Carbohydrate-auxiliary assisted preparation of enantiopure 1,2-oxazine derivatives and aminopolyols

• Marcin Jasiński,
• Dieter Lentz and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2012, 8, 662–674, doi:10.3762/bjoc.8.74

• the level of diastereoselectivity was only low to moderate, and the interpretation should therefore not be exaggerated. Alternative conformations explaining the results are certainly possible. The fragmentation of the primarily formed allenyl N-hydroxylamines of type 2 leading to 1,3-dienes such as 4

Alkoxide-induced ring opening of bicyclic 2-vinylcyclobutanones: A convenient synthesis of 2-vinyl-substituted 3-cycloalkene-1-carboxylic acid esters

• Xiufang Ji,
• Zhiming Li,
• Quanrui Wang and
• Andreas Goeke

Beilstein J. Org. Chem. 2012, 8, 650–657, doi:10.3762/bjoc.8.72

• reaction of ketenes (R2C=C=O) with alkenes under thermal conditions to give cyclobutanone products is generally described as an [π2s + π2a] process from orbital symmetry considerations. However, there is strong evidence that formation of the Staudinger-type cycloadducts by using cyclic (s-cis) 1,3-dienes

Chemistry of polyhalogenated nitrobutadienes, 10: Synthesis of highly functionalized heterocycles with a rigid 6-amino-3-azabicyclo[3.1.0]hexane moiety

• Viktor A. Zapol’skii,
• Jan C. Namyslo,
• Armin de Meijere and
• Dieter E. Kaufmann

Beilstein J. Org. Chem. 2012, 8, 621–628, doi:10.3762/bjoc.8.69

• -butadiene (3) [1] is one of the most prominent members of this rather new class of dienes. During the past nine years we have published the syntheses of a wide range of diverse substance classes, applying this useful starting material [2][3][4][5][6][7]. The present work focuses on pharmacologically

• reactions, namely the conversion of the 1-amino-2,2-dichlorovinyl group to a dichloromethyl ketone and, in addition, the reductive bisdechlorination of a dichloromethyl group were recently published by our group [5][43]. Conclusion Regioselective reactions of the nitrotrichlorobuta-1,3-dienes 3 and 4, some

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

• -1,3,5-triene into the corresponding bicyclo[4.1.0]hepta-2,4-dienes is reviewed to show the impact of the heteroatom on the stability of both valence isomers. The focus is on the parent systems and their synthetic applications. Keywords: aromaticity; cycloheptatriene; heteroatom; valence isomerization

Efficient synthesis of 1,3-diaryl-4-halo-1H-pyrazoles from 3-arylsydnones and 2-aryl-1,1-dihalo-1-alkenes

• Yiwen Yang,
• Chunxiang Kuang,
• Hui Jin,
• Qing Yang and
• Zhongkui Zhang

Beilstein J. Org. Chem. 2011, 7, 1656–1662, doi:10.3762/bjoc.7.195

• ], alkenyl arenes [19], 1,3-dienes [20][21], α,β-unsaturated esters [19][22] and nitriles [23], phosphane oxides [24] or with alkynyl silanes [18], stannanes [18][25][26], arenes [27][28], esters [29][30][31][32][33], boronic esters [34][35]. However, the cycloaddition of sydnones with 1,1-dihaloalkenes is

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• -dienes) [5][6][7][8][9][10][11][12]. Today it is well known that the excellent reactivity of these group-11 catalysts can in part be explained in terms of relativistic effects, particularly marked in the case of gold [13][14], that induce the contraction of 6s and the expansion of 5d orbitals. As a

• , dienes and allenes in a similar way [18][19][20][21][22], nucleophiles seem to have a kinetic preference for attacking activated alkynyl systems, which warrants high chemoselectivities. Based on this reactivity pattern, several groups have demonstrated that certain substrates containing an alkyne and a

• external vinyl ether 4, leading to interesting 9-oxabicyclo[3.3.1]nona-4,7-dienes 5 in good yields (Scheme 2). In view of the highly stereoselective outcome of these reactions and the requirement of an alkoxy or acyloxy group at the propargylic position of 3, the authors proposed a reaction pathway based

