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

(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

• a variety of transformations. Utilizing the primary amine-thiourea 18, an enantioselective formal aza-Diels–Alder reaction of enones 12 and 13 was reported. In this reaction the enamine is formed from the side of the methyl ketone, which is conjugated with the pre-existing double bond, providing the

• electron-rich diene, which reacts with substituted dihydroisoquinoline 14 and dihydro-β-carboline 15, so that cyclohexanone derivatives 16 and 17 will be produced, respectively (Scheme 8) [19]. Also, a cyclic derivative of 13 was utilized (not shown). This aza-Diels–Alder reaction provides products with

• , the product was obtained in 78–90% yield and 15–92% ee. Finally, β-substituted α,β-unsaturated aldehydes were completely unreactive. In 2012, a proposed inverse electron-demand Diels–Alder reaction was reported by Wang and co-workers, obtaining enantiopure products 33, starting from diene 31 and

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

• Melchiorre. A Diels–Alder reaction of indole-2,3-quinodimethane 76 (generated from 77 and the prolinol catalyst 78 ) with the enone 79 affords a tetrahydrocarbazole derivative 80. The NHC precatalyst 22 then promotes an intramolecular cross-benzoin condensation of the keto-aldehyde to furnish the tetracyclic

• cycloadducts 84 in good yield and enantioselectivity [63]. Initially, the trienamine 85 is generated by the action of prolinol catalyst 86 on the dienal 82. The former (85) then undergoes a Diels–Alder reaction with the sulfonylimine 83 to generate the keto-aldehyde 87. Finally, the NHC precatalyst 22 mediates

A quadruple cascade protocol for the one-pot synthesis of fully-substituted hexahydroisoindolinones from simple substrates

• Hong-Bo Zhang,
• Yong-Chun Luo,
• Xiu-Qin Hu,
• Yong-Min Liang and
• Peng-Fei Xu

Beilstein J. Org. Chem. 2016, 12, 253–259, doi:10.3762/bjoc.12.27

• isoindolinones have been developed. The first method was the synthesis of 3-substituted isoindolinones from the corresponding N-methylmaleimides by the Diels–Alder reaction with 1,3-butadiene followed by hydrogenation. The second and the third methods employed the corresponding dicarboxylic acids and the

Simple activation by acid of latent Ru-NHC-based metathesis initiators bearing 8-quinolinolate co-ligands

• Julia Wappel,
• Roland C. Fischer,
• Luigi Cavallo,
• Christian Slugovc and
• Albert Poater

Beilstein J. Org. Chem. 2016, 12, 154–165, doi:10.3762/bjoc.12.17

• –Alder reaction at higher temperatures, causing a mass loss during polymerization if higher temperatures are applied for the reaction. To test the pre-catalysts regarding their performance in the polymerization of DCPD, two different test-reactions were carried out: a) STA measurements to gain an insight

• polymerization of DCPD is their outstanding solubility in the neat monomer. The main challenge of the polymerization of DCPD is to guarantee an adequate mixing of monomer and catalyst to obtain a homogenous reaction mixture and moreover a steady polymerization product. DCPD is also prone to undergo a retro-Diels

Synthesis and reactivity of aliphatic sulfur pentafluorides from substituted (pentafluorosulfanyl)benzenes

• Norbert Vida,
• Jiří Václavík and
• Petr Beier

Beilstein J. Org. Chem. 2016, 12, 110–116, doi:10.3762/bjoc.12.12

• : dearomatization; decarboxylation; Diels–Alder reaction; oxidation; pentafluorosulfanyl group; Introduction Fluorinated organic compounds have been one of the foci of chemical industry for the last several decades. The unique properties of fluorine atoms and fluorinated groups have been exploited in various

• oxidation of aromatics. Benzoquinone 12 is a solid material with good stability at −20 °C. Several standard reactions were investigated. Reduction to hydroquinone 15 using catalytic palladium was very efficient (Scheme 5). The Diels–Alder reaction with cyclopentadiene proceeded in a high yield at ambient

• acid 4, some basic chemical reactivity studies were performed. When heated to about 125 °C under reduced pressure, acid 4 eliminated water to afford anhydride 20 in a good yield. Anhydride 20 underwent a Diels–Alder reaction with cyclopentadiene at ambient temperature to provide a mixture of endo and

