N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• moiety (Scheme 13) [51]. Before conversion of the chloromethyl group into a phosphonium salt the chiral auxiliary was removed. The reaction of the ylide (R)-45 prepared from the chloride (R)-44 with benzaldehyde afforded (E)-alkene (S)-46 which after hydrogenation and basic hydrolysis gave ʟ

Superelectrophilic carbocations: preparation and reactions of a substrate with six ionizable groups

• Sean H. Kennedy,
• Makafui Gasonoo and
• Douglas A. Klumpp

Beilstein J. Org. Chem. 2019, 15, 1515–1520, doi:10.3762/bjoc.15.153

• (including methane) [6][7][8][9]. Numerous studies from our group and others have shown that relatively stable cationic centers – such as ammonium, phosphonium, and pyridinium groups – may also be part of superelectrophilic systems [10]. Recently, we described the chemistry of tri-, tetra-, and pentacationic

Introduction of an isoxazoline unit to the β-position of porphyrin via regioselective 1,3-dipolar cycloaddition reaction

• Xiujun Liu,
• Xiang Ma and
• Yaqing Feng

Beilstein J. Org. Chem. 2019, 15, 1434–1440, doi:10.3762/bjoc.15.143

• derivative TPP-CH2Cl. Notably, this intermediate was labile on silica-gel column to give the precursor hydroxymethylporphyrin. Hence recrystallization was employed to purify it. Later, refluxing of the solution of TPP-CH2Cl and PPh3 in toluene gave the phosphonium salt 1 [44]. To introduce the vinyl group at

• the β-position, a Wittig reaction was performed, in which the porphyrin phosphonium salt 1 reacted with 4-MeCO2-benzaldehyde in the presence of DBU to furnish the double bond, followed by insertion of Zn ions into the porphyrin cavity to give compound 2. Nitrile oxides [45] as one of the most reactive

• enantiomers of 3a is present, which assembled to a dimeric structure with the fifth chelation of a Zn2+ ion by the carbonyl group of the other molecule. The self-dimerization property of 3a may be utilized in supramolecular chemistry [50][51][52][53]. Experimental 1: Porphyrin phosphonium salt 1 was prepared

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• , 2-bromobenzaldehydes 62 and carbon monoxide (23) at atmospheric pressure, with the assistance of DABCO as base and tri(tert-butyl)phosphonium tetrafluoroborate as ligand (Scheme 19) [100]. A variety of substituents in the benzene rings (R1, R3) are compatible with the reaction conditions, but

Solid-phase synthesis of biaryl bicyclic peptides containing a 3-aryltyrosine or a 4-arylphenylalanine moiety

• Iteng Ng-Choi,
• Àngel Oliveras,
• Lidia Feliu and
• Marta Planas

Beilstein J. Org. Chem. 2019, 15, 761–768, doi:10.3762/bjoc.15.72

•  2) [30]. Subsequent macrolactamization was performed using O-(((1-cyano-2-ethoxy-2-oxoethylidene)amino)oxy)trispyrrilidin-1-yl)phosphonium hexafluorophosphate (PyOxim), Oxyma and DIPEA in N-methyl-2-pyrrolidone (NMP) for 24 h. The resulting resin was acidolytically cleaved and the crude reaction

Mechanistic studies of an L-proline-catalyzed pyridazine formation involving a Diels–Alder reaction with inverse electron demand

• Anne Schnell,
• J. Alexander Willms,
• S. Nozinovic and
• Marianne Engeser

Beilstein J. Org. Chem. 2019, 15, 30–43, doi:10.3762/bjoc.15.3

• deionized water within 2 h. The solution was stirred at room temperature for 24 h. The precipitated white solid was filtered off and washed with cold deionized water. TBCA was directly used for the synthesis of 9 without further treatment. Triphenyl[4-(6-phenyl-1,2,4,5-tetrazin-3-yl)benzyl]phosphonium

