Amyloid-β probes: Review of structure–activity and brain-kinetics relationships

• Todd J. Eckroat,
• Abdelrahman S. Mayhoub and
• Sylvie Garneau-Tsodikova

Beilstein J. Org. Chem. 2013, 9, 1012–1044, doi:10.3762/bjoc.9.116

• ]. Benzofurans Replacement of the nitrogen of the benzoxazole backbone with carbon affords the benzofuran backbone of compounds 121–126 (Figure 4), which has also been successfully employed for radioimaging of Aβ plaques. The [11C]-labeled benzofuran 121 was prepared via Wittig reaction between the

• group in place of the N,N-dimethylaminopyridine group, was prepared using a Wittig reaction between the triphenylphosphonium salt of 2-hydroxy-5-methoxybenzyl alcohol (127) and 4-dimethylaminobenzoyl chloride (35), followed by O-demethylation and installation of the [18F]-labeled linker (Scheme 9C

Direct alkenylation of indolin-2-ones by 6-aryl-4-methylthio-2H-pyran-2-one-3-carbonitriles: a novel approach

• Sandeep Kumar,
• Ramendra Pratap,
• Abhinav Kumar,
• Brijesh Kumar,
• Vishnu K. Tandon and
• Vishnu Ji Ram

Beilstein J. Org. Chem. 2013, 9, 809–817, doi:10.3762/bjoc.9.92

• group as well as by Wittig reaction [23][24]. The growing importance of 3-alkenylindolin-2-ones has resulted in the design of numerous new synthetic routes. Recently, metal-catalyzed carbonylative annulation of alkynyl-arylamines has been employed for the synthesis of this class of compounds [25][26][27

Facile synthesis of benzothiadiazine 1,1-dioxides, a precursor of RSV inhibitors, by tandem amidation/intramolecular aza-Wittig reaction

• Krishna C. Majumdar and
• Sintu Ganai

Beilstein J. Org. Chem. 2013, 9, 503–509, doi:10.3762/bjoc.9.54

• -dioxides through an intramolecular aza-Wittig reaction. The reaction was found to be general through the synthesis of a number of benzothiadiazine 1,1-dioxides. Acid-catalyzed hydrolysis of 3-ethoxy-1,2,4-benzothiadiazine 1,1-dioxides furnished the 2-substituted benzothiadiazine-3-one 1,1-dioxides in good

• yields and high purity, which is the core moiety of RSV inhibitors. Keywords: benzothiadiazine-3-one 1,1-dioxide; 3-ethoxy-1,2,4-benzothiadiazine 1,1-dioxide; intramolecular aza-Wittig reaction; sultam; Introduction Sultams have gained popularity in the scientific community especially among synthetic

• derivatives have been reported [25][26][27][28][29][30][31][32], the development of a simpler method for the synthesis of the 1,2,4-benzothiadiazine 1,1-dioxide moiety is still desirable because of their biological significance. The aza-Wittig reaction is employed for the construction of C=N, N=N and S=N

A new synthetic protocol for coumarin amino acid

• Xinyi Xu,
• Xiaosong Hu and
• Jiangyun Wang

Beilstein J. Org. Chem. 2013, 9, 254–259, doi:10.3762/bjoc.9.30

• will further improve the fluorescent property of the coumarin amino acids, or add new chemical handles to the coumarin ring for some specific investigations. The Horner–Wadsworth–Emmons reaction was applied to install the terminal alkene at the 4-position. Compared with the Wittig reaction, the Horner

• –Wadsworth–Emmons reaction has a significant advantage: The resulting phosphate byproduct can be readily separated, whereas the byproduct triphenylphosphine oxide generated in the Wittig reaction is difficult to remove [17]. The effect of the base used in the Horner–Wadsworth–Emmons reaction on the reaction

Alkenes from β-lithiooxyphosphonium ylides generated by trapping α-lithiated terminal epoxides with triphenylphosphine

• David. M. Hodgson and
• Rosanne S. D. Persaud

Beilstein J. Org. Chem. 2012, 8, 1896–1900, doi:10.3762/bjoc.8.219

• with high regio- and stereocontrol (Scheme 1) [1][2][3][4][5][6][7][8][9]. These ylide intermediates can be generated by initiating a Wittig reaction between an aldehyde 1 and a phosphorane 2 at low temperature in the presence of lithium salts, which promote ring opening of the initially formed

A Wittig-olefination–Claisen-rearrangement approach to the 3-methylquinoline-4-carbaldehyde synthesis