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

• ][24][25][26]. Several new developments in the related hetero-Diels–Alder reaction of acylnitroso species have also been reported recently [27][28][29][30]. These methodologies generally involve in situ generation of the acylnitroso species, achieved using a variety of oxidants including vanadium- [28

• trapped by hetero-Diels–Alder reaction with dienes [54][55], and detection of the resulting hetero-Diels–Alder adducts used to confirm the formation of free nitroso intermediates. Thus trapping experiments were conducted using isoprene (14) to investigate the formation of a nitroso species in this

• reaction. First a 1:1 mixture of cycloadducts 15 and 16 was synthesised as a reference sample using Kirby’s conditions for the hetero-Diels–Alder reaction (N-Boc-hydroxylamine (8), isoprene (14) and sodium periodate, Scheme 3a) [54][55]. Then isoprene (14) and N-Boc-hydroxylamine (8) were combined in

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

• Tatjana Huber,
• Lara Weisheit and
• Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

• ester 75. Finally, an elegant cascade reaction involving an aldol condensation, followed by a hetereo Diels–Alder reaction closed the last three rings and antheliolide A (18) was obtained in 74% yield. In summary, the successful total synthesis of antheliolide A proceeded in 25 linear steps with an

Recent highlights in biosynthesis research using stable isotopes

• Jan Rinkel and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2015, 11, 2493–2508, doi:10.3762/bjoc.11.271

• group. The energy barrier of a distorted benzene ring would then be compensated by rearomatization in 23 after intramolecular Diels–Alder reaction. This mechanism would involve a 1,2-hydride shift and a nucleophilic attack of water at C-2’. The second discussed route starts with a nucleophilic attack of

• the phenolic oxygen at C-6 to close the macrocycle in 25. In this mechanism, the aromaticity of the phenol ring remains untouched. Intramolecular Diels–Alder reaction gives rise to the hexacyclic system 26, which would then be oxidized to pyrrocidine A (24) at C-2’. In contrast to route A, the

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

• yields, referred to the starting compounds 3/3', are reported in Scheme 2. No epimerisation reactions occurred during the hydrolytic processes as demonstrated via 2D NMR experiments (COSY, HSQC). Discussion In the Diels–Alder reaction of vinylindoles 1 with methyl 2-acetamidoacrylate (2), among tested

• 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

Stereochemistry of ring-opening/cross metathesis reactions of exo- and endo-7-oxabicyclo[2.2.1]hept-5-ene-2-carbonitriles with allyl alcohol and allyl acetate

• Piotr Wałejko,
• Michał Dąbrowski,
• Lech Szczepaniak,
• Jacek W. Morzycki and
• Stanisław Witkowski

Beilstein J. Org. Chem. 2015, 11, 1893–1901, doi:10.3762/bjoc.11.204

• reaction may be improved by using neat reaction conditions. Experimental A mixture of 1 and 2 (1.6:1) is readily available from the Diels–Alder reaction of furan and acrylonitrile according to the literature procedure [28][29]. The pure isomers were isolated by column chromatography. The 1H and 13C NMR

The simple production of nonsymmetric quaterpyridines through Kröhnke pyridine synthesis

• Isabelle Sasaki,
• Jean-Claude Daran and
• Gérard Commenges

Beilstein J. Org. Chem. 2015, 11, 1781–1785, doi:10.3762/bjoc.11.193

• pathway [17][20], or a Suzuki–Miyaura cross-coupling reaction [21]. The use of triazine derivatives (which under particular conditions undergo an inverse Diels–Alder reaction) can also produce oligopyridines [22]. On the other hand, there are a limited number of reports dealing with the preparation of

Pyridinoacridine alkaloids of marine origin: NMR and MS spectral data, synthesis, biosynthesis and biological activity

• Louis P. Sandjo,
• Victor Kuete and
• Maique W. Biavatti

Beilstein J. Org. Chem. 2015, 11, 1667–1699, doi:10.3762/bjoc.11.183

• quick and economically accessible for developing styelsamine B (4) and cystodytin J (1) bioactive derivatives. Synthesis of sebastianine A (38) and its regioisomer (39) The first step of the sebastianine A synthesis was based on a Diels–Alder reaction between a pyrroloquinone used as the dienophile and

