Synthesis of benzannelated sultams by intramolecular Pd-catalyzed arylation of tertiary sulfonamides

• Valentin A. Rassadin,
• Mirko Scholz,
• Anastasiia A. Klochkova,
• Armin de Meijere and
• Victor V. Sokolov

Beilstein J. Org. Chem. 2017, 13, 1932–1939, doi:10.3762/bjoc.13.187

• , sultams have been prepared employing Diels–Alder reactions, radical cyclizations, reductions of sulfonylimines, ring-closing metatheses, nucleophilic aromatic substitutions and Heck cyclizations [14][15][16]. Earlier on, our group has developed versatile syntheses of sultams based on the transformation of

Pd(OAc)₂/Ph₃P-catalyzed dimerization of isoprene and synthesis of monoterpenic heterocycles

• Dominik Kellner,
• Maximilian Weger,
• Andrea Gini and
• Olga García Mancheño

Beilstein J. Org. Chem. 2017, 13, 1807–1815, doi:10.3762/bjoc.13.175

• - and N-heterocycles The different dimers of isoprene can be transformed into a large number of derivatives such as terpene-alcohols or ethers [38]. Moreover, some isoprene dimers have been submitted to Diels–Alder reactions with olefins such as maleic acid anhydride or methacrolein to form products

• -12); MS (EI+) m/z: 166 [M+.] (1), 110 [C7H10O]+ (93), 97 [C6H9O]+ (100), 79 [C6H7]+ (19), 69 [C5H9]+ (26), 67 (16), 55 (19). Diels–Alder reactions General procedure: Dimer 2-TT (1.5 equiv) and the corresponding dienophile (1 equiv) were dissolved in toluene (0.5 M) and stirred for 4 hours at 150 °C

An eco-compatible strategy for the diversity-oriented synthesis of macrocycles exploiting carbohydrate-derived building blocks

• Sushil K. Maurya and
• Rohit Rana

Beilstein J. Org. Chem. 2017, 13, 1106–1118, doi:10.3762/bjoc.13.110

• the synthesis. The cyclization of the linear precursor is usually achieved by utilizing various ring-closing reactions such as Diels–Alder reactions, [15] aldol reactions, [16] copper-catalyzed azide–alkyne cycloaddition, [17][18] macrolactonization, macrolactamizations, Staudinger ligation or

Unpredictable cycloisomerization of 1,11-dien-6-ynes by a common cobalt catalyst

• Abdusalom A. Suleymanov,
• Dmitry V. Vasilyev,
• Valentin V. Novikov,
• Yulia V. Nelyubina and
• Dmitry S. Perekalin

Beilstein J. Org. Chem. 2017, 13, 639–643, doi:10.3762/bjoc.13.62

• formation of meta/para-products of Diels–Alder reactions [28][29][30][31][32], linear/branched products of hydrovinylation reactions [33][34], [2 + 2] cycloadditions vs Alder-ene reactions [35], E/Z isomerizations of alkenes [36][37] and other processes [38][39][40][41][42]. Herein, we report the

NMR reaction monitoring in flow synthesis

• M. Victoria Gomez and
• Antonio de la Hoz

Beilstein J. Org. Chem. 2017, 13, 285–300, doi:10.3762/bjoc.13.31

• to analyze NMR (via Labview software) data and optimize the reaction conditions. They performed a range of reactions including imine formation (Figure 14), electrophilic fluorinations and Diels–Alder reactions. This system was employed to perform kinetic studies, in-line structural characterization

• including DEPT spectra, 2D-NMR spectroscopy, 19F NMR spectroscopy and monitoring of the stereoselectivity in Diels–Alder reactions and self-optimization of flow conditions using a modified version of the Nelder–Mead algorithm. For the NMR integral data for each experiment, the algorithm (Figure 15) selects

Diels–Alder reactions of myrcene using intensified continuous-flow reactors

• Christian H. Hornung,
• Miguel Á. Álvarez-Diéguez,
• Thomas M. Kohl and
• John Tsanaktsidis

Beilstein J. Org. Chem. 2017, 13, 120–126, doi:10.3762/bjoc.13.15

• –Alder adduct of myrcene and acrylonitrile for the use as an odorant in the perfume industry [12]. A series of Diels–Alder reactions of myrcene (1) and another sesquiterpene, farnesene, with various dienophiles have been reported by Tabor et al. [13] for the use as solvents and surfactants. The emergence

• continuous flow [22][23]. Over the past years, Diels–Alder reactions of isoprene using laboratory-scale flow reactors were studied by different research groups [24][25]. A continuous-flow reactor can offer a range of benefits over batch processing, with the enhanced heat and mass transfer arguable being one

• . Results and Discussion The solution-phase Diels–Alder reactions presented herein follow the general reaction pathway shown in Scheme 1. The conjugated diene myrcene (1) was reacted with a series of dienophiles 2 to form the Diels–Alder adducts 3. Before investigating this reaction for continuous-flow

Diastereoselective anodic hetero- and homo-coupling of menthol-, 8-methylmenthol- and 8-phenylmenthol-2-alkylmalonates

