Boron-substituted 1,3-dienes and heterodienes as key elements in multicomponent processes

• Ludovic Eberlin,
• Fabien Tripoteau,
• François Carreaux,
• Andrew Whiting and
• Bertrand Carboni

Beilstein J. Org. Chem. 2014, 10, 237–250, doi:10.3762/bjoc.10.19

• chloroprene and showed no propensity to dimerize [50][51]. Exploration of the reactivity of these dienyl trifluoroborates began with Diels–Alder reactions with ethyl acrylate, methyl vinyl ketone and N-phenylmaleimide. The boron-containing cycloadducts, isolated with high yields, were subsequently cross

• -coupled to iodobenzene, 4-trifluoromethyl-1-iodobenzene and 4-iodoanisole. The regioselectivities observed in the initial Diels–Alder reactions were maintained after cross-coupling (Scheme 14). More recently, new 2-boron-substituted 1,3 dienes containing diol and triol ligands were prepared under basic

• of each 1,3-dienyl system, sequential hetero-Diels–Alder/Diels–Alder reactions (or vice versa if the order of introduction of the reagents was inversed) were carried out chemoselectively. The allylboronic ester moiety, generated in the first cycloaddition step or after the two consecutive [4 + 2

One-pot cross-enyne metathesis (CEYM)–Diels–Alder reaction of gem-difluoropropargylic alkynes

• Santos Fustero,
• Paula Bello,
• Javier Miró,
• María Sánchez-Roselló,
• Günter Haufe and
• Carlos del Pozo

Beilstein J. Org. Chem. 2013, 9, 2688–2695, doi:10.3762/bjoc.9.305

• Institut, Westfälische Wilhelms-Universität, Corrensstraße 40, D-48149 Münster, Germany 10.3762/bjoc.9.305 Abstract Propargylic difluorides 1 were used as starting substrates in a combination of cross-enyne metathesis and Diels–Alder reactions. Thus, the reaction of 1 with ethylene in the presence of 2nd

• moiety via vinylalkylidene intermediates [4][5][6]. This is an atom economical process since it is an addition reaction and non-olefin byproducts are formed. Furthermore, a sequential use of EYM and Diels–Alder reactions generates highly functionalized carbo- and heterocyclic frameworks [7][8][9][10][11

• reactions for the preparation of different difluoropropargylamides and ketones, having been subjected to intramolecular hydroaminations [23], cascade RCEYM–Diels–Alder reactions [24], [2 + 2 + 2] cycloadditions and gold-mediated dimerization reactions [25]. Although the CEYM reaction has been found to be

Stereodivergent synthesis of jaspine B and its isomers using a carbohydrate-derived alkoxyallene as C₃-building block

• Volker M. Schmiedel,
• Stefano Stefani and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2013, 9, 2564–2569, doi:10.3762/bjoc.9.291

• auxiliaries for the synthesis of enantiopure natural products such as preussin [39] and anisomycin [40] or in hetero Diels–Alder reactions [41][42]. For the stereodivergent synthesis of both enantiomers of jaspine B (1), we chose diacetoneglucose-derived alkoxyallene 11, which is easily accessible on gram

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

Sequential Diels–Alder/[3,3]-sigmatropic rearrangement reactions of β-nitrostyrene with 3-methyl-1,3-pentadiene

• Peter A. Wade,
• Alma Pipic,
• Matthias Zeller and
• Panagiota Tsetsakos

Beilstein J. Org. Chem. 2013, 9, 2137–2146, doi:10.3762/bjoc.9.251

• nitroalkene Diels–Alder reactions have been proposed. Denmark et al. favor a stepwise process proceeding via a zwitterion intermediate [11][14]. Alkene stereointegrity is normally retained, presumably owing to a cyclic conformation dictated by charge interaction between the cation center and tin nitronate

The chemistry of isoindole natural products

• Klaus Speck and
• Thomas Magauer

Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243

• developed (Figure 1). Compared to the synthesis of indoles, where a number of named-reactions have been reported, only conventional methods are used for the related isoindole motif. For the construction of this rare skeleton inter- and intramolecular Diels–Alder reactions are one of the most powerful

