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

• ]. Synthesis of alkenols 20-23 and 30. Reagents and conditions: a) lit. [31] (COCl)2, DMSO, Et3N, CH2Cl2, −78 °C to rt, 2 h; b) Phosphonium salt, BuLi, THF, 0 °C to rt, overnight, MPLC; c) lit. [32] (EtO)2POCH2CO2Et, NaH, THF, 0 °C to rt, 3 h; d) 60% AcOH, 60 °C, 3 h; e) MeMgCl, Et2O, 0 °C to rt, 1 h; f) Dess

Facile synthesis of 1-alkoxy-1H-benzo- and 7-azabenzotriazoles from peptide coupling agents, mechanistic studies, and synthetic applications

• Mahesh K. Lakshman,
• Manish K. Singh,
• Mukesh Kumar,
• Raghu Ram Chamala,
• Vijayender R. Yedulla,
• Domenick Wagner,
• Evan Leung,
• Lijia Yang,
• Asha Matin and
• Sadia Ahmad

Beilstein J. Org. Chem. 2014, 10, 1919–1932, doi:10.3762/bjoc.10.200

• demonstrated the isolation and synthetic utility of a nucleoside phosphonium salt [28]. Thus, to us the reaction of oximes with BOP was an intriguing result, leading us to query whether a benzotriazolyl intermediate, rather than a phosphonium ion, was formed en route to the cyanide. This line of reasoning

Rasta resin–triphenylphosphine oxides and their use as recyclable heterogeneous reagent precursors in halogenation reactions

• Xuanshu Xia and
• Patrick H. Toy

Beilstein J. Org. Chem. 2014, 10, 1397–1405, doi:10.3762/bjoc.10.143

• reagents and catalysts [27][28][29][30][31][32][33], and have used easily synthesized rasta resin–Ph3P (14) in various Wittig reactions that required only filtration and solvent removal for product purification (Figure 1) [27][28][29]. Additionally, 14 was converted into phosphonium salt 15, which proved

Deoxygenative gem-difluoroolefination of carbonyl compounds with (chlorodifluoromethyl)trimethylsilane and triphenylphosphine

• Fei Wang,
• Lingchun Li,
• Chuanfa Ni and
• Jinbo Hu

Beilstein J. Org. Chem. 2014, 10, 344–351, doi:10.3762/bjoc.10.32

• difluoromethylene phosphonium ylide, which can be generated in situ either by the transformation of a difluorinated phosphonium salt or by the reaction between difluorocarbene (:CF2) and a phosphine (Scheme 1) [19][20][21][22][23][24][25][26]. In 1964, Fuqua and co-workers first reported the difluoromethylenation

• of aldehydes by using ClCF2CO2Na/PPh3 [19]. In 1967, Burton and Herkes suggested that the ylide intermediate involved in the olefination process was more likely to be formed by the decarboxylation of a difluorinated phosphonium salt rather than the combination of :CF2 and a phosphine (Scheme 1

• ). As determined by 19F NMR, besides the side product (difluoromethyl)triphenylphosponium bromide (δ −127.9, dd, 3JP-F = 80 Hz, 2JF-H = 47 Hz) as reported in the Wittig olefination with FSO2CF2CO2Me [25], a new product which was assigned as difluorinated phosphonium salt 4 (δ −88.8, ddd, 2JF-F = 298 Hz

Cyclic phosphonium ionic liquids

• Sharon I. Lall-Ramnarine,
• Joshua A. Mukhlall,
• James F. Wishart,
• Robert R. Engel,
• Alicia R. Romeo,
• Masao Gohdo,
• Sharon Ramati,
• Marc Berman and
• Sophia N. Suarez

Beilstein J. Org. Chem. 2014, 10, 271–275, doi:10.3762/bjoc.10.22

• thermal properties of the phosphonium ILs 5a–d and their ammonium congeners are given in Table 1. Comparison of the five-membered cyclic cation ILs C4mPphol NTf2 5a and C4mPyrr NTf2 (butylmethylpyrrolidinium NTf2) reveals that the viscosity of the phosphonium salt is one third higher than that of the

Total synthesis of the endogenous inflammation resolving lipid resolvin D2 using a common lynchpin

• John Li,
• May May Leong,
• Alastair Stewart and
• Mark A. Rizzacasa

Beilstein J. Org. Chem. 2013, 9, 2762–2766, doi:10.3762/bjoc.9.310

• Abstract The total synthesis of the endogenous inflammation resolving eicosanoid resolvin D2 (1) is described. The key steps involved a Wittig reaction between aldehyde 5 and the ylide derived from phosphonium salt 6 to give enyne 17 and condensation of the same ylide with aldehyde 7 to afford enyne 11

• using the common linchpin phosphorus ylide derived from phosphonium salt 6 [21][22] and each of the homochiral aldehydes 5 and 7 [9]. Synthesis of vinyl iodide 4 The synthesis of fragment 4 began with the production of the aldehyde 7 as shown in Scheme 2. A Wittig reaction between hemiacetal 8 [23] and

• the ylide derived from 9 provided the alkene 10 [9] with excellent stereoselectivity. Oxidation of 10 with Dess–Martin periodinane then afforded aldehyde 7. The phosphonium salt 6 [21][22] was produced from propargyl bromide via silylation of the derived sodium salt with TIPSCl followed by reaction

Garner’s aldehyde as a versatile intermediate in the synthesis of enantiopure natural products

• Mikko Passiniemi and
• Ari M.P. Koskinen

Beilstein J. Org. Chem. 2013, 9, 2641–2659, doi:10.3762/bjoc.9.300

• the dehydrohalogenation of the phosphonium salt [103]. These complexes react with carbonyl compounds differently. Addition reactions of other ylides to 1, proceeded with little or no racemization of 1. The E/Z-ratio of the reaction was 1:13 favouring the Z-adduct 66. In comparison to Beaulieu’s

An organocatalytic route to 2-heteroarylmethylene decorated N-arylpyrroles

• Alexandre Jean,
• Jérôme Blanchet,
• Jacques Rouden,
• Jacques Maddaluno and
• Michaël De Paolis

Beilstein J. Org. Chem. 2013, 9, 1480–1486, doi:10.3762/bjoc.9.168

• to form imines 2b,c. Hence, when imines 2b,c were exposed to aldehyde 1a in the presence of catalyst 6 (available in racemic form), the Mannich adducts 7i,j were obtained and directly reacted with phosphonium salt 3. In line with our procedure, the resulting acyclic anilines 8i,j were then exposed to

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

• 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

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

• 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

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

• acetonitrile gave phosphonium salts 7a–7c and 7e. Starting from 4-chlorophenylacetic acid, 4-chlorophenethyl bromide (8) was prepared in 78% overall yield according to the literature method [48] (Scheme 9). The phosphonium salt 7c, an intermediate to dibromide 1c, was prepared starting from the known 2-(trans

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