Catalytic asymmetric oxo-Diels–Alder reactions with chiral atropisomeric biphenyl diols

• Chi-Tung Yeung,
• Wesley Ting Kwok Chan,
• Wai-Sum Lo,
• Ga-Lai Law and
• Wing-Tak Wong

Beilstein J. Org. Chem. 2019, 15, 955–962, doi:10.3762/bjoc.15.92

• formation of a supramolecular structure whereas that of 6, containing additional CF3 substituents, shows the formation of a monomeric structure. Diols 1–6 were found to be active organocatalysts in oxo-Diels–Alder reactions in which 2 recorded a 72% ee with trimethylacetaldehyde as a substrate. Keywords

Coordination chemistry and photoswitching of dinuclear macrocyclic cadmium-, nickel-, and zinc complexes containing azobenzene carboxylato co-ligands

• Jennifer Klose,
• Tobias Severin,
• Peter Hahn,
• Alexander Jeremies,
• Jens Bergmann,
• Daniel Fuhrmann,
• Jan Griebel,
• Bernd Abel and
• Berthold Kersting

Beilstein J. Org. Chem. 2019, 15, 840–851, doi:10.3762/bjoc.15.81

• drastically alter its structural properties and reactivities. Prominent examples are the cis-bromination of α,β-unsaturated carboxylato ligands [2], regioselective Diels–Alder reactions of encapsulated dienoate ligands [3], and the stabilization of unusual co-ligand conformations, respectively [4]. The

Mechanistic studies of an L-proline-catalyzed pyridazine formation involving a Diels–Alder reaction with inverse electron demand

• Anne Schnell,
• J. Alexander Willms,
• S. Nozinovic and
• Marianne Engeser

Beilstein J. Org. Chem. 2019, 15, 30–43, doi:10.3762/bjoc.15.3

• intermediates [4][5][6]. Various types of reactions have been studied successfully by ESIMS ranging from Ziegler–Natta polymerization [7] and coupling reactions [8][9] to organic reactions such as the Baylis–Hillman [10][11][12][13][14][15], aldol [16][17][18] or Diels–Alder reactions [19][20]. An advantageous

• ][43][44][45][46][47]. Tetrazines and their reactivity in Diels–Alder reactions with inverse electron demand are of interest in the field of biology [48][49]. Very recently, they have been studied by mass spectrometric means [50]. In 2008, Xie et al. [51] published an L-proline-catalyzed reaction

First thia-Diels–Alder reactions of thiochalcones with 1,4-quinones

• Grzegorz Mlostoń,
• Katarzyna Urbaniak,
• Paweł Urbaniak,
• Anna Marko,
• Anthony Linden and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2018, 14, 1834–1839, doi:10.3762/bjoc.14.156

• cycloadduct was isolated in 37% yield. Keywords: hetero-Diels–Alder reactions; quinone dyes; quinones; sulfur heterocycles; thiochalcones; Introduction Hetero-Diels–Alder reactions are considered to be a powerful methodology widely explored for the synthesis of six-membered heterocycles [1][2] with numerous

• applications for the construction of complex molecules including naturally occurring products [3][4], drugs [5][6], agrochemicals [7], etc. In addition, asymmetric hetero-Diels–Alder reactions are of current interest [8][9][10]. Whereas aza- and oxa-Diels–Alder reactions are frequently applied, thia-Diels

• cycloaddition reactions not only as heterodienes [17][18][19], but also as heterodipolarophiles [15]. In two recent publications we reported new thia-Diels–Alder reactions of aryl, hetaryl and ferrocenyl-substituted thiochalcones with acetylenic dienophiles, which lead to the corresponding 4H-thiopyrans in a

Recent applications of chiral calixarenes in asymmetric catalysis

• Mustafa Durmaz,
• Erkan Halay and
• Selahattin Bozkurt

Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117

• . Chiral AlIII–calixarene complexes bearing distally positioned chiral substituents. Asymmetric MPV reduction in the presence of chiral calix[4]arene diphosphites. Synthesis of enantiomerically pure inherently chiral calix[4]arene phosphonic acid. Asymmetric aza-Diels–Alder reactions catalyzed by (cR,pR

Stepwise radical cation Diels–Alder reaction via multiple pathways

• Ryo Shimizu,
• Yohei Okada and
• Kazuhiro Chiba

Beilstein J. Org. Chem. 2018, 14, 704–708, doi:10.3762/bjoc.14.59

• course of our study, we discovered that radical cation Diels–Alder reactions are also possible by electrocatalysis, however, the scope was limited to styrenes [34]. Described herein is a stepwise radical cation Diels–Alder reaction of enol ethers by electrocatalysis, which proceeds via multiple unique