Thiourea-catalyzed Diels–Alder reaction of a naphthoquinone monoketal dienophile

• Carsten S. Kramer and
• Stefan Bräse

Beilstein J. Org. Chem. 2013, 9, 1414–1418, doi:10.3762/bjoc.9.158

• catalyst and substrate. Also the naphthoquinone monoketal Diels–Alder reactions were quenched after 28 d. After that time no further conversion was observed and some starting material could be recovered. Nevertheless it has to be considered that the catalyst facilitates the construction of a very congested

Cascade radical reaction of substrates with a carbon–carbon triple bond as a radical acceptor

• Hideto Miyabe,
• Ryuta Asada and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2013, 9, 1148–1155, doi:10.3762/bjoc.9.128

• 2002 that hydroxamic acid derivatives are useful achiral templates in enantioselective Diels–Alder reactions [69][70]. To study the effect of hydroxamate ester as an achiral template in the intermolecular radical reaction, our experiments began with the investigation of cascade radical addition

Diastereoselective synthesis of nitroso acetals from (S,E)-γ-aminated nitroalkenes via multicomponent [4 + 2]/[3 + 2] cycloadditions promoted by LiCl or LiClO₄

• Leandro Lara de Carvalho,
• Robert Alan Burrow and
• Vera Lúcia Patrocinio Pereira

Beilstein J. Org. Chem. 2013, 9, 838–845, doi:10.3762/bjoc.9.96

• related). The cycloadditions with 5a–c were performed in concentrated lithium salt solutions following similar protocols described in the literature in which lithium perchlorate 5.0 M in diethyl ether (LPDE) was employed successful as a promoter in Diels–Alder reactions. This solution was found to be a

A versatile and efficient approach for the synthesis of chiral 1,3-nitroamines and 1,3-diamines via conjugate addition to new (S,E)-γ-aminated nitroalkenes derived from L-α-amino acids

• Vera Lúcia Patrocinio Pereira,
• André Luiz da Silva Moura,
• Daniel Pais Pires Vieira,
• Leandro Lara de Carvalho,
• Eliz Regina Bueno Torres and
• Jeronimo da Silva Costa

Beilstein J. Org. Chem. 2013, 9, 832–837, doi:10.3762/bjoc.9.95

• hetero-Diels–Alder reactions [27][28][29][30][31] and even participate in cross-coupling reactions [32]. Due to this notable reactivity, obtaining new chiral and achiral nitroalkenes is of great importance in synthetic organic chemistry. Achiral nitroalkenes, specifically the chemically stable β-trans

Asymmetric synthesis of a highly functionalized bicyclo[3.2.2]nonene derivative

• Toshiki Tabuchi,
• Daisuke Urabe and
• Masayuki Inoue

Beilstein J. Org. Chem. 2013, 9, 655–663, doi:10.3762/bjoc.9.74

• ; m.p. 55 °C; [α]D20 +260 (c 0.37, CHCl3). Other analytical data of 1 were identical to those reported by our group previously [11]. Structure of ryanodine and the Diels–Alder reactions for construction of the potential intermediates of ryanodine. Asymmetric synthesis of 7 and determination of the

Facile synthesis of functionalized tetrahydroquinolines via domino Povarov reactions of arylamines, methyl propiolate and aromatic aldehydes

• Jing Sun,
• Hong Gao,
• Qun Wu and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2012, 8, 1839–1843, doi:10.3762/bjoc.8.211

• reaction; tetrahydroquinoline; Introduction The Diels–Alder reaction is recognized as a powerful reaction in synthetic strategies for the production of natural and unnatural polycarbocycles and polyheterocycles [1][2][3]. Therefore, the hetero-Diels–Alder reactions and domino reaction procedures have been

Asymmetric Brønsted acid-catalyzed aza-Diels–Alder reaction of cyclic C-acylimines with cyclopentadiene

• Magnus Rueping and
• Sadiya Raja

Beilstein J. Org. Chem. 2012, 8, 1819–1824, doi:10.3762/bjoc.8.208

• construction of optically active, nitrogen-containing, six-membered rings, such as tetrahydroquinolines and piperidines. N-heterocycles are found in a wide range of natural products and many biologically active compounds [1][2][3][4]. To date, most aza-asymmetric Diels–Alder reactions have been catalyzed by

Highly enantioselective access to cannabinoid-type tricyles by organocatalytic Diels–Alder reactions

