Hydroquinone–pyrrole dyads with varied linkers

• Hao Huang,
• Christoffer Karlsson,
• Maria Strømme,
• Martin Sjödin and
• Adolf Gogoll

Beilstein J. Org. Chem. 2016, 12, 89–96, doi:10.3762/bjoc.12.10

• material, a Wittig reaction was chosen as an alternative. The Wittig reaction approach is shown in Scheme 2. In this reaction, phosphonium salt 7 was prepared in quantitative yield from 5 and triphenylphosphine by reflux in toluene, according to a procedure reported for dimethoxybenzyl chloride [21]. The

• expected to have different electronic properties. After desilylation, compound 3c was obtained in a combined total yield of 35% (sum of cis-3c and trans-3c) from the pyrrole-3-carbaldehyde. To obtain trans-4c selectively, a Wittig–Horner reaction was investigated, with dimethoxybenzyl bromide as starting

Catalytic asymmetric formal synthesis of beraprost

• Yusuke Kobayashi,
• Ryuta Kuramoto and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2015, 11, 2654–2660, doi:10.3762/bjoc.11.285

• could be readily prepared from ortho-bromophenol (9, Scheme 2). O-Allylation of 9 followed by Lewis acid-mediated Claisen rearrangement afforded ortho-allylphenol 11, whose olefin moiety was ozonolyzed and subsequently treated with Wittig reagent 13 to provide amide 7 in 55% yield over four steps from 9

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

• . Reductive desulfonylation and a final Wittig olefination of the ketone then afforded racemic β-caryophyllene (22). In summary, the total synthesis of β-caryophyllene was achieved in 19 steps with an overall yield of 6.3%. Although the key intramolecular acyl transfer reaction for construction of the

• . The ester group was selectively reduced and desilylation afforded alcohol 84. The generated primary alcohol was tosylated and regioselective deprotonation followed by intramolecular α-alkylation stereoselectively formed the cyclobutane ring. A final Wittig methylenation introduced the exocyclic double

• proceed via the chair-like transition state 104, afforded key intermediate 105 with high diastereo- and enantioselectivity. Preparation of the δ-lactone 106 of the A ring of xeniolide F was then realized by treatment of Claisen product 105 with the methylene Wittig reagent, followed by desilylation and

Synthesis of α,β-unsaturated esters via a chemo-enzymatic chain elongation approach by combining carboxylic acid reduction and Wittig reaction

• Yitao Duan,
• Peiyuan Yao,
• Yuncheng Du,
• Jinhui Feng,
• Qiaqing Wu and
• Dunming Zhu

Beilstein J. Org. Chem. 2015, 11, 2245–2251, doi:10.3762/bjoc.11.243

• chain elongation approach to access α,β-unsaturated esters by combining an enzymatic carboxylic acid reduction and Wittig reaction. Recently, we have found that Mycobacterium sp. was able to reduce phenylacetic acid (1a) to 2-phenyl-1-ethanol (1c) and two sequences in the Mycobacterium sp. genome had

• aromatic and aliphatic carboxylic acids, including ibuprofen. The Mycobacterium CAR catalyzed carboxylic acid reduction to give aldehydes, followed by a Wittig reaction to afford the products α,β-unsaturated esters with extension of two carbon atoms, demonstrating a new chemo-enzymatic method for the

• synthesis of these important compounds. Keywords: α,β-unsaturated esters; carboxylic acid reductase; chemoenzymatic synthesis; reduction; Wittig reaction; Introduction α,β-Unsaturated esters are versatile building blocks for organic synthesis and of significant importance for industrial applications [1][2

A new approach to ferrocene derived alkenes via copper-catalyzed olefination

• Vasily M. Muzalevskiy,
• Aleksei V. Shastin,
• Alexandra D. Demidovich,
• Namiq G. Shikhaliev,
• Abel M. Magerramov,
• Victor N. Khrustalev,
• Rustem D. Rakhimov,
• Sergey Z. Vatsadze and
• Valentine G. Nenajdenko

Beilstein J. Org. Chem. 2015, 11, 2072–2078, doi:10.3762/bjoc.11.223

• methods for the preparation of ethynylferrocenes [24][25][26][27][28][29]. In most cases, the key reagents for the synthesis of ethynylferrocene are the corresponding mono- and dihalogenvinylferrocene derivatives. These compounds are generally prepared using a variation of the Wittig reaction (the Corey

Lewis acid-promoted hydrofluorination of alkynyl sulfides to generate α-fluorovinyl thioethers

• Davide Bello and
• David O'Hagan

Beilstein J. Org. Chem. 2015, 11, 1902–1909, doi:10.3762/bjoc.11.205

• Several methods for the synthesis of vinyl thioethers have been reported, including Wittig reactions [8], ionic and radical additions of thiols to alkynes [9] and coupling of 1-alkenyl halides with thiols, among others [10][11]. However, the literature for the preparation of α-fluorovinyl thioethers is