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

• Abstract A new tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR) has been carried out. It involves conjugated ketones, esters or amides bearing a remote olefin and aromatic alkynes as the starting materials. The overall process enables the preparation of a small family of

• bonds, expanding the utility of metathesis processes beyond olefinic substrates [8][9]. The inherent tandem nature of enyne metathesis is particularly appealing in its combination with the Diels–Alder reaction. This tandem protocol is well suited for addressing a broad range of complex molecules since

• the presence of second generation Hoveyda–Grubbs catalyst [23]. After the initial formation of the trienic unit, an intramolecular Diels–Alder reaction (IMDAR) rendered highly functionalized bicyclic derivatives in a very efficient manner. More recently, a multicomponent CEYM–intermolecular hetero

Thermal properties of ruthenium alkylidene-polymerized dicyclopentadiene

• Yuval Vidavsky,
• Yotam Navon,
• Yakov Ginzburg,
• Moshe Gottlieb and
• N. Gabriel Lemcoff

Beilstein J. Org. Chem. 2015, 11, 1469–1474, doi:10.3762/bjoc.11.159

• equilibrates and further ruthenium–alkylidene metathesis with neighboring double bonds may be promoted. Alternatively, thermal decomposition of DCPD (or larger oligomers) to cyclopentadiene (CPD) by a retro-Diels–Alder reaction could also explain the observed phenomenon, although unlikely at room temperature

Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity

• Karolina Żukowska,
• Eva Pump,
• Aleksandra E. Pazio,
• Krzysztof Woźniak,
• Luigi Cavallo and
• Christian Slugovc

Beilstein J. Org. Chem. 2015, 11, 1458–1468, doi:10.3762/bjoc.11.158

• substrate-induced activation is impeded. This effect turned out to be of particular relevance when the polymerization of dicyclopentadiene is regarded. Because polymerizations were carried out in open reaction vessels, the retro-Diels–Alder reaction of 23, releasing volatile cyclopentadiene, is a concurring

Cross-metathesis reaction of α- and β-vinyl C-glycosides with alkenes

• Ivan Šnajdr,
• Kamil Parkan,
• Filip Hessler and
• Martin Kotora

Beilstein J. Org. Chem. 2015, 11, 1392–1397, doi:10.3762/bjoc.11.150

• cycloaddition reactions providing indolyl C-deoxyribosides [6], cyclopentenonyl C-deoxyribosides [9], triazolyl C-deoxyribosides [12][13], carboranyl C-deoxyribosides [7], and finally also in Diels–Alder reaction with cyclobutadiene derivatives [8]. Despite of the above mentioned transformations, alkynyl C

Design and synthesis of polycyclic sulfones via Diels–Alder reaction and ring-rearrangement metathesis as key steps

• Sambasivarao Kotha and
• Rama Gunta

Beilstein J. Org. Chem. 2015, 11, 1373–1378, doi:10.3762/bjoc.11.148

• Sambasivarao Kotha Rama Gunta Department of Chemistry, Indian Institute of Technology-Bombay, Powai, Mumbai-400 076, India, Fax: 022-25767152 10.3762/bjoc.11.148 Abstract Here, we describe a new and simple synthetic strategy to various polycyclic sulfones via Diels–Alder reaction and ring

• . Interestingly the starting materials used are simple and commercially available. Keywords: alkenylation; Diels–Alder reaction; ring-rearrangement metathesis; sulfones; Introduction Sulfones [1][2][3][4][5][6][7][8] are popular building blocks [9] in organic synthesis. They are also useful substrates for the

Spiro annulation of cage polycycles via Grignard reaction and ring-closing metathesis as key steps

• Sambasivarao Kotha,
• Mohammad Saifuddin,
• Rashid Ali and
• Gaddamedi Sreevani

Beilstein J. Org. Chem. 2015, 11, 1367–1372, doi:10.3762/bjoc.11.147

• ) reaction as a key step is described. The structures of three new cage compounds 7, 12 and 18 were confirmed by single crystal X-ray diffraction studies. Keywords: cage molecules; Diels–Alder reaction; Grignard reaction; ring-closing metathesis; spirocycles; Introduction Design and synthesis of