• Mukund G. Kulkarni,
• Mayur P. Desai,
• Deekshaputra R. Birhade,
• Yunus B. Shaikh,
• Ajit N. Dhatrak and
• Ramesh Gannimani

Beilstein J. Org. Chem. 2012, 8, 1725–1729, doi:10.3762/bjoc.8.197

• important 3-methylquinoline-4-carbaldehydes 6a–h from o-nitrobenzaldehydes 1a–h employing a Wittig-olefination–Claisen-rearrangement protocol. The Wittig reaction of o-nitrobenzaldehydes with crotyloxymethylene triphenylphosphorane afforded crotyl vinyl ethers 2a–h, which on heating under reflux in xylene

• % yield. General procedure for the Claisen rearrangement The crotyl vinyl ethers 2a–h (17 mmol) obtained from the Wittig reaction were dissolved in anhydrous xylene (35 mL) and the solution was heated under reflux for 5–7 h (TLC, ethyl acetate/petroleum ether 1:9). Then, the solvent was removed under

Cyclization of ortho-hydroxycinnamates to coumarins under mild conditions: A nucleophilic organocatalysis approach

• Florian Boeck,
• Max Blazejak,
• Markus R. Anneser and
• Lukas Hintermann

Beilstein J. Org. Chem. 2012, 8, 1630–1636, doi:10.3762/bjoc.8.186

• use of tri-n-butylphosphane (20 mol %) as a nucleophilic organocatalyst in MeOH solution allows cyclization to take place under much milder conditions (60–70 °C). Several coumarins were prepared, starting from ortho-hydroxyarylaldehydes, by Wittig reaction with Ph3P=CHCO2Me to (E)-methyl ortho

Parallel and four-step synthesis of natural-product-inspired scaffolds through modular assembly and divergent cyclization

• Hiroki Oguri,
• Haruki Mizoguchi,
• Hideaki Oikawa,
• Aki Ishiyama,
• Masato Iwatsuki,
• Kazuhiko Otoguro and
• Satoshi Ōmura

Beilstein J. Org. Chem. 2012, 8, 930–940, doi:10.3762/bjoc.8.105

• and 4 (Scheme 2), as reported previously [22]. Due to the instability of the corresponding amine building block bearing the indole unit, azide 27 was employed as a precursor. Staudinger/aza-Wittig reaction [43] of 27 and 20 and subsequent condensation with 6 and 21 afforded the peptidyl product 28

Two-directional synthesis as a tool for diversity-oriented synthesis: Synthesis of alkaloid scaffolds

• Kieron M. G. O’Connell,
• Monica Díaz-Gavilán,
• Warren R. J. D. Galloway and
• David R. Spring

Beilstein J. Org. Chem. 2012, 8, 850–860, doi:10.3762/bjoc.8.95

• EtOH and H2O under reflux to achieve ester saponification, which was followed by decarboxylation, proceeding smoothly to give the corresponding ketone in 76% yield. The ketone was then transformed to the exocyclic alkene 15 in 61% yield by Wittig reaction with the appropriate phosphonium salt. The

Dioxane dibromide mediated bromination of substituted coumarins under solvent-free conditions

• Subrata Kumar Chaudhuri,
• Sanchita Roy and
• Sanjay Bhar

Beilstein J. Org. Chem. 2012, 8, 323–329, doi:10.3762/bjoc.8.35

• [8], Et4N+Br− in the presence of hypervalent iodine reagents [9], and NBS in tetrabutylammonium bromide under molten salt conditions [10]. There is a recent report of the preparation of 3-bromocoumarins from acyclic precursors through bromination of a Wittig reagent with NBS followed by tandem Wittig

• reaction and cyclization [11]. Many of them involve high temperature, long reaction time, toxic, exotic and costly reagents, sometimes in excess to stoichiometric requirement, and organic solvents during and after the reactions. Thus, there is always an urgency to put ardent efforts towards the development

Synthesis of fused tricyclic amines unsubstituted at the ring-junction positions by a cascade condensation, cyclization, cycloaddition then decarbonylation strategy

• Iain Coldham,
• Adam J. M. Burrell,
• Hélène D. S. Guerrand,
• Luke Watson,
• Nathaniel G. Martin and
• Niall Oram

Beilstein J. Org. Chem. 2012, 8, 107–111, doi:10.3762/bjoc.8.11

• chemistry for the construction of the core ring system found in alkaloid natural products. Wittig reaction with aldehyde 16 should be possible to provide the core ring system found in the alkaloids meloscine and scandine [26][27][28][29][30]. However, we chose to investigate a shorter reaction sequence

