Hetero-Diels–Alder reactions of hetaryl and aryl thioketones with acetylenic dienophiles

• Grzegorz Mlostoń,
• Paulina Grzelak,
• Maciej Mikina,
• Anthony Linden and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2015, 11, 576–582, doi:10.3762/bjoc.11.63

• offers some advantages, especially in the case of cycloaddition reactions [18]. To the best of our knowledge, reactions of thioketones under high-pressure conditions have never been studied. After a series of optimization experiments, a solution of 1a and 2a in a molar ratio of 1:2 in toluene was placed

On the strong difference in reactivity of acyclic and cyclic diazodiketones with thioketones: experimental results and quantum-chemical interpretation

• Andrey S. Mereshchenko,
• Alexey V. Ivanov,
• Viktor I. Baranovskii,
• Grzegorz Mloston,
• Ludmila L. Rodina and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2015, 11, 504–513, doi:10.3762/bjoc.11.57

• of DDC 1 with thiobenzophenone (2a). Reactions of the intermediate thiocarbonyl ylide 7'd via competative 1,5-EC (a) or 1,3-EC (b) followed by desulfurization of thiirane 4'd into alkene 5'd. Calculated relative energies (in kcal·mol−1) and relative reaction rates for cycloaddition reactions of diazo

Functionalized branched EDOT-terthiophene copolymer films by electropolymerization and post-polymerization “click”-reactions

• Miriam Goll,
• Adrian Ruff,
• Erna Muks,
• Felix Goerigk,
• Beatrice Omiecienski,
• Ines Ruff,
• Rafael C. González-Cano,
• Juan T. Lopez Navarrete,
• M. Carmen Ruiz Delgado and
• Sabine Ludwigs

Beilstein J. Org. Chem. 2015, 11, 335–347, doi:10.3762/bjoc.11.39

• on the reaction with the monomer EDOT-N3 and obtained the product EDOT-clickSO3Na in high yield. For 1H NMR and IR-spectra we refer to Figure S3 and Figure S4 in Supporting Information File 1. Figure 3A depicts the synthesis of the cycloaddition-reactions of the copolymer films P(EDOT-N3-co-3T)-1:1

Enhancing the reactivity of 1,2-diphospholes in cycloaddition reactions

• Almaz Zagidullin,
• Vasili Miluykov,
• Elena Oshchepkova,
• Artem Tufatullin,
• Olga Kataeva and
• Oleg Sinyashin

Beilstein J. Org. Chem. 2015, 11, 169–173, doi:10.3762/bjoc.11.17

• (R = CN, COOEt, OMe, CH2OEt) results in corresponding 1-alkyl-3,4,5-triphenyl-1,2-diphospholes (alkyl = CH2CN (1a), CH2COOEt (1b), CH2OMe (1c), and (CH2)2OEt (1d)), which spontaneously undergo the intermolecular [4 + 2] cycloaddition reactions at room temperature to form the mixture of the

• , phosphinidenes, etc. [2]. At the same time, the presence of electron-withdrawing substituents (cyano-, alkoxy-, or halo-) at the phosphorus atom reduces the aromaticity of the monophosphole ring and facilitates cycloaddition reactions resulting in novel 7-phosphanorbornenes [5][6], which was verified by

• at room temperature for a few hours. 1,2-Diphosphole 1d is more stable and no cycloaddition was observed upon heating in toluene. Upon standing, the diphospholes 1a–c undergo spontaneous [4 + 2] cycloaddition reactions leading to a mixture of cycloadducts (Scheme 2). The 31P NMR spectra of the

Synthetic strategies for the fluorescent labeling of epichlorohydrin-branched cyclodextrin polymers

• Milo Malanga,
• Mihály Bálint,
• István Puskás,
• Kata Tuza,
• Tamás Sohajda,
• László Jicsinszky,
• Lajos Szente and
• Éva Fenyvesi

Beilstein J. Org. Chem. 2014, 10, 3007–3018, doi:10.3762/bjoc.10.319

• (i.e., RBIT, NBF-Cl, FITC) or nucleophilic fluorescent dye (i.e., coumarin) into the polymers, respectively. The key intermediate azido-modified polymers have been used as precursor of the amino-modified polymers, but they can be considered as versatile substrates for cycloaddition reactions as well

