]. Examples of IMCR orthogonal species or functionalities are alkenes, alkynes and azides which may give the cyclic analogues via subsequent ring closing metathesis (RCM) or 1,3-dipolar cycloadditions. In contrast, protected functional groups first require a deprotection

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• -type reactions, hetero Diels–Alder reactions, 1,3-dipolar cycloadditions and nitroso aldol reactions [93]. The process was firstly accomplished with preformed aryl-substituted aldimines [94] and then developed as a MCR for less stable alkyl-substituted aldimines, which were prepared in situ from

• tautomerization. Instead, an Ag(I) complex based on BINAP and AgSbF6 was employed as a catalyst for the enantioselective 1,3-dipolar cycloaddition reaction of azomethine ylides and alkenes for the synthesis of pyrrolidines 81 and 82 (Scheme 38) [97]. The reaction was developed mainly as a two-component reaction

Additive-assisted regioselective 1,3-dipolar cycloaddition of azomethine ylides with benzylideneacetone

• Chuqin Peng,
• Jiwei Ren,
• Jun-An Xiao,
• Honggang Zhang,
• Hua Yang and
• Yiming Luo

Beilstein J. Org. Chem. 2014, 10, 352–360, doi:10.3762/bjoc.10.33

• Chuqin Peng Jiwei Ren Jun-An Xiao Honggang Zhang Hua Yang Yiming Luo School of Chemistry and Chemical Engineering, Central South University,Changsha, Hunan 410083, P. R. China 10.3762/bjoc.10.33 Abstract 1,3-Dipolar cycloadditions of isatins, benzylamine and benzylideneacetones were studied to

• 4-nitrobenzoic acid, respectively. The substituent effects on the regioselectivity were also investigated. Keywords: 1,3-dipolar cycloaddition; azomethine ylide; regioselectivity; spirooxindole; Introduction Spirooxindoles are important synthetic targets due to their significant biological

• employed as starting materials to conduct 1,3-dipolar cycloadditions to yield spirooxindole core structures [16][17][18][19][20]. Owing to the ease of preparation, the azomethine ylides generated from isatin with α-amino acids or amines were frequently chosen as important 1,3-dipolar intermediates to react

Synthesis of new enantiopure poly(hydroxy)aminooxepanes as building blocks for multivalent carbohydrate mimetics

• Léa Bouché,
• Maja Kandziora and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2014, 10, 213–223, doi:10.3762/bjoc.10.17

• reduction of the carbonyl group [43] and TBS cleavage, propargylic ether 18 was obtained (88% yield over two steps) [44]. The alkyne moiety provides options for further transformations, e.g. Sonogashira reactions, Glaser couplings or 1,3-dipolar cycloadditions (click reactions) [45]. We were also interested

Synthesis and biological activity of N-substituted-tetrahydro-γ-carbolines containing peptide residues

• Nadezhda V. Sokolova,
• Valentine G. Nenajdenko,
• Vladimir B. Sokolov,
• Daria V. Vinogradova,
• Elena F. Shevtsova,
• Ludmila G. Dubova and
• Sergey O. Bachurin

Beilstein J. Org. Chem. 2014, 10, 155–162, doi:10.3762/bjoc.10.13

• described the conjugation of N-substituted tetrahydro-γ-carbolines containing a terminal alkyne group 3a–d with various azidopeptides 5 (prepared by Ugi multicomponent reaction) through the Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition. The activity of the obtained compounds on rat liver mitochondria

The regioselective synthesis of spirooxindolo pyrrolidines and pyrrolizidines via three-component reactions of acrylamides and aroylacrylic acids with isatins and α-amino acids

• Tatyana L. Pavlovskaya,
• Fedor G. Yaremenko,
• Victoria V. Lipson,
• Svetlana V. Shishkina,
• Oleg V. Shishkin,
• Vladimir I. Musatov and
• Alexander S. Karpenko

Beilstein J. Org. Chem. 2014, 10, 117–126, doi:10.3762/bjoc.10.8

• aroylacrylic acids as dipolarophiles has been realized through a one-pot 1,3-dipolar cycloaddition protocol. Decarboxylation of 2'-aroyl-2-oxo-1,1',2,2',5',6',7',7a'-octahydrospiro[indole-3,3'-pyrrolizine]-1'-carboxylic acids is accompanied by cyclative rearrangement with formation of dihydropyrrolizinyl

• inhibitors [9][10]. The multicomponent 1,3-dipolar cycloaddition of azomethine ylides, generated in situ via decarboxylative condensation of isatins and α-amino acids with olefinic and acetylenic dipolarophiles, represents a key approach for the regio- and stereoselective construction of a variety of complex

• inhibitors there are compounds containing a pyrrolidine-2-one as a part of the spirocyclic system [34]. In the present work we report the synthesis of spirooxindolo pyrrolidines and pyrrolizidines by utilizing a 1,3-dipolar cycloaddition of hitherto uninvestigated acrylamides and aroylacrylic acids with

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

• Alexander O. Terent'ev,
• Dmitry A. Borisov,
• Vera A. Vil’ and
• Valery M. Dembitsky

Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6

• formation of the Criegee intermediate are followed by a 1,3-dipolar interaction of the peroxycarbenium ion with the double bond (82) to form dioxolane 83. The yield was not lower than 48% but no exact yield was reported (Scheme 24) [255]. The peroxycarbenium ions produced by the decomposition of 1,2,4