• without the need for protecting groups and to carry out the Wittig reaction at an earlier stage, as shown in Scheme 6. Olefination of aldehyde 6 with the anion formed from methyltriphenylphosphonium bromide gave alkene 17, which was reduced with DIBAL-H to give aldehyde 18. Heating this aldehyde with

Photochemical and thermal intramolecular 1,3-dipolar cycloaddition reactions of new o-stilbene-methylene-3-sydnones and their synthesis

• Kristina Butković,
• Željko Marinić,
• Krešimir Molčanov,
• Biserka Kojić-Prodić and
• Marija Šindler-Kulyk

Beilstein J. Org. Chem. 2011, 7, 1663–1670, doi:10.3762/bjoc.7.196

• -cyanotoluene (see Supporting Information File 1 for full experimental data). Bromination of o-cyanotoluene afforded 2-(bromomethyl)benzonitrile (4) [24], which was transformed to triphenylphosphonium salt 5 [25] followed by Wittig reaction with 4-methylbenzaldehyde to 2-(4-methylstyryl)benzonitrile (6a,b) [26

The application of a monolithic triphenylphosphine reagent for conducting Appel reactions in flow microreactors

• Kimberley A. Roper,
• Heiko Lange,
• Anastasios Polyzos,
• Malcolm B. Berry,
• Ian R. Baxendale and
• Steven V. Ley

Beilstein J. Org. Chem. 2011, 7, 1648–1655, doi:10.3762/bjoc.7.194

• interest in using monolithic supports to facilitate key chemical transformations [20][21][22][23][24][25][26][27][28][29][30][31]. We recently reported on the development of a new monolithic triphenylphosphine reagent and its use in the Staudinger aza-Wittig reaction in flow [32][33]. Here we discuss the

A new phenylethyl alkyl amide from the Ambrostoma quadriimpressum Motschulsky

• Guolei Zhao,
• Chao Yang,
• Bing Li and
• Wujiong Xia

Beilstein J. Org. Chem. 2011, 7, 1342–1346, doi:10.3762/bjoc.7.158

• according to the synthetic plan shown in Scheme 5. Oxidation of the alcohol 12 with PCC afforded the corresponding aldehyde 16, followed by a Wittig reaction with salt 15 in the presence of two equiv LDA, which afforded the adduct 17 as an (E/Z)-mixture in 72% yield. The E/Z isomers of 17 were not separated

Toward an integrated route to the vernonia allenes and related sesquiterpenoids

• Da Xu,
• Michael A. Drahl and
• Lawrence J. Williams

Beilstein J. Org. Chem. 2011, 7, 937–943, doi:10.3762/bjoc.7.104

• the direct formation of 21 via bromomethyltriphenylphosphonium bromide (Scheme 4). This reaction was inefficient and gave both the (E)- and (Z)-bromoolefins as well as dibromoolefin 20. Bromo group scrambling under basic Wittig reaction conditions is known [63], and the usual procedure for Wittig

Construction of cyclic enones via gold-catalyzed oxygen transfer reactions

• Leping Liu,
• Bo Xu and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2011, 7, 606–614, doi:10.3762/bjoc.7.71

• oxygen transfer from a carbonyl group to a carbon–carbon triple bond, the so-called alkyne–carbonyl metathesis. This methodology has sparked the attention of the synthetic community, because it could serve as an efficient and atom-economic alternative to the Wittig reaction by the formation of a new

Application of the diastereoselective photodeconjugation of α,β-unsaturated esters to the synthesis of gymnastatin H

• Ludovic Raffier and
• Olivier Piva

Beilstein J. Org. Chem. 2011, 7, 151–155, doi:10.3762/bjoc.7.21

• configuration of the C-6 centre of the target molecule was controlled. Keywords: amide; diastereoselective protonation; dienol; isomerisation; Wittig reaction; Introduction The photodeconjugation of α,β-unsaturated esters 1 – which bear at least one hydrogen atom on γ-position – allows a straightforward

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

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

• 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

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

• reduced AR, the lack of stereochemical control was of no consequence. Following the Wittig reaction, catalytic hydrogenation and demethylation gave AR and AR haptens in ca. 40% overall yield. The Wittig product 7b was a practical starting material for the C23 hapten (2d), for which commercial alkanal or

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

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

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

• 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