Asymmetric Au-catalyzed cycloisomerization of 1,6-enynes: An entry to bicyclo[4.1.0]heptene

• Alexandre Pradal,
• Chung-Meng Chao,
• Patrick Y. Toullec and
• Véronique Michelet

Beilstein J. Org. Chem. 2011, 7, 1021–1029, doi:10.3762/bjoc.7.116

• process, as the cyclic alkene 3e was isolated in 61% yield (Table 2, entry 4). In the case of non-substituted enyne 1b (Table 2, entry 5), the bicyclic alkenyl derivative 3b was isolated in low yield and ee: The synthesis of 3b was accompanied by the formation of known 1,3- and 1,4-dienes (5% and 10

One-pot Diels–Alder cycloaddition/gold(I)-catalyzed 6-endo-dig cyclization for the synthesis of the complex bicyclo[3.3.1]alkenone framework

• Boubacar Sow,
• Gabriel Bellavance,
• Francis Barabé and
• Louis Barriault

Beilstein J. Org. Chem. 2011, 7, 1007–1013, doi:10.3762/bjoc.7.114

• ). One-pot cycloaddition/cyclization of dienes 19 and 20 (Z/E = 6:1 ca.) with N-phenylmaleimide gave ketones 24 and 26 in 93 and 88% yield, respectively, as the sole diastereomers (Table 1, entries 1 and 3). The use of maleic anhydride as the dienophile also provided the desired products 25 and 27

• stereoselectively transformed into the desired bridgehead ketones 30 and 31 in 77 and 48% yields, respectively. Interestingly, hemiketal 32 was isolated in 56% yield, which suggests that the MOM group was cleaved during the Au(I)-catalyzed carbocyclization. It is important to note that the E-isomer of dienes 19–23

• (minor compound) do not react with the dienophiles, but rather isomerized to the Z-form under the reaction conditions, thus, ensuring the formation of a single diastereomer. To extend the scope of the reaction, other dienes possessing internal alkynes were also investigated (Table 2). It can be seen that

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• + 2] cycloaddition product in very good yield (Scheme 41). Enynes [110][111][112][113][114][115][116], diynes [117][118][119][120], allenynes [121][122][123][124][125][126][127][128], and dienes [129][130][131] are common substrates for intramolecular cycloaddition reactions. Porcel et al. found that

Synthetic applications of gold-catalyzed ring expansions

• David Garayalde and
• Cristina Nevado

Beilstein J. Org. Chem. 2011, 7, 767–780, doi:10.3762/bjoc.7.87

• affords predominately dienes 4 and 5 (Scheme 1, reaction 1: c for 4 and 5). By contrast, gold salts show almost no preference for the activated C–C sigma bond in the substrate. However, in the case of 2,2,4,4-tetramethylbicyclo[1.1.0]butane (6), the reaction was completely selective and gave 2,5-dimethyl

Metathesis access to monocyclic iminocyclitol-based therapeutic agents

• Ileana Dragutan,
• Valerian Dragutan,
• Carmen Mitan,
• Hermanus C.M. Vosloo,
• Lionel Delaude and
• Albert Demonceau

Beilstein J. Org. Chem. 2011, 7, 699–716, doi:10.3762/bjoc.7.81

• ) and L-1-deoxyallonojirimycin (122) (Scheme 21) starting from protected diacetone glucose 115 [71]. Different pathways were devised for 91 and 122 via the epimeric RCM precursors 117 and 120, respectively. High yielding cyclization of these dienes, in the presence of the 1st-generation Grubbs catalyst

The arene–alkene photocycloaddition

• Ursula Streit and
• Christian G. Bochet

Beilstein J. Org. Chem. 2011, 7, 525–542, doi:10.3762/bjoc.7.61

• electrocyclic ring opening to yield eight-membered ring systems (Scheme 25) [73][80]. Another possibility to further transform the intermediates are Diels–Alder cycloadditions of the dienes formed by the ortho photocycloaddition [81]. Furthermore, Scharf demonstrated that he could trigger a photochemical