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• the fruiting body of P. igniarius, is a well-known anticancer agent. To assemble the spiro-fused furanone core of phelligridin G, Wright and Cooper [55] have used a RRM process as a key step. Wittig olefination of furylbenzaldehyde derivative 265 using methyltriphenylphosphonium bromide in the

• presence of n-BuLi provided styrylfuran 270 in 72% yield. The DA reaction of styrene derivative 270 with DMAD 129 at 40 °C yielded oxabridged compound 268. Another route to 268 involves a DA reaction of 265 with DMAD at 55 °C for longer reaction time (3 days) and sequential Wittig olefination. The spiro

Preparation of conjugated dienoates with Bestmann ylide: Towards the synthesis of zampanolide and dactylolide using a facile linchpin approach

• Jingjing Wang,
• Samuel Z. Y. Ting and
• Joanne E. Harvey

Beilstein J. Org. Chem. 2015, 11, 1815–1822, doi:10.3762/bjoc.11.197

• ylide to this versatile and readily obtained reagent [6][7][8]. Studies revealed that the ylide readily reacts with alcohols and amines to form α-phosphoranylidene esters or amides, providing diverse isolable Wittig reagents that can be used in subsequent transformations [4][5][9][10][11]. Furthermore

• , if the α-phosphoranylidene ester or amide is formed in the presence of an aldehyde, ketone or ester, an additional in situ Wittig reaction can occur [12][13][14][15][16][17][18]. In this way, amides, esters and thioesters can be obtained through three-component couplings [14][16]. Intramolecular

• and Michael addition, followed by a Wittig reaction [19][20]. Although the utility of the Bestmann ylide in the synthesis of acyclic α,β-unsaturated esters and dienamides has already been reported [11][13][16], its application to the synthesis of α,β,γ,δ-unsaturated esters (i.e., dienoates) remains

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

• vinyl β-C-deoxyribofuranoside was based on transformation of 6-O-tert-butyldiphenylsilyl-3,5-dideoxy-5-iodo-L-lyxo-hexofuranose [14]. A reaction sequence relying on Horner–Wadsworth–Emmons/ring closure–halogenation/Ramberg–Bäcklund/Wittig reaction gave rise to the equimolar mixture of styryl α- and β-C

Synthesis of γ-hydroxypropyl P-chirogenic (±)-phosphorus oxide derivatives by regioselective ring-opening of oxaphospholane 2-oxide precursors

• Iris Binyamin,
• Shoval Meidan-Shani and
• Nissan Ashkenazi

Beilstein J. Org. Chem. 2015, 11, 1332–1339, doi:10.3762/bjoc.11.143

• ; oxaphospholanes; phosphinates; phosphine oxides; Introduction Organophosphorus compounds containing phosphorus to carbon bond(s) are widely used in organic transformations. Textbook examples are the Wittig and the Horner–Wadsworth–Emmons reactions. Moreover, the vast majority of ligands used in organometallic

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

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

• particular the distortions associated with the bulky tert-butyl groups. For all these hydrocarbons, di-tert-butylketone (1) served as the starting material, which was chain-elongated by preparative sequences involving standard Wittig, Wittig–Horner and McMurry coupling reactions. Nearly all of the polyenes 2

Reactions of nitroxides 15. Cinnamates bearing a nitroxyl moiety synthesized using a Mizoroki–Heck cross-coupling reaction

• Jerzy Zakrzewski and
• Bogumiła Huras

Beilstein J. Org. Chem. 2015, 11, 1155–1162, doi:10.3762/bjoc.11.130

• Toxicology (in the 70s). The most recent reviews in this series were published in 2011 [10][11]. Cinnamic acid derivatives can be synthesized using Perkin, Knoevenagel, Claisen [7], and Wittig [12] condensation reactions. Since the discovery of catalytic coupling reactions, cinnamic derivatives have also

Direct access to pyrido/pyrrolo[2,1-b]quinazolin-9(1H)-ones through silver-mediated intramolecular alkyne hydroamination reactions

• Hengshuai Wang,
• Shengchao Jiao,
• Kerong Chen,
• Xu Zhang,
• Linxiang Zhao,
• Dan Liu,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2015, 11, 416–424, doi:10.3762/bjoc.11.47

• -insertion reaction [7], the cycloaddition of anthranilic acid iminoketene to a methyl butyrolactam through a sulfinamide anhydride intermediate [9], the intramolecular aza-Wittig reaction with an azide substrate [10], and the cycloaddition of anthranilamide [11]. For the synthesis of vasicinone (5