• also effective for the aryl vinyl ether. While the mechanism is still controversial, most reported radical cation Diels–Alder reactions are highly stereoselective, even including stereospecific concerted examples. On the other hand, our current results clearly indicate that a stepwise mechanism is also

• development in our laboratory. GC–MS Monitoring of the oxidative SET-triggered reaction of aryl vinyl ether 1c. Radical cation Diels–Alder reaction of trans-anethole [17]. Radical cation Diels–Alder reactions of aryl vinyl ether and sulfides [17][25]. Radical cation Diels–Alder reaction of aryl vinyl ether (1

An air-stable bisboron complex: a practical bidentate Lewis acid catalyst

• Longcheng Hong,
• Sebastian Ahles,
• Andreas H. Heindl,
• Gastelle Tiétcha,
• Andrey Petrov,
• Zhenpin Lu,
• Christian Logemann and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2018, 14, 618–625, doi:10.3762/bjoc.14.48

• reactions combining the IEDDA step with rearrangements [15] or additional Diels–Alder reactions [16]. However, the methodology requires an air and moisture-sensitive bisboron catalyst. The preparation as well as the handling requires special equipment such as a glovebox, therefore, restricting its

Syn-selective silicon Mukaiyama-type aldol reactions of (pentafluoro-λ⁶-sulfanyl)acetic acid esters with aldehydes

• Anna-Lena Dreier,
• Andrej V. Matsnev,
• Joseph S. Thrasher and
• Günter Haufe

Beilstein J. Org. Chem. 2018, 14, 373–380, doi:10.3762/bjoc.14.25

• [22]. There are not many transformations of aliphatic SF5 compounds described in the literature. Among them are the preparation and derivatization of SF5-aldehydes [23], Diels–Alder reactions [24][25][26], the “click reaction” of SF5-acetylenes with azides to form triazoles [27], and 1,3-dipolar

Synthetic mRNA capping

• Fabian Muttach,
• Nils Muthmann and
• Andrea Rentmeister

Beilstein J. Org. Chem. 2017, 13, 2819–2832, doi:10.3762/bjoc.13.274

• structure of Ecm1 which forms a substrate binding cleft rather than a pocket [94]. Vinylbenzyl-modified cap analogues (bearing the modification at either the N7 or N2-position) provided a platform for inverse electron-demand Diels–Alder reactions with tetrazine conjugates and for photo-click reactions using

Preparation and isolation of isobenzofuran

• Morten K. Peters and
• Rainer Herges

Beilstein J. Org. Chem. 2017, 13, 2659–2662, doi:10.3762/bjoc.13.263

• laboratory scale with high yields, from affordable, commercially available starting materials. Keywords: [4 + 2] cycloaddition; Diels–Alder; isobenzofuran; trapping reagent; Introduction Isobenzofurans have been described as the most reactive dienes for Diels–Alder reactions [1][2][3][4][5]. Their high

• reactivity is mainly due to the resonance energy gained by formation of a benzene ring in the cycloaddition product (Scheme 1) [6]. Isobenzofurans have been extensively used as 4 electron (diene) components in Diels–Alder reactions, and moreover in other cycloaddition reactions such as [4 + 3], [4 + 4], [8

• (mp 20 °C) with a yield of 66%. The solid compound can be stored for up to 8 months at −15 °C without decomposition (polymerization). Conclusion Isobenzofuran (1) is one of the most reactive dienes in Diels–Alder reactions and other cycloadditions. For practical applications it has been generated and

Asymmetric synthesis of propargylamines as amino acid surrogates in peptidomimetics

• Matthias Wünsch,
• David Schröder,
• Tanja Fröhr,
• Lisa Teichmann,
• Sebastian Hedwig,
• Nils Janson,
• Clara Belu,
• Jasmin Simon,
• Shari Heidemeyer,
• Philipp Holtkamp,
• Jens Rudlof,
• Lennard Klemme,
• Alessa Hinzmann,
• Beate Neumann,
• Hans-Georg Stammler and
• Norbert Sewald

Beilstein J. Org. Chem. 2017, 13, 2428–2441, doi:10.3762/bjoc.13.240

• cycloaddition, CuAAC and RuAAC), the thiol–yne reaction, Diels–Alder reactions and the Sonogashira cross-coupling. While amino acids with a terminal alkyne in the side chain are well-known, the synthesis of their correlates where the carboxy group is replaced by a terminal alkyne is still tedious. Nevertheless

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

• Grzegorz Mlostoń and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221

• changes to non-concerted stepwise processes, which can involve zwitterionic or diradical intermediates. [4 + 2]-Cycloadditions (Diels–Alder reactions) In analogy to reactions with tetracyanoethene (TCNE), the first [4 + 2]-cycloadditions (Diels–Alder reactions) of E-1a were performed using typical 1,3

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