(Pseudo)amide-linked oligosaccharide mimetics: molecular recognition and supramolecular properties

• José L. Jiménez Blanco,
• Fernando Ortega-Caballero,
• Carmen Ortiz Mellet and
• José M. García Fernández

Beilstein J. Org. Chem. 2010, 6, No. 20, doi:10.3762/bjoc.6.20

• carbodiimides via a tandem Staudinger-aza-Wittig type reaction with triphenylphosphine and an isothiocyanate, followed by the addition of a nucleophile (H2O, H2S, NH3, amines) (Figure 14). Although this second methodology is more straightforward and versatile than the first, only a few examples of

Enantioselective synthesis of tricyclic amino acid derivatives based on a rigid 4-azatricyclo[5.2.1.0^2,6]decane skeleton

• Matthias Breuning,
• Tobias Häuser,
• Christian Mehler,
• Christian Däschlein,
• Carsten Strohmann,
• Andreas Oechsner and
• Holger Braunschweig

Beilstein J. Org. Chem. 2009, 5, No. 81, doi:10.3762/bjoc.5.81

• oxidation of the alkene rac-13 (Scheme 3), which was available from the ketone rac-9 either by Wittig reaction or by a Tebbe-type olefination [31] using Mg, TiCl4, and CH2Cl2. Hydroboration/oxidation of rac-13 occurred highly diastereoselectively on the exo-side providing the desired endo-alcohol rac-14, as

• , and thus proximity-facilitated tandem hydride transfer/cyclization sequence [33]. Since the yields of rac-15 from the alkene rac-13 were low, we turned our attention to an alternative approach via the enol ether 18, which was available from 9 as a 1:1 mixture of E/Z-isomers by Wittig reaction with

• 12% yield from 9). The preparation of the amino acid 8a•HCl and the N-tosylamide 8b•HCl required the attachment of an endo-oriented acetic acid substituent at the position of the keto group in 9 (Scheme 5). Initial attempts to introduce such a side chain by Wittig or Horner-Wadsworth-Emmons reactions

Ring strain and total syntheses of modified macrocycles of the isoplagiochin type

• Andreas Speicher,
• Timo Backes,
• Kerstin Hesidens and
• Jürgen Kolz

Beilstein J. Org. Chem. 2009, 5, No. 71, doi:10.3762/bjoc.5.71

• moiety (see 7), from which a Z double bond (for 5) or an E double bond may be obtainable by Lindlar-type hydrogenation and (for 6) by subsequent Z → E isomerization (Scheme 2). The final ring closure using a McMurry protocol (probably more rigorous for ring-strained frameworks than the Wittig-protocol in

• boronic acid 22 with the bromoarene 16 under carefully optimized conditions followed by acidic workup afforded the hydroxyaldehyde 27 as precursor for cyclization (Scheme 6). A cyclization protocol for the intramolecular Wittig reaction, well established [15][20] for the synthesis of the tetramethyl ether

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

Green oxidations: Titanium dioxide induced tandem oxidation coupling reactions

• Vineet Jeena and
• Ross S. Robinson

Beilstein J. Org. Chem. 2009, 5, No. 24, doi:10.3762/bjoc.5.24

• to extend the methodology, a preliminary investigation into a titanium dioxide mediated tandem Wittig reaction was attempted in which the intermediate aldehyde is trapped by a stabilised phosphorane. Unfortunately, NMR spectroscopic analysis revealed a multitude of peaks, none of which were

An expedient synthesis of 5-n-alkylresorcinols and novel 5-n-alkylresorcinol haptens

• Kirsti Parikka and
• Kristiina Wähälä

Beilstein J. Org. Chem. 2009, 5, No. 22, doi:10.3762/bjoc.5.22

• Helsinki, Finland 10.3762/bjoc.5.22 Abstract The first synthesis of bioactive long alkyl chain 5-n-alkylresorcinols, present in whole grain products, by a novel modification of the Wittig reaction is described. All the main long chain 5-n-alkylresorcinols present in rye and wheat, including C23 and C25

• way for the immunochemical detection techniques of alkylresorcinols. Keywords: 5-n-alkylresorcinols; haptens; microwave assisted synthesis; Wittig reaction; Introduction 5-Alk(en)ylresorcinols and related compounds are phenolic lipids present in several families of plants (e.g. Gramineae

• -dimethoxybenzaldehyde (18–48% yields whenever reported) [22][23][24][25][26]. Additional synthetic methods have been developed for shorter chain AR (Wittig approach utilises the ozonolysis product of a pentadecylresorcinol (C15

Reversible intramolecular photocycloaddition of a bis(9-anthrylbutadienyl)paracyclophane – an inverse photochromic system. (Photoactive cyclophanes 5)