Attempts to prepare an all-carbon indigoid system

• Şeref Yildizhan,
• Henning Hopf and
• Peter G. Jones

Beilstein J. Org. Chem. 2015, 11, 363–372, doi:10.3762/bjoc.11.42

• , and then oxidizing the presumably resulting carbanion to 21 (a known compound [19]) with Cu(OTf)2, which gave cleaner results than the chloride employed previously. Unfortunately, all efforts to convert 21 into 4 failed. Thus neither the Wittig reaction of 21 (MeP(Ph)3Br/n-BuLi, THF) nor its treatment

• that caused all these preparative difficulties, we next decided to investigate the behavior of diketone 19, in which this conjugation is interrupted. Although its methylenation under Wittig conditions was again unsuccessful, the reaction with the Tebbe’s reagent provided a product. This, however, was

Electrochemical selenium- and iodonium-initiated cyclisation of hydroxy-functionalised 1,4-dienes

• Philipp Röse,
• Steffen Emge,
• Jun-ichi Yoshida and
• Gerhard Hilt

Beilstein J. Org. Chem. 2015, 11, 174–183, doi:10.3762/bjoc.11.18

• adopt a Z-configuration. Accordingly, the products of type 2 are formed in high selectivity in terms of regio- and diastereomeric control. The starting materials of type 1 were generated from the aromatic aldehydes and allyltriphenylphosphonium bromide in a Wittig reaction following a known protocol [53

NAA-modified DNA oligonucleotides with zwitterionic backbones: stereoselective synthesis of A–T phosphoramidite building blocks

• Boris Schmidtgall,
• Claudia Höbartner and
• Christian Ducho

Beilstein J. Org. Chem. 2015, 11, 50–60, doi:10.3762/bjoc.11.8

• synthesis of both 6'-epimers of nucleosyl amino acid 9 has been reported before. We have used 3-(N-BOM)-protected thymidine-5'-aldehyde 10 (BOM = benzyloxymethyl), which can readily be obtained from thymidine, in a sequence of Wittig–Horner reaction, asymmetric hydrogenation of the resultant didehydro

• corresponding uridine-derived nucleosyl amino acids, we have found that uracil protection was not advantageous for the aforementioned reaction sequence [48]. We have therefore decided to employ both the 3-(N-BOM)-protected thymidine-5'-aldehyde 10 and also its thymine-unprotected congener 11 in Wittig–Horner

• stability, thymidine-5'-aldehydes 10 and 11 were not stored, but directly used for the subsequent Wittig–Horner reaction. They were therefore converted with glycine-derived phosphonate 12 [51][52][53][54] in the presence of potassium tert-butoxide as a base. As anticipated [47][48][55], these reactions

Formal total syntheses of classic natural product target molecules via palladium-catalyzed enantioselective alkylation

• Yiyang Liu,
• Marc Liniger,
• Ryan M. McFadden,
• Jenny L. Roizen,
• Jacquie Malette,
• Corey M. Reeves,
• Douglas C. Behenna,
• Masaki Seto,
• Jimin Kim,
• Justin T. Mohr,
• Scott C. Virgil and
• Brian M. Stoltz

Beilstein J. Org. Chem. 2014, 10, 2501–2512, doi:10.3762/bjoc.10.261

• was crossed with methyl vinyl ketone in 62% yield [34]. Reduction of enone 34 was achieved in the presence of Pd/C with H2 in EtOAc to furnish diketone 35 [34]. Chemoselective Wittig mono-olefination of 35 provided ω-enone (−)-32, spectroscopically identical to the material in Danishefsky’s racemic

Indium-mediated allylation in carbohydrate synthesis: A short and efficient approach towards higher 2-acetamido-2-deoxy sugars

• Christopher Albler,
• Ralph Hollaus,
• Hanspeter Kählig and
• Walther Schmid

Beilstein J. Org. Chem. 2014, 10, 2230–2234, doi:10.3762/bjoc.10.231

• makes use of readily accessible pentoses and hexoses, which are subjected to indium-mediated two-carbon chain elongation. Subsequent ozonolysis and treatment with base yields α,β-unsaturated aldehydes, which are stereoselectively epoxidized using Jørgenson’s protocol. After Wittig chain elongation the

• decomposition of these labile compounds. Conversion of the carbonyl moiety to an acetal group followed by treatment with azide nucleophiles also failed to yield any desired products. Therefore we decided to mask the aldehyde as an olefin. A Wittig reaction with methyl (triphenylphosphoranylidene)acetate (Ph3P

Photochemical approach to functionalized benzobicyclo[3.2.1]octene structures via fused oxazoline derivatives from 4- and 5-(o-vinylstyryl)oxazoles

• Ivana Šagud,
• Simona Božić,
• Željko Marinić and
• Marija Šindler-Kulyk

Beilstein J. Org. Chem. 2014, 10, 2222–2229, doi:10.3762/bjoc.10.230

• .10.230 Abstract Novel cis/trans-4- and cis/trans-5-(2-vinylstyryl)oxazoles have been synthesized by Wittig reactions from the diphosphonium salt of α,α’-o-xylene dibromide, formaldehyde and 4- and 5-oxazolecarbaldehydes, respectively. In contrast, trans-5-(2-vinylstyryl)oxazole has been synthesized by

