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

• atoms covalently bonded to a benzylic carbon (Scheme 8). In 2016 Maruoka and Shirakawa followed up the aforementioned studies by demonstrating that tetraalkylammonium salts L5, L6, L11 and L12 as well as TBAI could activate imines toward aza-Diels–Alder reaction with Danishefsky’s diene (Scheme 9) [51

• coordinating TfO− anion did not accelerate the cycloaddition. In 2015, Takeda, Minakata and co-workers demonstrated that 2-iodoimidazolium salt L24 could serve as an efficient catalyst of the aza-Diels−Alder reaction of aldimines and Danishefsky diene (Scheme 19) [90]. Other organohalides such as

Synthesis of polyhydroxylated decalins via two consecutive one-pot reactions: 1,4-addition/aldol reaction followed by RCM/syn-dihydroxylation

• Michał Malik and
• Sławomir Jarosz

Beilstein J. Org. Chem. 2016, 12, 2602–2608, doi:10.3762/bjoc.12.255

• -decalins and trans-hydrindanes (Scheme 1) [22][23][24][25]. It relies on the use of sugar-derived allyltin (such as 5) followed by ZnCl2-induced fragmentation into dienoaldehyde 6, subsequent Horner–Wadsworth–Emmons olefination, and intramolecular Diels–Alder reaction. In this paper, we explore the

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

A new paradigm for designing ring construction strategies for green organic synthesis: implications for the discovery of multicomponent reactions to build molecules containing a single ring

• John Andraos

Beilstein J. Org. Chem. 2016, 12, 2420–2442, doi:10.3762/bjoc.12.236

• ], or malonate diesters via Claisen condensations followed by hydrolysis and decarboxylation. The greenest routes appear in the [4 + 2] strategy. The three-step route beginning with photochemical ring opening of cyclobutenone to give vinylketene, followed by Diels–Alder addition to ethylene leading to

• cyclohexenone, followed by hydrogenation is 100% atom economical yielding no byproducts. The next best route with an 86% atom economy is the Diels–Alder addition of ketene, generated by pyrolysis of acetone, to 1,3-butadiene to give cyclohex-3-enone, which upon hydrogenation yields cyclohexanone. The only

Methylenelactide: vinyl polymerization and spatial reactivity effects

• Judita Britner and
• Helmut Ritter

Beilstein J. Org. Chem. 2016, 12, 2378–2389, doi:10.3762/bjoc.12.232

• donating (“pushing”) oxygen atom. Monomers with such substitution patterns are defined as captodative or push–pull monomers [1]. MLA was first synthesized in 1969 by Scheibelhoffer et al. through a bromination of L-lactide followed by a basic HBr elimination [2]. In 2008, the first Diels–Alder reaction

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

• Científica Aplicada (IRICA), Avda. Camilo José Cela s/n, E-13071-Ciudad Real, Spain 10.3762/bjoc.12.208 Abstract Diels–Alder cycloaddition between cyclopentadiene and p-benzoquinone has been studied in the confined space of a pure silica zeolite Beta and the impact on reaction rate due to the concentration

• effect within the pore and diffusion limitations are discussed. Introduction of Lewis or Brønsted acid sites on the walls of the zeolite strongly increases the reaction rate. However, contrary to what occurs with mesoporous molecular sieves (MCM-41), Beta zeolite does not catalyse the retro-Diels–Alder

• reaction, resulting in a highly selective catalyst for the cycloaddition reaction. Keywords: catalysis; Diels–Alder; retro-Diels–Alder; zeolites; Introduction The Diels–Alder reaction (DAR) is one of the most useful reactions in organic synthesis. In order to improve the yield and to avoid the

The direct oxidative diene cyclization and related reactions in natural product synthesis

• Juliane Adrian,
• Leona J. Gross and
• Christian B. W. Stark

Beilstein J. Org. Chem. 2016, 12, 2104–2123, doi:10.3762/bjoc.12.200

• obtained via an intramolecular Diels–Alder reaction, epoxidation and protection (Scheme 22) [170]. Conclusion The direct oxidative cyclization of 1,5-dienes is known for more than 90 years, since the early finding by Kötz and Steche in 1924. While mechanistic and stereochemical aspects were in the center

Diastereoselective synthesis of 3,4-dihydro-2H-pyran-4-carboxamides through an unusual regiospecific quasi-hydrolysis of a cyano group

• Mikhail Yu. Ievlev,
• Oleg V. Ershov,
• Mikhail Yu. Belikov,
• Angelina G. Milovidova,
• Viktor A. Tafeenko and
• Oleg E. Nasakin

Beilstein J. Org. Chem. 2016, 12, 2093–2098, doi:10.3762/bjoc.12.198

• been recently described is the involvement of diazolactones in an inverse electron-demand Diels–Alder reaction [13]. At the same time the synthesis of 3,4-dihydro-2H-pyrans with a carboxamide group is a not sufficiently explored area. There is only one way to produce 3,4-dihydro-2H-pyran-4-carboxamides