• Henning Hopf,
• Christian Beck,
• Jean-Pierre Desvergne,
• Henri Bouas-Laurent,
• Peter G. Jones and
• Ludger Ernst

Beilstein J. Org. Chem. 2009, 5, No. 20, doi:10.3762/bjoc.5.20

• structure and photochromic properties of 2 are reported in this paper. Results and Discussion 1 Synthesis Compound 2 was prepared from dialdehyde 3 using the Wittig reaction, as outlined in Scheme 1, in 48% yield. Dialdehyde 3 wasobtained in five steps from [2.2]paracylophane, a commercial product, in 72

• % overall yield as described previously [19]. Therefore, the overall yield of 2 from the parent cyclophane was found tobe 35% on the gram scale. The Wittig reaction provides a mixture of cis and trans isomers, but the pure all-trans isomer was isolated by crystallization as orange crystals (see Experimental

• structure of 4 (1,4 : 2′,3′-cycloadduct). Preparation of 2 (last step), using the Wittig reaction. The preparation of 3 has been described in ref [19]. Angles between various partial planes in molecule 2 in the crystal. Supporting Information Supporting Information File 40: Thermal dissociation of

Convenient methods for preparing π-conjugated linkers as building blocks for modular chemistry

• Jiří Kulhánek,
• Filip Bureš and
• Miroslav Ludwig

Beilstein J. Org. Chem. 2009, 5, No. 11, doi:10.3762/bjoc.5.11

• and 4-bromobenzyl(triphenyl)phosphonium bromide [37] by the Wittig reaction [37][38] in 37 and 54% yields, respectively. In contrast to the Horner–Wadsworth–Emmons reaction, this procedure afforded both (E)- and (Z)-stilbenes that were isomerized by heating with traces of iodine in toluene to afford

Synthesis and redox behavior of new ferrocene- π-extended- dithiafulvalenes: An approach for anticipated organic conductors

• Abdelwareth A. O. Sarhan,
• Omar F. Mohammed and
• Taeko Izumi

Beilstein J. Org. Chem. 2009, 5, No. 6, doi:10.3762/bjoc.5.6

• the modified Wittig–Horner cross-coupling reaction using n-BuLi/THF at temperature varies from −78 °C to 0 °C. These new classes of bis(1,3-dithiafulvalene)ferrocenes have the 1,3-dithiole ring system separated by ferrocene as conjugated spacer. The ferrocene-dithiafulvalenes derivatives 9 and 12 were

• these systems [27]. Results and Discussion In this work we synthesized a series of novel 1,1′-bis[(1,3-dithiol-2-ylidene)heteroaryl/aryl]ferrocene [1,1′-bis(1,3-DTF)Fc] derivatives as new electron donor compounds using the direct Wittig–Horner cross coupling reaction. The starting 1,1′-diacylferrocene

• ′-diacetylferrocene (5b) with 1,3-benzodithiole-2-phosphonate (6) in dry THF in the presence of n-BuLi at −78 °C following the Wittig–Horner reaction method afforded the corresponding 1,1′-bis[(1,3-dithiol-2-ylidene)methyl]ferrocenes 7a and 7b in good yields (Scheme 1). The 1,1′-bis(1,3-dithiafulvalene)ferrocene 7a

Catalytic synthesis of (E)-α,β-unsaturated esters from aldehydes and 1,1-diethoxyethylene

• Rubén Manzano,
• Lidia Ozores,
• Andreas Job,
• Lars Rodefeld and
• Benjamin List

Beilstein J. Org. Chem. 2009, 5, No. 3, doi:10.3762/bjoc.5.3

• high yielding synthesis of α,β-unsaturated esters from aldehydes and 1,1-diethoxyethylene was developed. Keywords: 1,1-diethoxyethylene; α,β-unsaturated esters; Introduction A number of reactions transforming aldehydes into α,β-unsaturated esters have been developed and especially Wittig reaction

• variants are widely used [1]. A general problem with these approaches, however, is their unsatisfactory atom economy resulting in significant by-product formation (Scheme 1, eq 1–2). Alternatives have been suggested but a solution that is both as general and efficient as the Wittig procedures and

A facile synthesis and fungicidal activities of 2-(alkylamino)-5,6-dimethylthieno[2,3-d]pyrimidin- 4(3H)-ones

• Yang-Gen Hu,
• Ai-Hua Zheng,
• Xu-Zhi Ruan and
• Ming-Wu Ding

Beilstein J. Org. Chem. 2008, 4, No. 49, doi:10.3762/bjoc.4.49

• Education, Central China Normal University, Wuhan 430079, China 10.3762/bjoc.4.49 Abstract The aza-Wittig reactions of iminophosphorane 3 with aromatic isocyanates generated carbodiimides 4, which were reacted with alkylamines under mild conditions to give a series of 2-(alkylamino)-5,6-dimethylthieno[2,3