• /trans-Isomers of 4- and 5-oxazole derivatives (1, 2) were synthesized by Wittig reactions from the diphosphonium salt of α,α’-o-xylene dibromide, formaldehyde and oxazole-4- and 5-carbaldehydes (3, 4), respectively, in absolute ethanol with sodium ethoxide as a base (Scheme 1). The procedure of this

• isocyanide (TosMIC) [38][39]. For the preparation of 5-(2-vinylstyryl)oxazole (2) by this method 3-(2-vinylphenyl)acrylaldehyde (6) was needed. This new o-substituted phenylacrylaldehyde 6 was prepared using (formylmethylene)triphenylphosphorane by a Wittig reaction from o-vinylbenzaldehyde (5). The yield of

Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

• enantioselectivity. In a relatively successful example, the chiral aminophosphine G9 catalyzed the asymmetric double-Michael reaction between o-tosylamidophenyl malonate and 3-butyn-2-one to give the indoline derivative in 69% yield and up to 10% ee (Scheme 53). 2.15 Annulation through tandem Michael addition/Wittig

• olefination In 2009, Tang and Zhou developed an annulation through tandem Michael addition/Wittig olefination, mediated by the chiral phosphine BIPHEP, for the synthesis of optically active cyclohexa-1,3-diene derivatives (Scheme 54) [97]. Although this reaction required a stoichiometric amount of chiral

Palladium-catalysed cyclisation of alkenols: Synthesis of oxaheterocycles as core intermediates of natural compounds

• Miroslav Palík,
• Jozef Kožíšek,
• Peter Koóš and
• Tibor Gracza

Beilstein J. Org. Chem. 2014, 10, 2077–2086, doi:10.3762/bjoc.10.216

• –Wadsworth–Emmons olefination of aldehyde 15 furnished the corresponding separable mixture of Z and E alkenes 16 and 17. In the case of utilising stabilised phosphorane ylides, the Wittig reaction provided only Z alkenes 18 and 19. Following acidic hydrolysis provided α-O-benzyl substrates 20–23 in good

• yields. Additionally, the synthesis of substrate 30 with 1,1-disubstituted C–C double bond was accomplished in 3 steps. The addition of methylmagnesium chloride to previously prepared threose 15, followed by Dess–Martin oxidation of the secondary alcohol gave methylketone 29. Subsequent Wittig

Five-membered ring annelation in [2.2]paracyclophanes by aldol condensation

• Henning Hopf,
• Swaminathan Vijay Narayanan and
• Peter G. Jones

Beilstein J. Org. Chem. 2014, 10, 2021–2026, doi:10.3762/bjoc.10.210

• compounds 2 we previously prepared precursors such as 5 (easily available by Wittig–Horner reaction of the appropriate bis-formyl cyclophanes) and subjected them to catalytic hydrogenation followed by a double Friedel–Crafts cyclization. However, it appeared to us that a more direct route to these useful

Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules

• Thilo Focken and
• Stephen Hanessian

Beilstein J. Org. Chem. 2014, 10, 1848–1877, doi:10.3762/bjoc.10.195

• ‘typical’ Wittig and Horner–Wadsworth–Emmons reagents were screened. In addition, cyclic phosphonamides were utilized as olefination reagents (Table 1). Employing phosphonamides 24e and 77 in the olefination of 72 favored the formation of the desired E-isomer of 73a, however the mixture of isomers was

• sequence as shown in Scheme 10. Replacing phosphonamide 79 with Wittig-reagent 80 as olefinating reagent gave a separable E/Z mixture in a ratio of 1:9 in favor of the desired Z-isomer of 73b (Table 1, entry 5). The latter was then transformed into Z-9 in an analogous fashion as described for the E-isomer

• ]. Kishi and co-workers adopted a convergent approach to fumonisin B2, with the molecule being cleaved into three main fragments 103–105 [45][46]. The connection of 103 and 104 under formation of the fumonisin backbone would employ a Wittig reaction, followed by attachment of two molecules of

Multicomponent reactions in nucleoside chemistry

• Mariola Koszytkowska-Stawińska and
• Włodzimierz Buchowicz

Beilstein J. Org. Chem. 2014, 10, 1706–1732, doi:10.3762/bjoc.10.179

• group has developed the synthesis of D-glucopyranose-derived counterparts of compounds 25 and 26 [73]. The formation of an intermediate imine from a sugar azide and an aldehyde by Staudinger/aza-Wittig reaction was the key step of the synthesis. 2. The Kabachnik–Fields reaction The Kabachnik–Fields