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

• components. In the presence of these heterocyclic aldehydes, reactions tolerated variations in amine components and led to either isolated N-arylamide Ugi–Smiles adducts or N-arylepoxyisoindolines, products of tandem Ugi–Smiles Diels–Alder cyclizations, in moderate yields. A thienyl-substituted aldehyde was

• also a competent component for Ugi–Smiles adduct formation. Keywords: Diels–Alder cycloaddition; epoxyisoindoline; multicomponent coupling reaction; tandem reaction; Ugi–Smiles coupling; Introduction Synthetic methods to efficiently prepare libraries of biologically-relevant compounds are in demand

• 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

• , Czech Republic Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA 10.3762/bjoc.12.184 Abstract The hetero-Diels–Alder reaction between a nitroso dienophile and a conjugated diene to give the 3,6-dihydro-2H-1,2-oxazine scaffold is useful for the synthesis of

• stereo- and regioselectivity for the synthesis of 1,2-oxazine scaffolds. Keywords: diene; hetero-Diels–Alder; nitroso compounds; regioselectivity; stereoselectivity; Review Introduction The hetero-Diels–Alder reaction represents one of the most important methods in organic synthesis, providing various

• 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

Bridgehead vicinal diallylation of norbornene derivatives and extension to propellane derivatives via ring-closing metathesis

• Sambasivarao Kotha and
• Rama Gunta

Beilstein J. Org. Chem. 2016, 12, 1877–1883, doi:10.3762/bjoc.12.177

• as strained as cyclopropane or cyclobutane (norbornene, 100 kJ/mol; cyclopropane, 115 kJ/mol; cyclobutane, 110 kJ/mol) [4][5]. Some of the annulated norbornene derivatives undergo retro Diels–Alder (rDA) reactions at ambient temperature in the presence of methylaluminium dichloride and a reactive

• ring-closing metathesis (RCM) [24][25][26][27][28][29][30][31][32]. Whereas, the diallyl derivative 2 can be derived from a readily available Diels–Alder (DA) adduct 3 through an allylation sequence. Results and Discussion Installation of two C–C bonds to generate quaternary centers in a

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

• ]. Depending on the substituents and the strength of the Brønsted base either Diels–Alder adducts or Michael products may be formed. Weaker bases such as ion-free bisoxazolines [28] or triethylamine are known to induce Diels–Alder adducts selectively whereas strongly basic guanidines such as 8 may also form

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

• reported the synthesis of a novel chiral auxiliary that demonstrated to be very efficient in an asymmetric Diels–Alder reaction between the acrylic ester derivative and cyclopentadiene [16]. The facial selectivity of this reaction proved to be due to an aryl–vinyl π-stacking intramolecular interaction that

• 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

• room temperature, account for this explanation. With the aim to determine if the strength of the intramolecular π-stacking interaction can have any influence in the inductive capacity, we studied the Diels–Alder reaction of acrylates 6a,b with cyclopentadiene (Table 2). All cycloadditions were endo

The EIMS fragmentation mechanisms of the sesquiterpenes corvol ethers A and B, epi-cubebol and isodauc-8-en-11-ol

• Patrick Rabe and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2016, 12, 1380–1394, doi:10.3762/bjoc.12.132

• ions produced via retro-Diels–Alder reaction [5][6]. Such diagnostic fragment ions are of high value to delineate structural proposals for unknown analytes from their mass spectra, but for unambiguous proof of the suggested structures a synthesis of reference material is essential. Back in the 1960s

Artificial Diels–Alderase based on the transmembrane protein FhuA

• Hassan Osseili,
• Daniel F. Sauer,
• Klaus Beckerle,
• Marcus Arlt,
• Tomoki Himiyama,
• Tino Polen,
• Akira Onoda,
• Ulrich Schwaneberg,
• Takashi Hayashi and
• Jun Okuda

Beilstein J. Org. Chem. 2016, 12, 1314–1321, doi:10.3762/bjoc.12.124

• . Copper(II) was attached by coordination to a terpyridyl ligand. The spacer length was varied in the back of the ligand framework. These biohybrid catalysts were shown to be active in the Diels–Alder reaction of a chalcone derivative with cyclopentadiene to preferentially give the endo product. Keywords

• reported. The Diels–Alder reaction is a powerful C–C bond formation reaction, widely used in organic chemistry, e.g., for the synthesis of natural products [28]. This reaction is known to be catalyzed by Lewis acids such as a Cu(II) complex [29]. Additionally, structurally defined catalysts are found to

• = 6301 Da). The signal of m/z = 6111 Da results from saponification of the ester and the maleimide moiety (calcd (M + H2O + Na+): m/z = 6111 Da, found: m/z = 6111 Da). We were unable to detect the copper ion in the MALDI–TOF–MS. The isolated biohybrid catalysts were tested in the Diels–Alder reaction of