• activities against six kinds of fungi. Keywords: 2-(alkylamino)-5,6-dimethylthieno[2,3-d]pyrimidin-4(3H)-one; aza-Wittig reaction; fungicidal activity; synthesis; Introduction Over the past ten years, aza-Wittig reactions of functionalized iminophosphoranes with isocyanates have been applied to produce

• interested in the synthesis of a series of new heterocyclic compounds via aza-Wittig reaction of α- or β-(ethoxycarbonyl)-substituted iminophosphoranes with aromatic isocyanates and subsequent reaction with various nucleophiles under mild conditions [11][12][13][14]. Herein we wish to report an efficient

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

• utilizing Wu’s own methodology. Wittig reaction of the aldehyde 37 and the Wittig reagent 38 furnished the butenolide unit 39. The tetrahydrofuran part of 22 was constructed from D-glucose via epoxide 40. The entire carbon skeleton of 41 was constructed by Pd(0)-catalyzed cross-coupling reaction between 39

• building block 45 by means of the Sharpless AD reaction and cyclization catalyzed by Co(modp)2 (the Mukaiyama epoxidation method) under mild reaction conditions. The connection of the THF unit 46 with the γ-lactone segment 47 was carried out by means of a Wittig reaction. The target compound 42 had

• conditions resulted in a smooth conversion of the starting material into THF 89. Triol (+)-90 was obtained with lipase Amano AK desymmetrization. For the appropriate side chain attachment, the termini were differentiated to give lactone (−)-91. Reduction of (−)-91 followed by a Wittig reaction yielded fully

End game strategies towards the total synthesis of vibsanin E, 3-hydroxyvibsanin E, furanovibsanin A, and 3-O-methylfuranovibsanin A

• Brett D. Schwartz,
• Craig M. Williams and
• Paul V. Bernhardt

Beilstein J. Org. Chem. 2008, 4, No. 34, doi:10.3762/bjoc.4.34

• lithium aluminium hydride proceded smoothly, however, global oxidation caused significant problems yielding only very low amounts of aldehyde 52, which was not enough to attempt the Wittig reaction with 45 (Scheme 8). In the view of the diasppointing results obtained above (Scheme 8) all attention was

• . Installation of the furan ring system continued. Installation of the enol sidechain utilizing Wittig chemistry. Attempts to gain access to targets 50 and 51. Further attempts to gain access to target compound 51. Supporting Information Supporting Information File 9: Experimental Supporting Information File 10

Flexible synthesis of poison- frog alkaloids of the 5,8-disubstituted indolizidine- class. II: Synthesis of (-)-209B, (-)-231C, (-)-233D, (-)-235B", (-)-221I, and an epimer of 193E and pharmacological effects at neuronal nicotinic acetylcholine receptors

• Soushi Kobayashi,
• Naoki Toyooka,
• Dejun Zhou,
• Hiroshi Tsuneki,
• Tsutomu Wada,
• Toshiyasu Sasaoka,
• Hideki Sakai,
• Hideo Nemoto,
• H. Martin Garraffo,
• Thomas F. Spande and
• John W. Daly

Beilstein J. Org. Chem. 2007, 3, No. 30, doi:10.1186/1860-5397-3-30

• (-)-231C, (-)-221I and (-)-epi-193E on α4β2 and α7 nicotinic receptors, the most abundant subtypes in the mammalian brain. [4] Results and Discussion Reduction of the lactam 1 [1] with LiAlH4 followed by Swern oxidation of the resulting alcohol and Wittig reaction gave the olefin 3 in 78% overall yield

• (Scheme 1). Hydrogenation of the double bond in 3 with 10% Pd/C provided (-)-209B, whose spectral data were identical with reported values. [7] The lactam 1 was also converted to the alcohol 4, [1] which was transformed into (-)-235B" by Swern oxidation followed by Wittig reaction under high dilution and

• 'salt free' conditions (Scheme 1). The spectral data of synthetic (-)-235B" were identical with reported values. [8][9] Indolizidines (-)-231C [10] and (-)-233D [10] were synthesized from common intermediate 5 prepared from the alcohol 4. Thus, the Swern oxidation of 4 and then the Wittig reaction of

Flexible synthetic routes to poison- frog alkaloids of the 5,8-disubstituted indolizidine- class I: synthesis of common lactam chiral building blocks and application to the synthesis of (-)-203A, (-)-205A, and (-)-219F

• Naoki Toyooka,
• Dejun Zhou,
• Hideo Nemoto,
• H. Martin Garraffo,
• Thomas F. Spande and
• John W. Daly