• Claisen rearrangement and RCM as key steps [21][30]. Here, we have prepared the cage dione 10 by the known route involving two atom-economic protocols such as Diels–Alder reaction and [2 + 2] photocycloaddition [42][43][44][45] (Scheme 1). Later, the hexacyclic cage dione 10 was subjected to a Grignard

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• muscopyridine (73, 89%). [4 + 2] Cycloaddition (Diels–Alder reaction): In 2003, Tochtermann and co-workers [193] have synthesized a bis[10]paracyclophane with two chiral planes and one chiral axis via the DA reaction as a key step. The bifuran derivative 331 was subjected to a DA sequence with dimethyl

Design and synthesis of fused polycycles via Diels–Alder reaction and ring-rearrangement metathesis as key steps

• Sambasivarao Kotha and
• Ongolu Ravikumar

Beilstein J. Org. Chem. 2015, 11, 1259–1264, doi:10.3762/bjoc.11.140

• Sambasivarao Kotha Ongolu Ravikumar Department of Chemistry, Indian Institute of Technology-Bombay, Powai, Mumbai-400 076, India, Fax: 022-25767152 10.3762/bjoc.11.140 Abstract Atom efficient processes such as the Diels–Alder reaction (DA) and the ring-rearrangement metathesis (RRM) have been

• : Diels–Alder reaction; Grignard addition; ring-rearrangement metathesis; polycycles; Introduction Design and synthesis of complex polycycles in a minimum number of steps will enhance the overall synthetic economy of the preparation of a target molecule. The ring-rearrangement metathesis (RRM) is a

• studied. Results and Discussion Our strategy to polycycles involves a Diels–Alder reaction (DA) [23][24][25], a Grignard addition [26] and a RRM as key steps. To begin with, a double DA reaction of cyclopentadiene (1) with 1,4-benzoquinone (2) gave the known bis-adduct 3 [27][28]. Later, it was reacted

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

• visually analogous to a titration, with the intensely colored PTAD serving as the indicator. In case of the transformation 21→38, the color changes from red to yellow and is hence less readily monitored. When an excess of 36 is employed in the Diels–Alder reaction, the overall picture changes (Scheme 11

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

• yielding thiopyran derivatives. The hetero-Diels–Alder reaction occurs in a chemo- and regioselective manner. The initially formed [4 + 2] cycloadducts rearrange via a 1,3-hydrogen shift sequence to give the final products. The latter were smoothly oxidized by treatment with mCPBA to the corresponding

• type 4a (Scheme 1) [9][10][11]. The same transformation occurred faster under photolytic conditions [9][12]. The hetero-Diels–Alder reaction of 4-substituted analogues of 1a with in situ generated benzyne is also known [13]. Heteroaromatic thioketones are reported to undergo a hetero-Diels–Alder

• performed under thermal conditions, and in both cases, new polycyclic thiopyran derivatives 5b and 5c, respectively, were formed regioselectively and obtained in good yields (94 and 61%, respectively). In order to test the scope and limitations of the hetero-Diels–Alder reaction with thioketones and

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

• -4,7-(ethylphosphinidene)indene (2e) only upon heating up to 60 °C. With further heating to 120 °C with N-phenylmaleimide, the cycloadducts 2a–c and 2e undergo the retro-Diels–Alder reaction and form only one product of the [4 + 2] cycloaddition reaction 3a–с, 3e with good yields up to 65%. Keywords

• : cycloaddition; phospholes; phosphorus heterocycles; polycyclic phosphines; retro-Diels–Alder reaction; Introduction Phospholes are weakly aromatic heterocycles and demonstrate rather different properties from those of their S, N and O counterparts [1][2]. Due to low their aromaticity, phospholes are of

• first example of [4 + 2] cycloaddition between two diphosphole molecules where 1,2-diphosphole acts as a diene and a dienophile in one reaction. Therefore, these isomeric cycloadducts, 2a–с, can be a source of reactive 1,2-diphospholes containing EWGs 1a–с in the retro-Diels–Alder reaction [19]. Indeed