• of conjugated dienes or a second arene (usually higher aromatics), this photocycloaddition can also be carried out in a [4 + 4] mode to afford bicyclo[4.2.2]decatrienes and more complex homocycles [91][94][95]. In the non-sensitized irradiation of dianthryls, the [4 + 4] photocycloaddition [91

Oxidative allylic rearrangement of cycloalkenols: Formal total synthesis of enantiomerically pure trisporic acid B

• Silke Dubberke,
• Muhammad Abbas and
• Bernhard Westermann

Beilstein J. Org. Chem. 2011, 7, 421–425, doi:10.3762/bjoc.7.54

• building block for the synthesis of dienes leading to nagilactones, 1b has been utilized for the preparation of ferroelectric liquid crystals [14][15]. Starting from (−)-1c a vast number of cyclohexene carboxylic acid-based natural products bearing additional alkyl substituents can be synthesized. These

An efficient and practical entry to 2-amido-dienes and 3-amido-trienes from allenamides through stereoselective 1,3-hydrogen shifts

• Ryuji Hayashi,
• John B. Feltenberger,
• Andrew G. Lohse,
• Mary C. Walton and
• Richard P. Hsung

Beilstein J. Org. Chem. 2011, 7, 410–420, doi:10.3762/bjoc.7.53

• Ryuji Hayashi John B. Feltenberger Andrew G. Lohse Mary C. Walton Richard P. Hsung Department of Chemistry and Division of Pharmaceutical Sciences, University of Wisconsin, Madison, WI 53705 10.3762/bjoc.7.53 Abstract Preparations of de novo acyclic 2-amido-dienes and 3-amido-trienes through 1,3

• -configuration. In addition, 6π-electron electrocyclic ring-closure could be carried out with 3-amido-trienes to afford cyclic 2-amido-dienes, and such electrocyclic ring-closure could be rendered in tandem with the 1,3-hydrogen shift. Keywords: allenamides; 2-amido-dienes; 3-amido-trienes; electrocyclic ring

• -closure; 1,3-hydrogen shift; isomerization; Introduction While allene isomerization to afford conjugated dienes is a well-known and thermodynamically favourable process, it is not trivial kinetically. A concerted allene isomerization leading to a diene involves a 1,3-hydrogen shift, which constitutes a

Rh-Catalyzed rearrangement of vinylcyclopropane to 1,3-diene units attached to N-heterocycles

• Franca M. Cordero,
• Carolina Vurchio,
• Stefano Cicchi,
• Armin de Meijere and
• Alberto Brandi

Beilstein J. Org. Chem. 2011, 7, 298–303, doi:10.3762/bjoc.7.39

• Göttingen, Tammannstrasse 2, 37077 Göttingen, Germany 10.3762/bjoc.7.39 Abstract Dienes embedded in quinolizidine and indolizidine structures can be prepared in four steps from cyclic nitrones and bicyclopropylidene. The key intermediates α-spirocyclopropanated N-heterocyclic ketones, generated via a

• domino 1,3-dipolar cycloaddition/thermal rearrangement sequence, were converted by Wittig methylenation to the corresponding vinylcyclopropanes (VCPs), which underwent rearrangement to 1,3-dienes in the presence of the Wilkinson Rh(I) complex under microwave heating. The previously unexplored Rh(I

• )-catalyzed opening of the VCP moiety embedded in an azapolycyclic system occurs at high temperature (110–130 °C) to afford the corresponding 1,3-dienes in moderate yield (34–53%). Keywords: nitrogen heterocycles; rearrangement; rhodium; small ring systems; spiro compounds; Introduction The cyclopropyl

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

• Cedric Fischmeister Christian Bruneau UMR 6226-CNRS-Université de Rennes 1, Sciences Chimiques de Rennes, Catalyse et Organométalliques, Campus de Beaulieu, 263 avenue du général Leclerc, 35042 Rennes cedex, France 10.3762/bjoc.7.22 Abstract Conjugated 1,3-dienes are important building blocks in