• Stefan Bräse,
• Nicole Volz,
• Franziska Gläser and
• Martin Nieger

Beilstein J. Org. Chem. 2012, 8, 1385–1392, doi:10.3762/bjoc.8.160

• organocatalytic Diels–Alder reactions to build up a tricyclic system. Herein, an asymmetric induction up to 96% enantiomeric excess was obtained by the use of imidazolidinone catalysts. This approach can be utilized to construct the tricyclic system in numerous natural products, in particular the scaffold of

• ). An assortment of natural products synthesized by Diels–Alder reactions. Intermediates towards the total synthesis of (−)-Δ9-tetrahydrocannabinol (4). Formation of the iminium-ion. Crystal structure of the side product from the reaction of 13. Confirmation of the relative configuration with NOESY

Recyclable fluorous cinchona alkaloid ester as a chiral promoter for asymmetric fluorination of β-ketoesters

• Wen-Bin Yi,
• Xin Huang,
• Zijuan Zhang,
• Dian-Rong Zhu,
• Chun Cai and
• Wei Zhang

Beilstein J. Org. Chem. 2012, 8, 1233–1240, doi:10.3762/bjoc.8.138

• cinchona alkaloids for catalytic Diels–Alder reactions [23][24]. Introduced in this paper is a new fluorous cinchona alkaloid ester for flourination of β-ketoesters. It is part of our recent effort on the development of recyclable fluorous reagents and organocatalysts for asymmetric synthesis [25][26][27

Synthesis and structure of tricarbonyl(η⁶-arene)chromium complexes of phenyl and benzyl D-glycopyranosides

• Thomas Ziegler and
• Ulrich Heber

Beilstein J. Org. Chem. 2012, 8, 1059–1070, doi:10.3762/bjoc.8.118

• carbohydrate-derived chromium complexes that have been described in the literature so far. Complexes of type A and B were obtained from the corresponding glycopyranosides and were studied as substrates for chiral-auxiliary-directed asymmetric ortholithiation and as catalysts for enantioselective Diels–Alder

• reactions [9][10][11][12]. Tricarbonylchromium complexes of type C and D were obtained via benzannulation of glucal-derived pentacarbonylchromium carbenes or by reaction of alkynyl C-glycosides with pentacarbonylchromium carbenes [13]. Further syntheses and characterizations of more examples of carbohydrate

Expanding the chemical diversity of spirooxindoles via alkylative pyridine dearomatization

• Chunhui Dai,
• Bo Liang and
• Corey R. J. Stephenson

Beilstein J. Org. Chem. 2012, 8, 986–993, doi:10.3762/bjoc.8.111

• ]oxazino derivatives from N-substituted isatins and 1,3-dicarbonyl compounds with pyridine derivatives is reported. The reactions provided good to excellent yields. Further exploration of the molecular diversity of these compounds is demonstrated through Diels–Alder reactions. Keywords: chemical diversity

An intramolecular inverse electron demand Diels–Alder approach to annulated α-carbolines

• Zhiyuan Ma,
• Feng Ni,
• Grace H. C. Woo,
• Sie-Mun Lo,
• Philip M. Roveto,
• Scott E. Schaus and
• John K. Snyder

Beilstein J. Org. Chem. 2012, 8, 829–840, doi:10.3762/bjoc.8.93

• the library members produced in yields greater than 85%. Purification by LC–MS produced the final library. Conclusion Isatin-derived 1,2,4-triazines have proven to be excellent heteroaromatic azadienes for intramolecular inverse electron demand Diels–Alder reactions with tethered alkynyl dienophiles

Sonogashira–Hagihara reactions of halogenated glycals

• Dennis C. Koester and
• Daniel B. Werz

Beilstein J. Org. Chem. 2012, 8, 675–682, doi:10.3762/bjoc.8.75

• and Heck reactions, respectively [21]. The dienes obtained during these transformations were successfully converted in Diels–Alder reactions to afford carbocyclic chiral compounds with a sugar backbone. In 2008, Gagné introduced a Ni-mediated Negishi coupling to synthesize alkyl- and aryl-C-glycosides

