A chiral analog of the bicyclic guanidine TBD: synthesis, structure and Brønsted base catalysis

• Mariano Goldberg,
• Denis Sartakov,
• Jan W. Bats,
• Michael Bolte and
• Michael W. Göbel

Beilstein J. Org. Chem. 2016, 12, 1870–1876, doi:10.3762/bjoc.12.176

• of the guanidinium benzoate salt the six membered rings of 10 adopt conformations close to an envelope with the phenyl substituents in pseudo-axial positions. The unprotonated guanidine 10 catalyzes Diels–Alder reactions of anthrones and maleimides (25–30% ee). It also promotes as a strong Brønsted

• ][18][19] and used for highly enantioselective Strecker [17] and Diels–Alder reactions [19]. Compared to guanidine 7 ring expansion into structure 10 would shift the stereogenic phenyl groups into closer proximity to a hydrogen-bonded guest molecule and thereby might improve the enantioselective

Experimental and theoretical insights in the alkene–arene intramolecular π-stacking interaction

• Valeria Corne,
• Ariel M. Sarotti,
• Carmen Ramirez de Arellano,
• Rolando A. Spanevello and
• Alejandra G. Suárez

Beilstein J. Org. Chem. 2016, 12, 1616–1623, doi:10.3762/bjoc.12.158

• prepared from commercially available 9-anthracenyl methanol. When the Diels–Alder reactions were carried out in refluxing toluene, the desired ortho adducts 3a and 3b were obtained in good yields of 71% and 86%, respectively. However, the long reaction times (8–9 days) prompted us to evaluate these

• . Energy decomposition analysis (EDA) of the three complexes shown in Scheme 2. Thermal and Lewis acid promoted Diels–Alder reactions of 6a,b and cyclopentadiene. Supporting Information Supporting Information File 542: Experimental procedures, characterization and spectral data for synthesized compounds

Indenopyrans – synthesis and photoluminescence properties

• Andreea Petronela Diac,
• Ana-Maria Ţepeş,
• Albert Soran,
• Ion Grosu,
• Anamaria Terec,
• Jean Roncali and
• Elena Bogdan

Beilstein J. Org. Chem. 2016, 12, 825–834, doi:10.3762/bjoc.12.81

• dienophile component in inverse-electron demand Diels–Alder reactions, a series of new dihydroindeno[1,2-c]pyran derivatives was synthesized. Thus, the addition of freshly distilled indene as a diene component to oxadiazinones 1 as the dienophiles [29] under acidic conditions (TFA, TFAA) led to the formation

Regiodefined synthesis of brominated hydroxyanthraquinones related to proisocrinins

• Joyeeta Roy,
• Tanushree Mal,
• Supriti Jana and
• Dipakranjan Mal

Beilstein J. Org. Chem. 2016, 12, 531–536, doi:10.3762/bjoc.12.52

• , and show promising antifeedant properties [16]. A brief literature survey revealed that the routes for the synthesis of anthraquinones are primarily based upon five categories, such as Friedel–Crafts reactions, Hauser annulations, Diels–Alder reactions, transition metal-mediated reactions and

The aminoindanol core as a key scaffold in bifunctional organocatalysts

• Isaac G. Sonsona,
• Eugenia Marqués-López and
• Raquel P. Herrera

Beilstein J. Org. Chem. 2016, 12, 505–523, doi:10.3762/bjoc.12.50

• acting through hydrogen bonding, such as thiourea, urea, squaramide, and thioamide frameworks. These have been efficiently employed in a few organocatalytic processes such as Friedel–Crafts alkylations, Michael additions, Diels–Alder reactions and aza-Henry reactions, as discussed below. Friedel–Crafts

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• activation. Asymmetric synthesis of nitrobicyclo[3.2.1]octan-2-one derivatives [26]. Asymmetric tandem Michael–Henry reaction catalyzed by 50 [27]. Asymmetric Diels–Alder reactions of 3-vinylindoles 51 [29]. Proposed transition state and activation mode of the asymmetric Diels–Alder reactions of 3

Self and directed assembly: people and molecules

• Tony D. James

Beilstein J. Org. Chem. 2016, 12, 391–405, doi:10.3762/bjoc.12.42

• catalyst of diastereoselective aza-Diels–Alder reactions [68] (Figure 14). While, the structure of the “chiral boron reagent” still remains unknown during our investigation of analogues we discovered a very interesting three-component self-assembly. Chiral binol, a chiral amine and 2-formylbenzeneboronic

