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

• be generated by double deprotonation of β-hydroxy primary phosphonium salts [10][11][12][13][14][15][16][17][18][19], where the latter are obtained from Ph3P and 1,2-halohydrins [10][11][12][13][14][15][16][19] or (in the presence of acid) from terminal epoxides [17][18]. In seeking a more concise

• access ylides [26], although phosphonium ylides for carbonyl-olefination chemistry are usually prepared by deprotonation of phosphonium salts [1][2][3][4]. In fact, phosphine trapping of lithium carbenoids followed by carbonyl olefination has been little studied since Seyferth and Wittig independently

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

• conjugate addition to 1, with generation of a tributylphosphonium salt (δ = +37 ppm) of the probable zwitterionic structure 5 (Scheme 3; for the 31P NMR spectrum see the Supporting Information File 1). Similar phosphonium phenolates are known to exist either as the zwitterionic (analogue to 5) or neutral

• phosphorane structure (analogue to 5’) [43][44]. Under the conditions of the catalytic reaction, phosphonium (+37 ppm) was the only species of importance and thus represents the resting state of the catalytic reaction, which could be either 5 or 6. We did not observe a 31P NMR signal for n-Bu3P, or a signal

• the catalyst n-Bu3P present will be converted to a water-soluble phosphonium salt, which is easier to separate from the coumarin product than the neutral phosphane is. Second, the yields of coumarins were higher when the quenching procedure was used. This implies that part of the coumarin product may

Synthesis of trifunctional cyclo-β-tripeptide templates

• Frank Stein,
• Tahir Mehmood,
• Tilman Plass,
• Javid H. Zaidi and
• Ulf Diederichsen

Beilstein J. Org. Chem. 2012, 8, 1576–1583, doi:10.3762/bjoc.8.180

• mg, 92.5 µmol, 5.00 equiv), bromo-tris-pyrrolidino phosphonium hexafluorophosphate (PyBrOP) (43.2 mg, 92.6 µmol, 5.01 equiv) and DIEA (32.2 µL, 185 µmol, 10.0 equiv) were added. After stirring of the reaction mixture for 72 h, the solvent was removed under reduced pressure and the crude title

Metal–ligand multiple bonds as frustrated Lewis pairs for C–H functionalization

• Matthew T. Whited

Beilstein J. Org. Chem. 2012, 8, 1554–1563, doi:10.3762/bjoc.8.177

• electron-deficient Lewis acid. In the case where molecular hydrogen interacts with a phosphine/borane FLP, this occurs by the formation of a phosphonium/borate ion pair (Scheme 1). For unsaturated substrates, the reaction is better described as an insertion or cycloaddition (see Scheme 2 for a

A quantitative approach to nucleophilic organocatalysis

• Herbert Mayr,
• Sami Lakhdar,
• Biplab Maji and
• Armin R. Ofial

Beilstein J. Org. Chem. 2012, 8, 1458–1478, doi:10.3762/bjoc.8.166

• photonucleofuges [38][39][40][41], the stable iminium salts 3-PF6 were treated with tertiary phosphines 10 at room temperature to give the enamino-phosphonium ions 11 instantaneously (Figure 4a). Their irradiation with 7 ns laser pulses (266 nm) regenerated the iminium ions, the decay of which was monitored

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

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

• A the reaction is thought to proceed through the simple ion pair 3 formed by the reaction of one equivalent of triphenylphosphine (1) and one equivalent of carbon tetrabromide (2). This can react with the alcohol substrate to form an oxy-phosphonium 4 along with bromoform (5), which is removed under

• reduced pressure at the end of the reaction along with the solvent. The oxy-phosphonium salt 4 then reacts with the bromide counterion to produce the substituted product 6 along with the triphenylphosphine oxide byproduct (7). However, 3 is in equilibrium with the inverted ion pair 8, which can proceed

• via pathway B in which 8 reacts with a second equivalent of triphenylphosphine to form the dibromophosphorane 9 and phosphorane 10. This dibromophosphorane 9 is then able to react with an alcohol to give intermediate 4, which can proceed to the product, whereas 10 proceeds to a phosphonium salt

Coupled chemo(enzymatic) reactions in continuous flow

• Ruslan Yuryev,
• Simon Strompen and
• Andreas Liese

Beilstein J. Org. Chem. 2011, 7, 1449–1467, doi:10.3762/bjoc.7.169

• columns connected in parallel were filled with polymer-supported hydroxybenzotriazole, and during the process they worked either in loading or in elution mode. In the loading mode the columns were flushed with a solution of 49, bromo-tris-pyrrolidino-phosphonium hexafluorophosphate (PyBrOP) and

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• conducted in phosphonium salt-based ionic liquids (PSILs) with PdCl2(PPh3)2/CuI/DBU as the catalyst system [30]. In this case, the palladium-mediated Sonogashira coupling reaction leading to 1-halo-2-alkynylbenzene derivatives is followed by a carboxyamidation in the presence of carbon monoxide and primary

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

• -heptylidenetriphenylphosphonium bromide in the presence of n-BuLi gave adduct 11 as an (E/Z)-mixture (E/Z = 1:5) in 75% yield. Selective removal of the TBS group with pyridinium tosylate gave 12 in 98% yield [21]. With the alcohol 12 in hand, our next step was to synthesize the phosphonium salt 15 [22][23] (Scheme 4). Therefore

• , ε-caprolactone was hydrolyzed with 5% NaOH to give hydroxy acid 13 in quantitative yield, which was reacted with PBr3 in CH2Cl2 to afford compound 14 in 82% yield. Treatment of 14 with PPh3 in CH3CN gave the phosphonium salt 15 in 98% yield. The construction of the aliphatic chain was achieved