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

Synthesis of nanodiamond derivatives carrying amino functions and quantification by a modified Kaiser test

• Gerald Jarre,
• Steffen Heyer,
• Elisabeth Memmel,
• Thomas Meinhardt and
• Anke Krueger

Beilstein J. Org. Chem. 2014, 10, 2729–2737, doi:10.3762/bjoc.10.288

• 0.15 mmol g−1 for the Diels–Alder reaction of the non-functionalized ortho-quinodimethane [11] proves that a significantly increased grafting is observed using the pyrazine derivative. So far, the reported cycloaddition reactions of ortho-quinodimethanes leading to the grafting of aromatic rings by

New highlights of the syntheses of pyrrolo[1,2-a]quinoxalin-4-ones

• Emilian Georgescu,
• Alina Nicolescu,
• Florentina Georgescu,
• Florina Teodorescu,
• Daniela Marinescu,
• Ana-Maria Macsim and
• Calin Deleanu

Beilstein J. Org. Chem. 2014, 10, 2377–2387, doi:10.3762/bjoc.10.248

• -benzylbenzimidazoles, phenacyl bromides and non-symmetrical activated alkynes in presence of propenoxide or 1,2-epoxybutane used as acid scavenger and reaction solvent [16]. These results prompted us to further investigate 1,3-cycloaddition reactions of 1-substituted 3-(alkoxycarbonylmethyl)benzimidazolium ylides with

• various dipolarophiles under the same reaction conditions, aiming to explore the generality of the reaction. The previously reported data on 1,3-cycloaddition reactions of 1-substituted 3-(alkoxycarbonylmethyl)benzimidazolium ylides with various dipolarophiles are rather contradictory. Thus, 1-alkyl-3

• cycloadducts 8. In order to explain the above mentioned results, we investigated the influence of reaction conditions on the ratio of the final reaction products 4 and 5 in 1,3-dipolar cycloaddition reactions of the 1-benzyl-3-(ethoxycarbonylmethyl)benzimidazolium bromide 6 (R = H, R1 = benzyl) with ethyl

Synthesis of 2-trifluoromethylpyrazolo[5,1-a]isoquinolines via silver triflate-catalyzed or electrophile-mediated one-pot tandem reaction

• Xiaoli Zhou,
• Meiling Liu,
• Puying Luo,
• Yingjun Lai,
• Tangtao Yang and
• Qiuping Ding

Beilstein J. Org. Chem. 2014, 10, 2286–2292, doi:10.3762/bjoc.10.238

• 13C NMR, HRMS, as well as X-ray diffraction analysis (Figure 1, for details, see Supporting Information File 1). Based on this one-pot tandem electrophilic cyclization/[3 + 2] cycloaddition reactions, highly functionalized pyrazolo[5,1-a]isoquinolines can be obtained via palladium-catalyzed cross

Photochemical approach to functionalized benzobicyclo[3.2.1]octene structures via fused oxazoline derivatives from 4- and 5-(o-vinylstyryl)oxazoles

• Ivana Šagud,
• Simona Božić,
• Željko Marinić and
• Marija Šindler-Kulyk

Beilstein J. Org. Chem. 2014, 10, 2222–2229, doi:10.3762/bjoc.10.230

• ]. Various methodologies and new synthetic approaches for their preparation and reactivity have been reviewed [3]. Continuing our long-standing interest for photochemical intramolecular cycloaddition reactions of various β-heteroaryl-o-divinylbenzenes, furans [4][5][6], thiophenes [6][7][8], pyroles [9][10

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

Design and synthesis of multivalent neoglycoconjugates by click conjugations

• Feiqing Ding,
• Li Ji,
• Ronny William,
• Hua Chai and
• Xue-Wei Liu

Beilstein J. Org. Chem. 2014, 10, 1325–1332, doi:10.3762/bjoc.10.134

• has been established that the construction of well-defined multivalent, anomerically pure 3-amino-2,3-dideoxyneoglycoconjugate architectures was successfully achieved by using cycloaddition reactions of alkynes and azides. It is expected that this strategy will find extensive applications in