• in 2002. (Left) Private photo taken in Osaka. (Right) Photo taken in Tokyo by Katsuhiko Ariga. Preparation of chiral boron reagent and use as catalyst for aza-Diels–Alder reactions. Chiral three component self-assembling system. Reaction of trimethylsilyl cyanide with tricarbonyl (η5-cyclohexadienyl

A journey in bioinspired supramolecular chemistry: from molecular tweezers to small molecules that target myotonic dystrophy

• Steven C. Zimmerman

Beilstein J. Org. Chem. 2016, 12, 125–138, doi:10.3762/bjoc.12.14

• related class of achiral molecular tweezers was developed by Klärner et al., with their first report appearing in 1996 [32]. These di-, tri-, and tetramethylene-bridged aromatic systems (e.g., 19 and 20) were prepared by consecutive Diels–Alder reactions and have been shown to exhibit a remarkably rich

Iron complexes of tetramine ligands catalyse allylic hydroxyamination via a nitroso–ene mechanism

• David Porter,
• Belinda M.-L. Poon and
• Peter J. Rutledge

Beilstein J. Org. Chem. 2015, 11, 2549–2556, doi:10.3762/bjoc.11.275

• regioisomers in the hetero-Diels–Alder reaction with nitroso compounds, yet Cenini et al. only detected one isomer. From this observation they concluded that their Ru-catalysed amination reaction and the Diels–Alder reactions were occurring ‘on metal’ without generation of a free nitroso species [57]. In

Synthesis of constrained analogues of tryptophan

• Elisabetta Rossi,
• Valentina Pirovano,
• Marco Negrato,
• Giorgio Abbiati and
• Monica Dell’Acqua

Beilstein J. Org. Chem. 2015, 11, 1997–2006, doi:10.3762/bjoc.11.216

• -3-carboxylic acid derivatives 3, constrained analogues of tryptophan, could be synthesized by Diels–Alder reactions between 2-vinylindoles 1 [22] as dienes and methyl 2-acetamidoacrylate (dehydroalanine) 2 [23] as dienophile (Scheme 1). Reported [4 + 2] cycloaddition reactions of methyl 2

• ascribed the observed reactivity to the formation of a complex between EtAlCl2 and 2, verified via 1H NMR experiments, and involving coordination with both amide and ester carbonyl groups [29]. Conceivably, the same activated complex participated in our Diels–Alder reactions, see footnote a in Table 1

• and 4). It is well known that reaction rates and selectivity in Diels–Alder reactions are affected by solvents [30][31][32]. In particular, polarity and hydrogen bond donor ability of the solvent can impact the diastereoisomeric ratios in a Diels–Alder reaction. Such an effect seems negligible in the

Tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR). An easy entry to linear bicyclic scaffolds

• Javier Miró,
• María Sánchez-Roselló,
• Álvaro Sanz,
• Fernando Rabasa,
• Carlos del Pozo and
• Santos Fustero

Beilstein J. Org. Chem. 2015, 11, 1486–1493, doi:10.3762/bjoc.11.161

• -bonding catalysts for Diels–Alder reactions [28]. However, in our case no influence was observed when the reaction was performed in the presence of diaryl thioureas (Table 1, entry 13). Finally, the use of benzoquinone (BQ) as an additive, which has been reported to suppress the formation of byproducts in

The chemical behavior of terminally tert-butylated polyolefins

• Dagmar Klein,
• Henning Hopf,
• Peter G. Jones,
• Ina Dix and
• Ralf Hänel

Beilstein J. Org. Chem. 2015, 11, 1246–1258, doi:10.3762/bjoc.11.139

• . Exploratory photochemical studies were carried out with tetraene 19 as the model compound. On irradiation this reacted with oxygen to the stable endo-peroxide 52. Keywords: bromination; Diels–Alder reactions; epoxidation; photochemistry; polyolefins; reactivity; hydrogenation; Introduction Several years ago

• indications that DMDO oxidizes “inner” double bonds preferentially. In principle, heterocycles with larger rings could also be produced in these experiments; however, at present we have no experimental evidence for these alternative routes. Diels–Alder reactions Since we expected steric hindrance effects to

• reacted with, e.g., heptaene 22 up to 75 °C. In summary, the tert-butyl protected oligoenes participate in Diels−Alder reactions, as diene components with up to nine consecutive double bonds, with very reactive dienophiles (PTAD, TCNE). Only in the most extended cases are 2:1 adducts produced, and in all