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

• Mohammad Haji

Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121

• phosphorylated heterocycles is the condensation of an activated methylene component with a carbonyl compound followed by subsequent transformations such as intramolecular cyclization, Michael-type addition and hetero-Diels–Alder cycloaddition. 3.1 Domino Knoevenagel/phospha-Michael process A convenient one-pot

• conditions are summarized in Table 1. 3.2 Domino Knoevenagel/hetero-Diels–Alder process The one-pot synthesis of dihydropyrans via a three-component reaction between an activated methylene compound, an aldehyde and an electron-rich alkene was firstly reported by Tietze et al. [72]. Collignon et al. applied

• )phosphonates. Synthesis of phosphonodihydropyrans via a domino Knoevenagel/hetero-Diels–Alder process. Multicomponent synthesis of phosphonodihydrothiopyrans via a domino Knoevenagel/hetero-Diels–Alder process. One-pot four-component synthesis of 1,2-dihydroisoquinolin-1-ylphosphonates under multicatalytic

Towards the total synthesis of keramaphidin B

• Pavol Jakubec,
• Alistair J. M. Farley and
• Darren J. Dixon

Beilstein J. Org. Chem. 2016, 12, 1096–1100, doi:10.3762/bjoc.12.104

• Diels–Alder reaction as the late stage key step. After extensive purification, the authors were able to isolate keramaphidin B in just 0.3% yield, but nevertheless they provided evidence for the biosynthesis [3]. A year later, Baldwin et al. completed an alternative synthesis by performing an

• intermolecular Diels–Alder reaction and a double late stage RCM reaction to close the two macrocyclic rings; albeit the last stage afforded 1 in 1% yield after separation of various oligomeric byproducts [4]. Our group has had a long-standing research program dedicated towards the total syntheses of the

Cationic Pd(II)-catalyzed C–H activation/cross-coupling reactions at room temperature: synthetic and mechanistic studies

• Takashi Nishikata,
• Alexander R. Abela,
• Shenlin Huang and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2016, 12, 1040–1064, doi:10.3762/bjoc.12.99

• their Lewis acidity. Cationic palladium complexes [123], in particular, possess a wide breadth of reactivity, having been used to catalyze Diels–Alder [124][125], aldol and Mannich reactions [126][127][128], Wacker oxidations [129], polymerizations of alkenes [130][131], and asymmetric 1,4-additions

The synthesis of functionalized bridged polycycles via C–H bond insertion

• Jiun-Le Shih,
• Po-An Chen and
• Jeremy A. May

Beilstein J. Org. Chem. 2016, 12, 985–999, doi:10.3762/bjoc.12.97

• alternative positions, or the synthetic strategy must be completely altered as the original method is not capable of synthesizing other isomers. For example, multiple research groups have shown that the bridged bicyclo[2.2.2]octane core 1 of maoecrystal V may be constructed via an intramolecular Diels–Alder

• reaction from a functionalized 1,3-diene like 2 (Figure 2) [13][14][15][16]. However, such a reaction would not be applicable to synthesize the bicyclo[3.2.1]octane core 3 of taxuspine C, as the mechanistic requirements in a Diels–Alder cycloaddition are not met with a 1,4-diene. Strategies that may access

1H-Imidazol-4(5H)-ones and thiazol-4(5H)-ones as emerging pronucleophiles in asymmetric catalysis

• Antonia Mielgo and
• Claudio Palomo

Beilstein J. Org. Chem. 2016, 12, 918–936, doi:10.3762/bjoc.12.90

• two other examples (Scheme 7b), however, rhodanines of type 45 have been employed to produce spirocyclic compounds. The first case is an enamine/Michael tandem reaction to unsaturated enones [81] (Scheme 7b,1) and the second one is the Diels–Alder reaction with 2,4-dienals which occurs via trienamine

Separation and identification of indene–C₇₀ bisadduct isomers

• Bolong Zhang,
• Jegadesan Subbiah,
• David J. Jones and
• Wallace W. H. Wong

Beilstein J. Org. Chem. 2016, 12, 903–911, doi:10.3762/bjoc.12.88

• derivatives. In recent studies, the solar cell devices achieved power conversion efficiency as high as 7.5% for IC60BA [5] and 7.4% for IC70BA [6]. The IC70BA material used in most reports consisted of a mixture of isomers [7][8][9]. The synthesis of IC70BA involves [2 + 4] Diels–Alder cycloaddition reaction

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

• -fused pyran-3-ones and the results are reported herein. Results and Discussion For a long time, the Diels–Alder reaction of simple heterosubstituted 1,3-dienes has been considered a standard procedure to prepare highly functionalized ring systems [28]. Taking advantage of diazalactones to act as the

• 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

• halogenated lactones having the 4a,9a-fused skeleton and an ester group at position 1. The cycloaddition reaction proceeded with moderate regio- and stereoselectivity. As reported in the literature, the inverse-electron demand Diels–Alder cycloaddition of unsymmetrical olefins and oxadiazinones [33][34][35

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