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

• 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

Thermodynamically stable [4 + 2] cycloadducts of lanthanum-encapsulated endohedral metallofullerenes

• Yuta Takano,
• Yuki Nagashima,
• M. Ángeles Herranz,
• Nazario Martín and
• Takeshi Akasaka

Beilstein J. Org. Chem. 2014, 10, 714–721, doi:10.3762/bjoc.10.65

• describe other EMFs [4][9][10]. Moreover, the only precedent of [4 + 2] cycloadducts of the fullerenes which have an open-shell electronic structure of the cage, e.g., La@C82, are thermodynamically unstable and show retro-cycloaddition reactions [10][11]. In addition, boat-to-boat inversion of the addend

• [5,6]-isomers, are allowed to be formed by cycloaddition reactions. (Please note that “site-isomer” refers to an isomer of the adducts which has the same fullerene and addend but different addition position – a classification proposed recently for fullerene’s chemistry by Martin et al. [14]). Therefore

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

• recent years, there have been many attempts to synthesize diversely modified pyrrolidines, both symmetric and asymmetric in nature. Several of these attempts involved 1,3-dipolar cycloaddition reactions involving azomethine ylides to give cycloadducts, which were further explored as potential antiviral

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

• (enamines and carbanions) or be involved in cycloaddition reactions affording tricyclic compounds by cascade processes. An unprecedented, co-catalyzed reaction involving enamines 51 as nucleophilic partners, also yields the H-pyrazolo[5,1-a]isoquinoline nucleus 48, in the presence of silver triflate and

• reaction involving nitriles 52 as pro-nucleophiles (Scheme 28) [71]. Wu and co-workers successfully employed the isoquinolinium-2-ylamides 43 as an ylidic species in two-component tandem [3 + 2]-cycloaddition reactions with a series of substrates including dimethyl acetylenedicarboxylate [72

• isoquinolinium-2-ylamide 43 undergoes a [3 + 2]-cycloaddition reaction with carbodiimide 54. Further intramolecular rearrangement yields the desired 1-(isoquinolin-1-yl)guanidine 55. Moreover, isoquinolinium-2-ylamides 43 can participate as 1,3-dipoles in [3 + 2]-cycloaddition reactions with in situ generated

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

• diazodicarbonyl compounds with arylsubstituted (aromatic) thioketones to establish their suitability for the preparation of 1,3-oxathioles and other sulfur-containing heterocycles [7][8]. The main goal of the present study was to investigate the scope and limitations of cycloaddition reactions of 2-diazo-1,3

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

• release the triazole product. Excursus: copper-catalyzed cycloaddition reactions of 1-haloalkynes and internal alkynes Mononuclear mechanistic proposals are also worth mentioning in the context of cycloaddition reactions of haloalkynes and internal alkynes with organoazides to give 1,4,5-trisubstituted

• , exchange of the halide group when 1-bromoalkynes are reacted with azides in the presence of copper(I) iodide [155] as observed by Rutjes et al. cannot be explained by this pathway. In 2006, the group of Nolan presented the synthesis of 1,4,5-trisubstituted-1,2,3-triazoles by cycloaddition reactions between

Diastereoselectivity in the Staudinger reaction of pentafluorosulfanylaldimines and ketimines

• Alexander Penger,
• Cortney N. von Hahmann,
• Alexander S. Filatov and
• John T. Welch

Beilstein J. Org. Chem. 2013, 9, 2675–2680, doi:10.3762/bjoc.9.303

• careful filtration of the desiccant, the dichloromethane solution of the imine was used in further reactions without purification or separation of unreacted amine or the enamine side product. Ketene imine cycloaddition reactions of α-SF5-substituted aldimines and ketimines Dropwise addition of the crude

A one-pot synthesis of 3-trifluoromethyl-2-isoxazolines from trifluoromethyl aldoxime

• Raoni S. B. Gonçalves,
• Michael Dos Santos,
• Guillaume Bernadat,
• Danièle Bonnet-Delpon and
• Benoit Crousse

