5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

• CaCO-2. Lin et al. [52] developed the synthesis of pyrazolo[3,4-b]pyridine derivatives 45 via aza-Diels–Alder reaction of pyrazolylimines 43 with maleimides 44 (Scheme 8). Pyrazolylimines 43 were in turn obtained from the reaction of 5-aminopyrazole 16 with diisopropylformamide dimethyl acetal (R

• -arylmaleimides 44 in a solvent-free methodology based on microwave-assisted (80 W, 80 °C, 1.5 h) hetero-Diels–Alder reaction for the synthesis of pyrazolo[3,4-b]pyridine derivatives 45 (Scheme 8). Jiang et al. [54] described the synthesis of macrocyclane-fused pyrazolo[3,4-b]pyridine derivatives 49 by the

Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and β-ketoamides

• Irwan Iskandar Roslan,
• Kian-Hong Ng,
• Gaik-Khuan Chuah and
• Stephan Jaenicke

Beilstein J. Org. Chem. 2017, 13, 2739–2750, doi:10.3762/bjoc.13.270

• -Diels–Alder reaction [87]. Coupling between alkynoic acid and 2-aminobenzothiazole and the use of ionic liquids have also been developed [88]. Heterogeneous catalysts such as kaolin and hydrotalcites have been employed in the synthesis of benzo[4,5]thiazolo[3,2-a]pyrimidin-4-ones [89][90

Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis

• Anna Kuźnik,
• Roman Mazurkiewicz and
• Beata Fryczkowska

Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269

• vinylphosphonium salts can be used in the Diels–Alder reaction with dienes such as isoprene, 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, cyclopentadiene, and 1,3-cyclohexadiene, resulting in cyclic phosphonium salts 115 in yields of 90–96% (Scheme 66) [78]. Gelmi et al. showed that vinylphosphonium bromide 8 in

• )vinylphosphonium salt. Synthesis of 7-oxo-7H-pyrido[1,2,3-cd]perimidine derivative via nucleophilic displacement of the triphenylphosphonium group in intermediate α,β-di(methoxycarbonyl)vinylphosphonium salt. Application of vinylphosphonium salts in the Diels–Alder reaction with dienes. Synthesis of pyrroline

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

• the majority of the reported methods is a retro Diels–Alder reaction [6][13][15][16][17]. Fieser and Haddadin [17] describe IBF as a transient intermediate and Warrener and Wege [13][15] isolated IBF at −80 °C on a cold finger. The disadvantages of these methods are high reaction temperatures during

• ]+ calcd. for C12H12O5, 260.06847; found, 260.06800. Diels–Alder reaction of isobenzofuran and formation of a benzene ring in the cycloadduct. Different approaches for the synthesis of IBF (1). Reaction of in situ prepared IBF (1) with DMAD (9). Supporting Information Supporting Information File 436

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

• acid function of amino acids can be easily converted into amides or esters (Figure 1), propargylamines have been converted into acids, alcohols [12] or olefins in order to obtain natural products like angustureine and cuspareine [13]. Intramolecular Pauson–Khand reaction [14], Diels–Alder reaction [15

• ) Intramolecular Pauson–Khand reaction, R = (S)-tert-butylsulfinyl, R’ = CH2CH2OTBDPS [14]. b) Diels–Alder reaction, R = pTs, R’ = H, R’’ = Me [15]. c) Gold-catalyzed intramolecular reaction to azetidin-3-ones, R = tert-butylsulfonyl, R’ = aromatics, aliphatics [16]. d) Sonogashira cross-coupling, R = tert

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

• product [30] (Scheme 6). The analogous reaction with phenyl vinyl sulfide (22) gave the expected cyclobutane 23 exclusively. However, in the absence of ZnCl2, a mixture of 23 and 3,4-dihydro-2H-pyran 24 was obtained, with the latter compound formed through a competitive hetero-Diels–Alder reaction [30

• . Stepwise [3 + 2]-cycloadditions of dimethyl dicyanofumarate (E-1b) and dimethyl dicyanomaleate (Z-1b) with the in situ generated azomethine ylides 32. [3 + 2]-Cycloaddition of diazomethane with dimethyl dicyanofumarate (E-1b) leading to 1H-pyrazole derivative 36. Reversible Diels–Alder reaction of fulvenes

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

• of pyranes by a hetero-Diels–Alder reaction was realized. Thus, the reaction of 2-TT with formaldehyde in acetic acid at reflux led after 6 h exclusively to one regioisomer dihydropyrane 5 in 64% (Scheme 3, left) [42]. Next, the thermal Diels–Alder reaction with maleic anhydride and N-substituted