• involves several steps: the 1,3-dipolar cycloaddition of ozone to the double bond to form unstable 1,2,3-trioxolane 164 (so-called molozonide) that is followed by its decomposition to a peroxycarbenium ion and a carbonyl compound (Criegee intermediates). The 1,3-dipolar cycloaddition of the intermediates

Four-component reaction of cyclic amines, 2-aminobenzothiazole, aromatic aldehydes and acetylenedicarboxylate

• Hong Gao,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2013, 9, 2934–2939, doi:10.3762/bjoc.9.330

• 1,3-dipolar intermediate A. In the meantime, the condensation of the aromatic aldehyde with 2-aminobenzothiazole affords an aldimine B. Secondly, the nucleophilic addition of 1,3-dipole intermediate A to aldimine B gives an addition intermediate C. Thirdly, the intramolecular nucleophilic attack of

Less reactive dipoles of diazodicarbonyl compounds in reaction with cycloaliphatic thioketones – First evidence for the 1,3-oxathiole–thiocarbonyl ylide interconversion

• Valerij A. Nikolaev,
• Alexey V. Ivanov,
• Ludmila L. Rodina and
• Grzegorz Mlostoń

Beilstein J. Org. Chem. 2013, 9, 2751–2761, doi:10.3762/bjoc.9.309

• -oxathiole to alkene were performed at the DFT PBE1PBE/6-31G(d) level. Keywords: 1,3-dipolar electrocyclization; 1,5-dipolar electrocyclization; 1,3-oxathioles; thiocarbonyl ylides; thiiranes; thioketones; Introduction Aryl- and alkylsubstituted thioketones exhibit high 1,3-dipolar reactivity towards

• formation of these compounds can be rationalized by pathways presented in Scheme 2 [4][22]. 1) Pathway A implies the initial 1,3-dipolar cycloaddition between the diazo compound 2 and the С=S bond of thioketone 1 giving rise to 1,3,4-thiadiazoline 10. The latter is usually an unstable intermediate species

• intermediate 1,3,4-thiadiazoline or a diazonium zwitterion. Next, electrocyclization of the transient thiocarbonyl ylide leads to spirocyclic 1,3-oxathioles in yields of up to 88%. In similar reactions of diazomalonate 2e, a competitive process of 1,3-dipolar electrocyclization is observed. It led to the

Advancements in the mechanistic understanding of the copper-catalyzed azide–alkyne cycloaddition

• Regina Berg and
• Bernd F. Straub

Beilstein J. Org. Chem. 2013, 9, 2715–2750, doi:10.3762/bjoc.9.308

• but-2-ynedioate and phenyl azide at 100 °C in a sealed tube and suggested that regioisomeric triazoles were formed [1]. However, it was only in the 1960s that Huisgen recognized this type of reaction for its generality, scope and mechanism [2][3][4][5], and coined the term 1,3-dipolar cycloaddition

• a factor of up to 107 in comparison to Huisgen’s uncatalyzed procedure [13][14]. Since Meldal and Sharpless had first reported this copper-catalyzed variant of Huisgen’s 1,3-dipolar cycloaddition, a myriad of protocols employing different catalyst systems has been described. It is essential for the

Synthetic scope and DFT analysis of the chiral binap–gold(I) complex-catalyzed 1,3-dipolar cycloaddition of azlactones with alkenes

• María Martín-Rodríguez,
• Luis M. Castelló,
• Carmen Nájera,
• José M. Sansano,
• Olatz Larrañaga,
• Abel de Cózar and
• Fernando P. Cossío

Beilstein J. Org. Chem. 2013, 9, 2422–2433, doi:10.3762/bjoc.9.280

• , Universidad del País Vasco, Apdo. 1072, E-20018 San Sebastián, Spain IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain 10.3762/bjoc.9.280 Abstract The 1,3-dipolar cycloaddition between glycine-derived azlactones with maleimides is efficiently catalyzed by the dimeric chiral complex [(Sa

• : asymmetric catalysis; DFT; 1,3-dipolar cycloaddition; gold catalysis; NICS; NTR; oxazolones; prolines; Introduction The synthesis of α-amino acids employing an α-amino carbonyl template constitutes the most straightforward route to introduce the α-side chain [1]. As a valid example, oxazol-5-(4H)-ones

• electrophilic alkenes have not been exploited. Toste´s group published an efficient 1,3-dipolar cycloaddition (1,3-DC) between alanine, phenylalanine and allylglycine derived azlactones with maleimides and acrylates employing dimetallic (S)-Cy-Segphos(AuOBz)2 complex 1 as a catalyst (2 mol %) in the absence of

Synthesis of enantiopure sugar-decorated six-armed triptycene derivatives

• Paola Bonaccorsi,
• Maria Luisa Di Gioia,
• Antonella Leggio,
• Lucio Minuti,
• Teresa Papalia,
• Carlo Siciliano,
• Andrea Temperini and
• Anna Barattucci

Beilstein J. Org. Chem. 2013, 9, 2410–2416, doi:10.3762/bjoc.9.278

• is the first example of six-armed carbohydrate-substituted triptycenes, which appear as promising candidates for the development of new supramolecular systems with specific properties. Results and Discussion The Huisgen 1,3-dipolar cycloaddition reaction, which represents the key step of click