Beilstein J. Org. Chem. 2013, 9, 2387–2394, doi:10.3762/bjoc.9.275

• unreactive towards trifluoroacetonitrile oxide 4. 1,3-Dipolar cycloaddition reactions have been studied from the theoretical standpoint since the 1970’s onwards [36][37] with an ever-increasing accuracy as computational methods evolved [38]. Assuming that the above-mentioned transformations occur via a

• partners (Figure 5) suggest that type-III cycloaddition reactions (where the dipole reacts via its LUMO and the dipolarophile via its HOMO) take place for every combination of reactants reported herein [45]. In this scenario, with the same dipole, the reactivity is expected to increase with the HOMO energy

Silica sulfuric acid: a reusable solid catalyst for one pot synthesis of densely substituted pyrrole-fused isocoumarins under solvent-free conditions

• Sudipta Pathak,
• Kamalesh Debnath and
• Animesh Pramanik

Beilstein J. Org. Chem. 2013, 9, 2344–2353, doi:10.3762/bjoc.9.269

• easily synthesized from silica gel and chlorosulfonic acid [26], was observed to improve the reactivity and selectivity in carbon–carbon bond-formation reactions [27][28], in cycloaddition reactions [29][30], in protection–deprotection reactions of multistep syntheses [31][32][33], in esterifications [34

Gold(I)-catalyzed enantioselective cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2013, 9, 2250–2264, doi:10.3762/bjoc.9.264

• area of cycloaddition reactions, which are of particular interest due to their potential for the rapid construction of optically active cyclic products. In this article we will summarize some of the most remarkable examples, emphasizing reaction mechanisms and key intermediates involved in the

• cyclizations [16]. Cycloaddition reactions are very important synthetic processes that allow the transformation of simple acyclic precursors into complex cyclic or polycyclic adducts in a rapid and efficient way [17][18], usually providing a rapid increase in skeletal and stereochemical complexity. Moreover

• cycloaddition processes in an enantioselective manner, so that the resulting cyclic products could be obtained in an optically pure fashion [27]. Herein, we describe the most relevant types of enantioselective cycloaddition reactions based on the use of carbophilic gold(I) complexes. We do not consider

Sequential Diels–Alder/[3,3]-sigmatropic rearrangement reactions of β-nitrostyrene with 3-methyl-1,3-pentadiene

• Peter A. Wade,
• Alma Pipic,
• Matthias Zeller and
• Panagiota Tsetsakos

Beilstein J. Org. Chem. 2013, 9, 2137–2146, doi:10.3762/bjoc.9.251

• been the subject of several theoretical investigations [7][8][9][10]. The necessary nitronic ester precursors are readily preparable by Lewis acid-promoted [4 + 2]-cycloaddition reactions of nitroalkenes with appropriate dienes, a general reaction first reported by Denmark and coworkers (Denmark Diels

• case of 1-(2-propenyl)cyclohexene only one of four possible regioisomers was observed [1]. However, it was not clear what the outcome would be for a simple open-chain conjugated diene. Consequently, cycloaddition reactions of 3-methyl-1,3-pentadiene were examined. This diene has both trisubstituted and

Gold catalysis for organic synthesis II

• F. Dean Toste

Beilstein J. Org. Chem. 2013, 9, 2040–2041, doi:10.3762/bjoc.9.241

• applications to the synthesis of complex natural products. The field has also witnessed growth through the discovery of other modes of reactivity. For example, gold-catalyzed cycloaddition reactions, examples of which are found in this Thematic Series, have featured prominently. Additionally, enantioselective

Gold-catalyzed cyclization of allenyl acetal derivatives

• Dhananjayan Vasu,
• Samir Kundlik Pawar and
• Rai-Shung Liu

Beilstein J. Org. Chem. 2013, 9, 1751–1756, doi:10.3762/bjoc.9.202

• of the acetate group at the allyl cation intermediate. Keywords: allenyl acetals; 5-alkylidenecyclopent-2-en-1-ones; cyclization; gold catalysis; Introduction Gold-catalyzed cyclization/cycloaddition reactions [1][2][3][4][5] are useful synthetic methods to construct complicated carbo- and