Multivalent polyglycerol supported imidazolidin-4-one organocatalysts for enantioselective Friedel–Crafts alkylations

• Tommaso Pecchioli,
• Manoj Kumar Muthyala,
• Rainer Haag and
• Mathias Christmann

Beilstein J. Org. Chem. 2015, 11, 730–738, doi:10.3762/bjoc.11.83

• properties. Hyperbranched polymers like polytriallylsilane or polyglycerol have been used in a wide range of transformations including aldol condensations [22], Suzuki cross-couplings [23] and Diels–Alder reactions [24], to name a few, with metal complexes as catalytically active principle. The advent of

• support in asymmetric organocatalysis. The use of chiral imidazolidinones in organocatalysis has been extensively reported for a wide range of enantioselective reactions involving α,β-unsaturated aldehydes, such as the Diels–Alder reactions [50], 1,3-dipolar cycloadditions [51] and Friedel–Crafts

• alkylations [52][53]. To date, heterogenizations have been applied mainly in Diels–Alder reactions [54][55][56][57][58][59][60][61]. Nevertheless, Friedel–Crafts alkylations are recently emerging as a compelling field of study as reported by Pericàs [62] and others [58][60]. The simple approach providing an

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

• sulfones. Keywords: dimethyl acetylenedicarboxylate (DMAD); hetero-Diels–Alder reactions; high pressure reactions; methyl propiolate; thioketones; thiopyrans; Introduction A series of recent publications evidence that, in contrast to earlier opinions, thioketones are useful building blocks for the

• Discussion Under standard conditions (benzene, rt), the reaction of 1a with 2a is slow, and it requires several days to be complete [9]. For that reason, we modified the procedure by using THF as a solvent and LiClO4 as a known, efficient catalyst applied frequently in diverse Diels–Alder reactions [17

• of the products were determined based on the spectroscopic data. Thus, similar to hetero-Diels–Alder reactions with maleic anhydride [14], the C=C bond of the thiophene ring of 1h is part of the reactive heterodiene system. The reactions of 2b with thiobenzosuberone 1b and thiobenzosuberenone 1c were

Chemoselective O-acylation of hydroxyamino acids and amino alcohols under acidic reaction conditions: History, scope and applications

• Tor E. Kristensen

Beilstein J. Org. Chem. 2015, 11, 446–468, doi:10.3762/bjoc.11.51

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

• ); C4–P3–C3 100.1(2); C4–P3–P4 95.44(17); C3–P3–P4 101.35(17); C6–P4–C45 101.6(3);C6–P4–P3 93.40(18); C45–P4–P3 100.8(2). Synthesis of 1-alkyl-1,2-diphospholes 1a–e. The cycloaddition reactions of 1-alkyl-1,2-diphospholes 1a–e. The retro-Diels–Alder reactions of the cycloadducts 2a–с, and 2e. 31Р {1H

Organic chemistry on surfaces: Direct cyclopropanation by dihalocarbene addition to vinyl terminated self-assembled monolayers (SAMs)

• Malgorzata Adamkiewicz,
• David O’Hagan and
• Georg Hähner

Beilstein J. Org. Chem. 2014, 10, 2897–2902, doi:10.3762/bjoc.10.307

• including azide–alkyne cycloadditions [9][10], Diels–Alder reactions [11][12], maleimide–thiol reactions [13], thiol–ene additions [14], and imine/oxime conjugations [15]. In this article we demonstrate that dihalocarbenes can be used to generate dihalocyclopropanes on olefin terminated SAMs. We recently

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

• Würzburg, Germany 10.3762/bjoc.10.288 Abstract Nanodiamonds functionalized with different organic moieties carrying terminal amino groups have been synthesized. These include conjugates generated by Diels–Alder reactions of ortho-quinodimethanes formed in situ from pyrazine and 5,6-dihydrocyclobuta[d

• ortho-quinodimethanes. These can be used as dienes in Diels–Alder reactions with π-bonds on the surface of nanodiamond. The use of pyrazine 3 results in a significantly increased grafting rate compared to other aromatic moieties linked by carbon–carbon bonds. Furthermore, a modified Kaiser test for the

Expanding the scope of cyclopropene reporters for the detection of metabolically engineered glycoproteins by Diels–Alder reactions

• Anne-Katrin Späte,
• Verena F. Schart,
• Julia Häfner,
• Andrea Niederwieser,
• Thomas U. Mayer and
• Valentin Wittmann