Anomeric modification of carbohydrates using the Mitsunobu reaction

• Julia Hain,
• Patrick Rollin,
• Werner Klaffke and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2018, 14, 1619–1636, doi:10.3762/bjoc.14.138

• . [26]. Assuming that the alcohol is sterically hindered and thus represents a relatively weak nucleophile, the deprotonated acidic partner, NuO−, can react with the phosphonium intermediate first to afford an intermediate Nu-O-PR’3. In the case where a carboxylic acid is used, Nu-O-PR’3 represents an

• . Likewise, standard alcohols are typically poor reaction partners in Mitsunobu glycosylations. Due to their high pKa values, the formation of the transient phosphonium betaine is hampered [43]. In an effort to overcome this drawback, several decades ago, Szarek et al. tested mercuric halides to assist the

Recyclable hypervalent-iodine-mediated solid-phase peptide synthesis and cyclic peptide synthesis

• Dan Liu,
• Ya-Li Guo,
• Jin Qu and
• Chi Zhang

Beilstein J. Org. Chem. 2018, 14, 1112–1119, doi:10.3762/bjoc.14.97

• amines in the presence of a coupling reagent is the most convenient and simplest way [1][2][3][4][5][6]. The most commonly used coupling reagents such as carbodiimide [7], phosphonium [8], and uronium salts [9] are efficient and commercially available. In spite of these merits of traditional coupling

Liquid-assisted grinding and ion pairing regulates percentage conversion and diastereoselectivity of the Wittig reaction under mechanochemical conditions

• Kendra Leahy Denlinger,
• Lianna Ortiz-Trankina,
• Preston Carr,
• Kingsley Benson,
• Daniel C. Waddell and
• James Mack

Beilstein J. Org. Chem. 2018, 14, 688–696, doi:10.3762/bjoc.14.57

• , and 5 indicates that the carbonate bases deprotonated the phosphonium salt to form the ylide which then subsequently added to the benzaldehyde. However, the oxygen anion could not bind to the phosphorus cation to produce the stilbene product, presumably due to the mismatched counter ion pair. After

• reacted and is bound to the polymer and thus less production of the desired phosphonium salt. As expected, only 8.5% unreacted 4-nitrobenzyl bromide was recovered when ethanol was used as a LAG solvent, demonstrating that ethanol is an effective LAG solvent for the production of the phosphonium salt

• (Table 5). Because the formation of the phosphonium salt is the first step of the Wittig reaction, the question arose whether performing the reaction stepwise could influence our ability to select for both percent conversion and diastereoselectivity. Using a stepwise reaction approach with ethanol as the

Progress in copper-catalyzed trifluoromethylation

• Guan-bao Li,
• Chao Zhang,
• Chun Song and
• Yu-dao Ma

Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11

• producing byproducts from a pentafluoroethylation. The proposed reaction mechanism is depicted in Scheme 9. First, a phosphonium ylide is formed after treating DFPB with DBU, and then dissociated to generate a difluorocarbene. The difluorocarbene reacts with DBU affording nitrogen ylide I, followed by a

Aminosugar-based immunomodulator lipid A: synthetic approaches

• Alla Zamyatina

Beilstein J. Org. Chem. 2018, 14, 25–53, doi:10.3762/bjoc.14.3

Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis

• Anna Kuźnik,
• Roman Mazurkiewicz and
• Beata Fryczkowska

Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269

• were not included in the above-mentioned review article. Increasing interest in phosphonium salts is also due to their use in drug design. It was demonstrated in the last decade that lipophilic cations having a triphenylphosphonium residue in the structure can be used as effective carriers of

• polymeric phosphonium salts that were amorphous and unable to crystallize. Such products may be formed as a result of a subsequent Michael-like addition of the starting phosphine to the initially obtained vinylphosphonium salt 1 (Scheme 3). The formation of the expected salt was faster than the side