• Matthias C. Letzel,
• Hans J. Schäfer and
• Roland Fröhlich

Beilstein J. Org. Chem. 2017, 13, 33–42, doi:10.3762/bjoc.13.5

• as a chiral auxiliary [27] to control the stereochemistry in Diels–Alder reactions [28], [2 + 2]- and [3 + 2]-cycloadditions and asymmetric ene reactions [29]; furthermore, it has been applied in 1,4-cuprate additions [30], Grignard additions [31], in supramolecular chemistry [32] and in alkylation

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

• Pavel Nagorny and
• Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

• catalysts for aza-Diels–Alder reactions of Danishefsky’s diene with imines (Scheme 5) [52]. A variety of ammonium salts (L7–L10) including chiral cinchonidine derivatives L7 and catalyst L10 were found to promote the reaction in low-to-good yields albeit with no enantioselectivity. Although it is perhaps

• isoquinolinium salts by Mancheno and co-workers [36][37][38][39]. Ammonium salt anion binding via C–H hydrogen bonds in solid state [40][41][42][43][44][45][50][51]. Early examples of ammonium salts being used for electrophilic activation of imines in aza-Diels–Alder reactions [52]. Ammonium salts as hydrogen

Development of a continuous process for α-thio-β-chloroacrylamide synthesis with enhanced control of a cascade transformation

• Olga C. Dennehy,
• Valérie M. Y. Cacheux,
• Benjamin J. Deadman,
• Denis Lynch,
• Stuart G. Collins,
• Humphrey A. Moynihan and
• Anita R. Maguire

Beilstein J. Org. Chem. 2016, 12, 2511–2522, doi:10.3762/bjoc.12.246

• compounds has been well documented [3]. The predominant site of reactivity is at the electrophilic β-carbon, which results from the combined influence of the amide and chloro substituents, mitigating the electron-donating effect of the sulfide moiety. Nucleophilic substitution [4], Diels–Alder reactions [5

Radical polymerization by a supramolecular catalyst: cyclodextrin with a RAFT reagent

• Kohei Koyanagi,
• Yoshinori Takashima,
• Takashi Nakamura,
• Hiroyasu Yamaguchi and
• Akira Harada

Beilstein J. Org. Chem. 2016, 12, 2495–2502, doi:10.3762/bjoc.12.244

• , including hydrolysis reactions [10][11][12][13][14][15], C–H bond activation [34][35][36], olefin epoxidation [37][38][39], Diels–Alder reactions [40][41][42], 1,3-dipole cycloadditions [43][44], and polymerizations [45][46][47], among others. Selective substrate recognition and activation are essential

Diels–Alder reactions in confined spaces: the influence of catalyst structure and the nature of active sites for the retro-Diels–Alder reaction

• Ángel Cantín,
• M. Victoria Gomez and
• Antonio de la Hoz

Beilstein J. Org. Chem. 2016, 12, 2181–2188, doi:10.3762/bjoc.12.208

• ] (see Figure 2a, b) that owing to the retro-DA reaction the selectivity of the endo-endo isomer decreases from 85% to 65% as we previously reported. [30] Considering the interesting application of beta zeolites as Lewis acid catalyst for Diels–Alder reactions in different fields, i.e., the formation of

Application of heterocyclic aldehydes as components in Ugi–Smiles couplings

• Katelynn M. Mason,
• Michael S. Meyers,
• Abbie M. Fox and
• Sarah B. Luesse

Beilstein J. Org. Chem. 2016, 12, 2032–2037, doi:10.3762/bjoc.12.191

• couplings in combination with post-condensation processes to efficiently increase structural complexity [8][9][10]. One of the most effective routes to polycyclic core structures uses intramolecular Diels–Alder reactions (IMDA) of tethered, substituted furans to provide stereoselective construction of

Stereo- and regioselectivity of the hetero-Diels–Alder reaction of nitroso derivatives with conjugated dienes

• Lucie Brulíková,
• Aidan Harrison,
• Marvin J. Miller and
• Jan Hlaváč

Beilstein J. Org. Chem. 2016, 12, 1949–1980, doi:10.3762/bjoc.12.184

• biologically active compounds. It is a variant of the Diels–Alder reaction where either the diene or the dienophile contains a heteroatom. Hetero-Diels–Alder reactions between conjugated dienes and nitroso dienophiles affording 1,2-oxazines are utilized for the synthesis of many biologically active molecules

• acylnitroso dienophile 5 was generated in the presence of thebaine (4) to selectively give the 1,2-oxazine 6 (Scheme 2). Several excellent reviews on nitroso hetero-Diels–Alder reactions have been published in the past, including general reviews on hetero-Diels–Alder reactions and their applications in

• organic synthesis [15][16][17][18][19][20][21][22][23][24], applications of nitroso hetero-Diels–Alder reactions for the synthesis of azasugars [10], and the utilization of nitroso hetero-Diels–Alder reactions in natural product synthesis [9][25] and the synthesis of bioactive molecules [26]. However

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