Beilstein J. Org. Chem. 2014, 10, 2235–2242, doi:10.3762/bjoc.10.232

• higher fluorescence staining of cell-surface glycoconjugates, the glucosamine derivative gave higher labeling efficiency with protein preparations containing also intracellular proteins. Keywords: bioorthogonal chemistry; carbohydrates; cyclopropenes; inverse-electron-demand Diels-Alder reactions

Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

• ] cycloadducts, 3-spirocyclohexene-2-oxindoles, in high yields with excellent ee and dr. These asymmetric [4 + 2] annulations of allenoates with activated alkenes significantly offset the limitations of Diels–Alder reactions when synthesizing enantioenriched multisubstituted cyclohexenes. At about the same time

• groups, could undergo further transformations, such as Diels–Alder reactions, reduction, and hydrolysis, to afford nitrogen-containing heterocyclic compounds. In contrast to the intermolecular aza-RC reaction/Michael addition sequence described above, the mechanism was assumed to involve an initial aza

A new charge-tagged proline-based organocatalyst for mechanistic studies using electrospray mass spectrometry

• J. Alexander Willms,
• Rita Beel,
• Martin L. Schmidt,
• Christian Mundt and
• Marianne Engeser

Beilstein J. Org. Chem. 2014, 10, 2027–2037, doi:10.3762/bjoc.10.211

• [8][10][11][12][13][14][15][16][17] to purely organic Diels–Alder reactions [18][19] to cite only a few representative examples. However, the detection of transient reactive species is often hindered by their very low concentration. A reacting solution of a catalytic transformation typically contains

Aza-Diels–Alder reaction between N-aryl-1-oxo-1H-isoindolium ions and tert-enamides: Steric effects on reaction outcome

• Amitabh Jha,
• Ting-Yi Chou,
• Zainab ALJaroudi,
• Bobby D. Ellis and
• T. Stanley Cameron

Beilstein J. Org. Chem. 2014, 10, 848–857, doi:10.3762/bjoc.10.81

• -isoindolinones as the N-acyliminium ion source and performing [4 + 2] imino-Diels–Alder reactions with tert-enamides. Our literature search also infuses confidence in the proposed scheme because the synthesis of N-aryl-3-hydroxyisoindolinones is well studied and standardized [13][14][15] and the reactions

• analogous to the final step of imino [4 + 2] Diels–Alder reactions between N-acyliminium ions and electron-rich dienophiles are reported [13][14][15]. We synthesized eight N-aryl-3-hydroxyisoindolinones from substituted anilines and phthalic anhydride following the reported procedure [13]. Previously

• reported reaction conditions for imino [4 + 2] Diels–Alder reactions [13][14] were employed here for the electrocyclization of N-acyliminium ions from N-aryl-3-hydroxyisoindolinones and tert-enamide analogues namely N-vinylpyrrolidone and N-vinylcaprolactam as the electron-rich dienophiles. Sixteen

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

• outcome and forced us to explore new catalytic systems. While searching for this goal, we were attracted by the possible application of copper-catalysis, which has always been an effective tool especially with Diels–Alder reactions [26][27]. Thus, we studied the effect of a number of catalytic systems and

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

Synthesis of 3,4-dihydro-1,8-naphthyridin-2(1H)-ones via microwave-activated inverse electron-demand Diels–Alder reactions

• Salah Fadel,
• Youssef Hajbi,
• Mostafa Khouili,
• Said Lazar,
• Franck Suzenet and
• Gérald Guillaumet

Beilstein J. Org. Chem. 2014, 10, 282–286, doi:10.3762/bjoc.10.24

• -demand Diels–Alder reaction under microwave irradiation [22][23][24]. The use of 1,2,4-triazines in inverse electron-demand Diels–Alder reactions proved to be an efficient strategy for the construction of various heterocyclic compounds [25][26][27], such as azacarbazoles [28][29][30][31][32][33

• ynamides 2–5 [22][23][24][53] afforded triazinylpent-4-ynamides 6–9 in moderate to good yields (Scheme 3, Table 2). Intramolecular inverse electron-demand Diels–Alder reactions With the tethered triazines 6–9 in hand, we were able to study the cycloaddition reaction under microwave heating following the

• yields. The results are given in Table 5. Conclusion In this article, we report the successful application of a new synthesis strategy leading to 1-substituted 3,4-dihydro-1,8-naphthyridin-2(1H)-ones by inverse electron-demand Diels–Alder reactions under microwave activation. We also synthesized 5