Valence isomerization of cyclohepta-1,3,5-triene and its heteroelement analogues

• Helen Jansen,
• J. Chris Slootweg and
• Koop Lammertsma

Beilstein J. Org. Chem. 2011, 7, 1713–1721, doi:10.3762/bjoc.7.201

• -oxabicyclo[2.3.0]hepta-3,6-diene (13) [38][51], while under thermal, photochemical or acidic conditions, the three-membered ring of bicyclic 4 opens, generating phenol [67][68], in analogy to the all-carbon norcaradiene (2), which gives toluene. In addition, 4 undergoes highly selective Diels–Alder reactions

PEG-embedded KBr₃: A recyclable catalyst for multicomponent coupling reaction for the efficient synthesis of functionalized piperidines

• Sanny Verma,
• Suman L. Jain and
• Bir Sain

Beilstein J. Org. Chem. 2011, 7, 1334–1341, doi:10.3762/bjoc.7.157

• –Alder reactions [22][23], intramolecular Michael reactions [24], intramolecular Mannich reactions onto iminium ions [25], tandem cyclopropane ring-opening/Conia-ene cyclizations [26], and aza-Prins-cyclization [27][28][29], have been reported for the synthesis of piperidines. However, these methods

• compounds [15][16][17]. Also the piperidine ring is present in many natural products [18][19] such as alkaloids, which are responsible for a number of unique activities including anti-hypertensive [20], anticonvulsant and anti-inflammatory activities [21]. Many conventional methods, such as imino Diels

A simple and convenient one-pot synthesis of substituted isoindolin-1-ones via lithiation, substitution and cyclization of N'-benzyl-N,N-dimethylureas

• Keith Smith,
• Gamal A. El-Hiti,
• Amany S. Hegazy and
• Benson Kariuki

Beilstein J. Org. Chem. 2011, 7, 1219–1227, doi:10.3762/bjoc.7.142

• ]. Also, some members that possess this moiety have shown interesting biological properties [9][10][11][12][13][14][15]. Several traditional methods are available for the synthesis of isoindolinones [16][17][18][19][20][21][22][23][24][25], based on the use of Grignard reagents [26], Diels–Alder reactions

High chemoselectivity in the phenol synthesis

• Matthias Rudolph,
• Melissa Q. McCreery,
• Wolfgang Frey and
• A. Stephen K. Hashmi

Beilstein J. Org. Chem. 2011, 7, 794–801, doi:10.3762/bjoc.7.90

• , and these could even be trapped by Diels–Alder reactions. In addition, labelling studies were carried out and the electronic influence of substituents was investigated [21]. Computational studies as well as side-products produced in the reaction pointed towards intermediates A and B (Scheme 1) [22][23

Ene–yne cross-metathesis with ruthenium carbene catalysts

• Cédric Fischmeister and
• Christian Bruneau

Beilstein J. Org. Chem. 2011, 7, 156–166, doi:10.3762/bjoc.7.22

• products were obtained in excellent yields at low temperature (Scheme 12) [67]. The cross-metathesis of terminal enol ethers with terminal and internal alkynes in the presence of catalyst II has led to the regioselective formation of electron rich dienes, precursors of choice for Diels–Alder reactions

• ethylene, Diels–Alder reactions have been attempted starting from the more substituted dienes arising from metathesis of alkynes with higher olefins. It must be noted that the regioselectivity of these EYCM always leads to 1,3-dienes with a terminal and a substituted methylene group. It has been shown that

• the disubstituted double bond possessing a (Z)-configuration does not participate in Diels–Alder reactions [61]. Using the EYCM/Diels–Alder sequence, tetrahydropyridines [57], substituted phenylalanines [71][72], modified porphyrins [73], carbocycle-linked oligosaccharides [74] and heterocycles [75

Addition of lithiated enol ethers to nitrones and subsequent Lewis acid induced cyclizations to enantiopure 3,6-dihydro-2H-pyrans – an approach to carbohydrate mimetics

• Fabian Pfrengle and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, No. 75, doi:10.3762/bjoc.6.75

• efficient preparation include Prins cyclizations, intramolecular substitutions, ring closure metathesis, and hetero Diels–Alder reactions [1][2]. Our group recently reported the synthesis of enantiopure aminopyrans employing as the key step a Lewis acid induced rearrangement of 1,2-oxazines to bicyclic