• Hetero Diels–Alder reaction: The dimer 2-TT (136.0 mL, 1.0 mmol, 1 equiv) was dissolved in acetic acid (5 mL, 0.2 M) and paraformaldehyde (45.0 mg, 1.5 mmol, 1.5 equiv) was added. The mixture was stirred and heated under reflux for 3–6 hours until completion, which was monitored by TLC. Then, the mixture

Sulfamide chemistry applied to the functionalization of self-assembled monolayers on gold surfaces

• Loïc Pantaine,
• Vincent Humblot,
• Vincent Coeffard and
• Anne Vallée

Beilstein J. Org. Chem. 2017, 13, 648–658, doi:10.3762/bjoc.13.64

• formation [12][13][14], Diels–Alder reaction [15][16] or the imine/oxime condensation [17][18]. These reactions tend to produce strong covalent interactions between the surface and the molecules in solution which ensure a stable immobilization. One limitation of the covalent strategy lies in the

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• neurodegenerative diseases and as effective insecticides, fungicides and herbicides. Keywords: biological activity; Diels–Alder reaction; Friedel–Crafts reaction; 1-indanones; Nazarov reaction; Introduction In the last few years, 1-indanone derivatives and their structural analogues have been widely used in

• provide the biggest number of carbon atoms during the synthesis of the 1-indanone benzene ring. For instance, 1,3-dienes in the Diels–Alder reaction provide 4 carbon atoms of the six ones needed to construct the benzene ring of 1-indanone compared to dienophiles which deliver only two of them. 2.1 From

• 1,3-dienes Wolf and Xu have synthesized 7-methyl substituted 1-indanone 241 utilizing 1,3-pentadiene (238) and 2-cyclopentenone (239) as starting compounds [96]. 7-Methyl substituted 1-indanone 241 has been obtained in the Diels–Alder reaction between 1,3-pentadiene (238) and 2-cyclopentenone (239

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

• Christian H. Hornung Miguel A. Alvarez-Dieguez Thomas M. Kohl John Tsanaktsidis CSIRO Manufacturing, Bag 10, Clayton South, Victoria 3169, Australia 10.3762/bjoc.13.15 Abstract This work describes the Diels–Alder reaction of the naturally occurring substituted butadiene, myrcene, with a range of

• fragrances are based on myrcene, such as geraniol, nerol, linalool, menthol, citral, citronellol or citronellal [3]. The terminal diene moiety present in myrcene allows for a reaction with a suitable dienophile following the Diels–Alder reaction mechanism. Dahill et al. describe the synthesis of the Diels

• compared to literature values. More details on the derivation of the k values and the literature references can be found in Supporting Information File 1. After the Diels–Alder reaction was optimized in batch on a small scale (typically 2 mL reaction volume) the process was scaled-up first on a Vapourtec

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

• 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

• bond-donor catalysts by Bibal and co-workers [53][54]. Tetraalkylammonium catalyst (L6)-catalyzed dearomatization of isoquinolinium salts [50]. Tetraalkylammonium catalyst L6 complexation to halogen-containing substrates [51]. Tetraalkylammonium-catalyzed aza-Diels–Alder reaction by Maruoka and co

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

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

• 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

• ] in where different stereoisomers could be obtained. Lewis-acid centers contained within the framework of zeolite beta (Zr-β, Sn-β) are useful catalysts in the Diels–Alder reaction for the production of bio-based terephthalic acid precursors, one of the monomers for the synthesis of polyethylene

• Diels–Alder reaction selectivity [28]. The DAR of cyclopentadiene with p-benzoquinone is a well-known example of cycloadditions, and some results can be found on the control of the selectivity to the different isomers. In homogeneous phase, equimolar amounts of diene and dienophile afford two isomers

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

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

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

• 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

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

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

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

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

• hydroxy group) exhibited poor enantioselectivity. These effects may suggest and support the bifunctional role played by the catalyst (Figure 8). Diels–Alder reaction An important contribution in the construction of highly substituted carbocyclic compounds was disclosed by Tan’s group in 2009. In this work

• . Diels–Alder reaction catalyzed by the aminoindanol derivative ent-41. Asymmetric Michael addition of 3-pentanone (55a) to the nitroalkenes 3 through aminocatalysis. Substrate scope extension for the asymmetric Michael addition between the ketones 55 and the nitroalkenes 3 through aminocatalysis. A