The preparation of 3-substituted-1,5-dibromopentanes as precursors to heteracyclohexanes

• Bryan Ringstrand,
• Martin Oltmanns,
• Jeffrey A. Batt,
• Aleksandra Jankowiak,
• Richard P. Denicola and
• Piotr Kaszynski

Beilstein J. Org. Chem. 2011, 7, 386–393, doi:10.3762/bjoc.7.49

• conditions with a phosphonium salt [23]. Piperidines III (Y = H) can undergo degradation to form dibromides I although this process is typically less efficient [12][14][15]. The piperidine ring can be reconstituted by ring-closure of I with an appropriate amine or aniline Y–NH2 [2][22]. The thianes IV are

• from diols 2a and 2b or tetrahydropyrans 3a–3d (Scheme 3). When H2SO4 was used instead of the phosphonium salt, the yield of 1b was lower (67%). The dibromides were purified on silica gel and, in addition, 1a and 1b were distilled. Preparation of diols Diols 2a and 2b, containing simple alkyl chains

• using standard conditions by reacting phosphonium salts 7a–7c and 7e with either BuLi in anhydrous THF, or NaHMDS in a 1:1 mixture of anhydrous Et2O and anhydrous CH2Cl2. Heating the corresponding alkyl halide (Br or I) with PPh3 under reflux in concentrated solutions of toluene, benzene, or

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

Synthesis of indolo[3,2-b]carbazole-based new colorimetric receptor for anions: A unique color change for fluoride ions

• Ajit Kumar Mahapatra,
• Giridhari Hazra and
• Prithidipa Sahoo

Beilstein J. Org. Chem. 2010, 6, No. 12, doi:10.3762/bjoc.6.12

• ][24][25][26][27][28], there is a paucity of reports on selective naked-eye chemosensors for fluoride [29][30][31]. Nitrophenyl, nitronaphthalene urea [32][33][34], naphthalene triphenyl-phosphonium [35], benzimidazolyl pyridine [36][37] and oxidized bis(indolyl)methane [38] as signal units for

1-(4-Alkyloxybenzyl)-3-methyl-1H-imidazol-3-ium organic backbone: A versatile smectogenic moiety

• William Dobbs,
• Laurent Douce and
• Benoît Heinrich

Beilstein J. Org. Chem. 2009, 5, No. 62, doi:10.3762/bjoc.5.62

• the cations and anions the physico-chemical properties of ionic liquids can be tuned and specifically optimised for a wide range of applications [5][6][7][8][9][10][11]. Although many organic cations (e.g. phosphonium, ammonium, pyridinium, imidazolium) can be used for the design of ionic liquids

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

• water solubility more generally, aryl modified phosphonium salts, carrying a –COOH group [38] or PEG attachments [39], have been developed but require extensive synthetic work. Previously, non-stabilized alkylphosphonium salts have appeared much less amenable than the benzyl analogues. A single paper

• MW catalyzed synthesis route where 3,5-dimethoxy benzaldehyde and unstabilized alkyltriphenyl phosphonium ylids react in DMSO/H2O works as well and alkylresorcinol precursors that do not have a commercially available alkanal starting material can be synthesized rapidly and efficiently by way of this

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

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

• -ascorbic acid was elongated by two carbons to give ester 50 using a four-step sequence, the protected diol of which was then treated with H5IO6 to give the chiral aldehyde 51. On the other hand, 49 was converted to phosphonium salt 52, which was treated with aldehyde 51, and the resulting alkene was

• trilobacin (169) (ED50 <10−15 µg/mL) was over 1 billion times more potent against HT-29 than adriamycin (ED50 = 6.69 × 10−3 µg/mL) [71][72]. In 1996, Sinha’s group [73] reported the first total synthesis of 169 (Scheme 24). The phosphonium salt 172 and aldehyde 175 were prepared using the AD reaction from

• both the linear and the convergent strategies, synthetic efficiency and diversity. The phosphonium salt 279, which was synthesized from 274, was reacted with aldehyde 280 in a Wittig reaction, which, after global deprotection, allowed completion of the total synthesis of asimicin (260). The spectral

Synthesis of 2,6-trans- disubstituted 5,6-dihydropyrans from (Z)-1,5-syn-endiols

• Eric M. Flamme and
• William R. Roush

Beilstein J. Org. Chem. 2005, 1, No. 7, doi:10.1186/1860-5397-1-7

• /1860-5397-1-7 Abstract Certain (Z)-1,5-syn-diols 2 may be converted into 2,6-trans-5,6-dihydropyrans by using phosphonium salt 4 or phosphorane 5 as dehydrating agents. A more general four step procedure converts the (Z)-1,5-syn-endiols into enantiomeric dihydropyrans ent-3 via regioselective

• . In order to avoid the presence of nucleophilic counter ions, we turned to the use of phosphonium salt 4 and phosphorane 5 as the cyclodehydration reagents (Scheme 2).[24][25] Treatment of diol 2a with 4 in acetonitrile (0.05 M) at 0°C and warming slowly to 23°C provided a 9 : 1 mixture of trans and

• cyclodehydration of 2b with phosphorane 5 in toluene at 80°C proceeded with ca. 9 : 1 regioselectivity (entry 4), and use of the phosphonium salt 4 at -35°C also gave reasonably good results (84% e.e.). However, all attempts to dehdyrate the α,α'-oxygenated diol 7 with either 4 or 5 were unsuccessful. Given that