Beilstein J. Org. Chem. 2007, 3, No. 29, doi:10.1186/1860-5397-3-29

• , followed by an Arndt-Eistert sequence of the resulting carboxylic acid. Reduction of both carbonyl groups in 14 with lithium aluminum hydride provided the alcohol, which was directly used for formation of Z-iodoolefin 15. Thus, the Dess-Martin periodinane oxidation [24] of the alcohol, followed by Wittig

• , CHCl3)) suggest that the absolute stereochemistry of natural 203A is 5S, 8R, 9S. We achieved the total synthesis of (-)-205A starting from 1 via 13 (Scheme 3). Lithium aluminum hydride reduction of 13 followed by Swern oxidation and Wittig reaction of the resulting aldehyde gave the olefin 17

An efficient synthesis of tetramic acid derivatives with extended conjugation from L-Ascorbic Acid

• Biswajit K. Singh,
• Surendra S. Bisht and
• Rama P. Tripathi

Beilstein J. Org. Chem. 2006, 2, No. 24, doi:10.1186/1860-5397-2-24

• aldehydes. Wittig olefination followed by reaction of the resulting tetranolactonyl dienyl esters with different amines resulted in the respective 5-hydroxy lactams. Subsequent dehydration of the hydroxy lactams with p-toluene sulphonic acid afforded the dienyl tetramic acid derivatives. All reactions were

• compounds were determined on the basis of their spectroscopic data (Supporting Information File 1). Wittig olefination of aldehydes 7 and 8 with carbethoxymethylene triphenylphosphorane in THF at ambient temperature led to the formation of the respective exo-dienyl esters of the tetronolactones as a mixture

• studies. In such an earlier study, [37] with BuLi at -78°C used as the base for the Wittig olefination, lower yields and poor stereoselection was observed as compared to our uncatalysed ambient temperature reaction where ZZ isomers were predominantly formed. The Z configuration of the allylic alcohol was

Total syntheses of oxygenated brazanquinones via regioselective homologous anionic Fries rearrangement of benzylic O-carbamates

• Glaucia Barbosa Candido Alves Slana,
• Mariângela Soares de Azevedo,
• Rosângela Sabattini Capella Lopes,
• Cláudio Cerqueira Lopes and
• Jari Nobrega Cardoso

Beilstein J. Org. Chem. 2006, 2, No. 1, doi:10.1186/1860-5397-2-1

• metalation groups (DMGs) undergo competitive anionic [1,2] and [1,4] Wittig – carbamoyl rearrangements (paths a and b) [18][19] orientated by the groups R and DMGs (Figure 1). Conceptual combination of path b and the well established tandem DoM route to anthraquinones and heteroanthraquinones [20] led to the

• conjecture that, barring the competitive [1,2]–Wittig rearrangement, and one-pot route, 3 → 4 → 1, may be established in a direct manner without resort to DoM-derived benzamide intermediate, thereby establishing new carbonyl dianion equivalency 4 (see Scheme 1). We now report the versatility of this strategy

New modification of the Perkow reaction: halocarboxylate anions as leaving groups in 3-acyloxyquinoline- 2,4(1H,3H)-dione compounds

• Oldřich Paleta,
• Karel Pomeisl,
• Stanislav Kafka,
• Antonín Klásek and
• Vladislav Kubelka

Beilstein J. Org. Chem. 2005, 1, No. 17, doi:10.1186/1860-5397-1-17

• out[3] (product 2) via the intramolecular Wittig synthesis using a bromoacetyl derivative of the starting 3-hydroxyquinolinediones (1, Scheme 1). Unlike haloalkanes and halocycloalkanes that undergo nucleophilic substitution reaction with trialkyl phosphites to afford the corresponding phosphonates

• reaction. Conversely, the 3-acetoxyquinoline-2,4(1H,3H)-diones bearing acetoxy group react via a different pathway. The annulation resulting in the formation of the targeted product 10 was successfully carried out[3] by the intramolecular Wittig synthesis using the bromoacetyl derivative of the starting 3

Synthesis of highly substituted allenylsilanes by alkylidenation of silylketenes

• Stephen P. Marsden and
• Pascal C. Ducept

Beilstein J. Org. Chem. 2005, 1, No. 5, doi:10.1186/1860-5397-1-5

• be used as a handle for further synthetic elaboration. Amongst the myriad methods to prepare allenylsilanes,[1][14] an attractive disconnection is to consider a Wittig-type alkylidenation of a silylketene, Figure 1. This convergent approach potentially allows for tremendous variation in substitution

• pattern at both termini of the allenylsilane, yet has been little exploited thus far. Ruden first demonstrated that the stabilised phosphorane carbethoxymethylenetriphenylphosphorane underwent Wittig condensation with trimethylsilylketene at sub-ambient temperature in high yield, but found that non