• with ruthenium catalysts was initiated in 1997 when Mori [39] and Blechert [40] reported the first examples with ethylene and higher olefins, respectively. EYCM with ethylene The EYCM with ethylene is one of the simplest methods to generate conjugated dienes with two terminal methylene groups from

• synthesis of Anolignans [48] and another closely related example is shown in the preparation of Amphidinolide E [50][51] where the diene system is extended by further cross-metathesis with 2-methylpenta-1,4-diene (Figure 2). The Diels–Alder reaction is one of the most popular transformations of 1,3-dienes

Tandem catalysis of ring-closing metathesis/atom transfer radical reactions with homobimetallic ruthenium–arene complexes

• Yannick Borguet,
• Xavier Sauvage,
• Guillermo Zaragoza,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2010, 6, 1167–1173, doi:10.3762/bjoc.6.133

• , during the course of our investigations on the RCM of various α,ω-dienes catalyzed by complex 1, 31P NMR monitoring of the reaction media always showed a rapid disappearance of the signal originating from this precatalyst, and its replacement by a new singlet at ca. 40.5 ppm due to the ethylene complex 2

• demonstrated that homobimetallic ruthenium–indenylidene complex 1 is a suitable catalyst precursor for the tandem RCM/ATRC of polyhalogenated α,ω-dienes 4 and 8 into the corresponding bicyclic γ-lactam derivatives. A more complex cascade sequence involving RCM and ATRA reactions afforded γ-lactone 18 starting

New library of aminosulfonyl-tagged Hoveyda–Grubbs type complexes: Synthesis, kinetic studies and activity in olefin metathesis transformations

• Etienne Borré,
• Frederic Caijo,
• Christophe Crévisy and
• Marc Mauduit

Beilstein J. Org. Chem. 2010, 6, 1159–1166, doi:10.3762/bjoc.6.132

• catalysts was investigated with various substrates in ring-closing metathesis of dienes or enynes and cross metathesis. The results demonstrate that these catalysts show a good tolerance to various chemical functions. Keywords: cross-metathesis; kinetic studies; olefin metathesis; RCM; ruthenium

• weak influence on the behaviour of the catalysts in these cases. Finally, the reactivity profiles of 4a and 4g were compared in various metathesis reactions in order to evaluate the influence of the NHC ligand. The last point of our study was the comparison between catalysts in RCM of dienes or enynes

About the activity and selectivity of less well-known metathesis catalysts during ADMET polymerizations

• Hatice Mutlu,
• Lucas Montero de Espinosa,
• Oĝuz Türünç and
• Michael A. R. Meier

Beilstein J. Org. Chem. 2010, 6, 1149–1158, doi:10.3762/bjoc.6.131

• catalytic activities in RCM of linear dienes [32][34][35] and ROMP of cycloolefins [36][37][38][39][40] were reported. RCM studies with diethyl diallylmalonate and diallyl tosylamine as substrates showed an appreciable catalytic activity and selectivity for the 2nd generation 16-electron Ru–indenylidene

Synthesis of oxa-bridged derivatives from Diels–Alder bis-adducts of butadiene and 1,2,3,4-tetrahalo-5,5-dimethoxycyclopentadiene

• Faiz Ahmed Khan and
• Karuppasamy Parasuraman

Beilstein J. Org. Chem. 2010, 6, No. 64, doi:10.3762/bjoc.6.64

• reactions. We and other groups have demonstrated the utility of cyclic dienes for the synthesis of 2:1 Diels–Alder bis-adducts with 1,2,3,4-tetrahalo-5,5-dimethoxycyclopentadiene 1 [4][5][6][7]. In the case of cyclic dienes (or trienes) such as cyclohexa-1,4-diene and cycloheptatriene, endo-syn-endo

• -adducts of 1 with cyclic dienes. Diels–Alder reaction of 1a with 3-sulfolene. Synthesis of bis-oxa-bridged compounds 8 and 10 from bis-adducts 5 and 6. Diels–Alder reaction of 1b with 3-sulfolene. Synthesis of bis-oxa-bridged compounds 8 and 10 from bis-diketones 14 and 15. Supporting Information

Synthesis of fluorinated δ-lactams via cycloisomerization of gem-difluoropropargyl amides

• Satoru Arimitsu and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2010, 6, No. 48, doi:10.3762/bjoc.6.48

• some bioactive compounds [23][24][25]. Dienes 2a and 2b were used in Diels–Alder reactions with 4 and 6 to produce 5 and 4,4-difluoroisoquinolin-3-one derivatives 7, respectively, in excellent yield and good stereoselectivity (Scheme 1). Phenyl-substituted diene 2c gave no reaction, even after a longer

Novel loop-like aromatic compounds: a further step on the road to nanobelts and nanotubes

• Venkataramana Rajuri,
• Dariush Ajami,
• Gaston R. Schaller,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2010, 6, No. 30, doi:10.3762/bjoc.6.30

• the most electron deficient dienes used in Diels–Alder reactions and is readily accessible by the reaction of tetrachlorothiophene with peroxytrifluoroacetic acid [24][25]. The Diels–Alder reaction of 1 with an excess of diene 10, followed by instantaneous elimination of sulfur dioxide furnished

• and 7 using pyridazine, 1,2-bis(dibromomethyl)benzene and 2,3,4,5-tetrachlorothiophene-1,1-dioxide as dienes the loop-like molecules 2, 3, 5b, and 6 were obtained. All structures were verified by X-ray crystal structure analysis. ORTEP drawing of the crystal structures: a) 2 and b) 3. For additional

Fused bicyclic piperidines and dihydropyridines by dearomatising cyclisation of the enolates of nicotinyl-substituted esters and ketones

• Heloise Brice,
• Jonathan Clayden and
• Stuart D. Hamilton

Beilstein J. Org. Chem. 2010, 6, No. 22, doi:10.3762/bjoc.6.22

• mixture of dienes 11 gave ester 12 after hydrogenation (Scheme 4). It proved challenging to isolate cleanly the silyl ketene acetal derived from 12, so instead we decided to form and cyclise the silyl derivative in a single pot. Thus, ester 12 was added to LDA at −78 °C, and the enolate quenched with

Solvent-free phase-vanishing reactions with PTFE (Teflon^®) as a phase screen

• Kevin Pels and
• Veljko Dragojlovic

Beilstein J. Org. Chem. 2009, 5, No. 75, doi:10.3762/bjoc.5.75

• and either acrylic acid or dimethyl fumarate react at a relatively high rate [26]. As most Diels-Alder reactions are relatively slow, and most dienes are highly reactive towards halogens, it may be necessary to carry out sequential reactions. Solvent-free PV-PTFE reaction design is simple and

Preparation and Diels–Alder/cross coupling reactions of a 2-diethanolaminoboron- substituted 1,3-diene

• Liqiong Wang,
• Cynthia S. Day,
• Marcus W. Wright and
• Mark E. Welker

Beilstein J. Org. Chem. 2009, 5, No. 45, doi:10.3762/bjoc.5.45

• substituted dienes are stable but their organic solvent solubility is not ideal. Preparation of more highly substituted BF3 dienes also requires a transmetallation protocol which yields a Grignard-BF3 by-product which has to be separated from the desired diene [9]. To overcome these methodology challenges we

• have begun to prepare diethanolaminoboron substituted dienes and we communicate our first results in this area here. Results and Discussion The diethanolamine boronyl substituted diene 2 was obtained as white needles on a several gram scale from a simple procedure which involved preparing the Grignard

• than the BF3 substituted diene. In the solid state (Figure 1, see Supporting Information), C(1)–C(2) and C(2)–C(3) bond lengths were virtually identical in both dienes whereas B–C(2) (1.609(5) Å vs 1.576(13) Å) and C(3)–C(4) (1.308(6) Å vs 1.279(13) Å) were significantly longer in the diethanolamine