• triphenylphosphine with 1-bromoethylbenzene. The resulting phosphonium salt 11 was then deprotonated to the corresponding ylide 12, which in the last step was subjected to bromination to give the expected α-bromoethylphosphonium bromide 13 [10]. 1.3. Peterson olefination of α-trimethylsilylphosphonium ylides with

Synthesis and photophysical properties of novel benzophospholo[3,2-b]indole derivatives

• Mio Matsumura,
• Mizuki Yamada,
• Atsuya Muranaka,
• Misae Kanai,
• Naoki Kakusawa,
• Daisuke Hashizume,
• Masanobu Uchiyama and
• Shuji Yasuike

Beilstein J. Org. Chem. 2017, 13, 2304–2309, doi:10.3762/bjoc.13.226

• benzophosphole-fused indole derivative and its various functionalized analogs such as the corresponding phosphine oxide, phosphonium salt, and borane–phosphine complex. Results and Discussion The synthesis of the parent tetracyclic molecule 10-phenyl-[1]benzophospholo[3,2-b]-N-methylindole (3), is shown in

• fluorescence properties with respect to the intensity. Complex 9 exhibited a high quantum yield (Ф = 75%), while complex 8 exhibited a weak emission (Ф = 11%). In these fluorescence spectra of compounds 4–7, a vibronic band was detected as a shoulder peak around 530 nm. In the case of phosphonium cation 7, the

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• Reaction Pecharsky and co-workers reported the solvent-free mechanochemical synthesis of phosphonium salts [54] and phosphorus ylides [55] in the presence of the weak base K2CO3. Mechanochemically prepared phosphorous ylide from triphenylphosphine in presence of K2CO3 was utilized for a one-pot solvent

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• ; thioetherification; Introduction In the 1960s and 1970s, the groups of Makosza, Starks, and Brändström pioneered the field of “phase transfer catalysis” by showing the beneficial effect of tetraalkyl-ammonium or -phosphonium salts to facilitate reactions between components that are present in two immiscible phases

• asymmetric applications. Besides quaternary ammonium salts, also chiral phosphonium salts [21][36], chiral (bis)guanidinium systems [22][27][37], chiral crown ethers [38][39], bifunctional onium salts [17][40][41][42][43][44][45][46], or even sulfonium salts [47][48] have been systematically developed very

• the first squaramide-containing chiral PTCs E, which also turned out to be very promising catalysts for the asymmetric α-fluorination of compounds 1 [44]. The groups of Ma and Cahard have intensively investigated the use of chiral spirocyclic phosphonium salts F as phase-transfer catalysts for

1-Imidoalkylphosphonium salts with modulated C_α–P⁺ bond strength: synthesis and application as new active α-imidoalkylating agents

• Jakub Adamek,
• Roman Mazurkiewicz,
• Anna Węgrzyk and
• Karol Erfurt

Beilstein J. Org. Chem. 2017, 13, 1446–1455, doi:10.3762/bjoc.13.142

• , crystalline phosphonium salts are new, powerful, and easy to use α-amidoalkylating agents, which are active either without the need for a catalyst or in the presence of organic bases (e.g., Hünig’s base) [20][21][22][23]. It is a well-known problem, that the reactivity of α-amidoalkylating agents toward

• )imide 7 with triarylphosphonium tetrafluoroborate was melted at 85–140 °C in the presence of NaBr as a catalyst under reduced pressure (0.1–0.2 mmHg) for 0.5–10 h (Table 2). Phthalimide-derived phosphonium salts 5 (A = o-C6H4) were usually obtained in good to excellent yields, whereas the yields of

• was isolated in 73% yield accompanied by only trace amounts of the expected phosphonium salt 5o (Table 2, last entry). It is assumed that both the extraordinary effective resonance stabilization of the imide anion and the excessive steric congestion in the transition state make the splitting of the Cα

Strategies toward protecting group-free glycosylation through selective activation of the anomeric center

• A. Michael Downey and
• Michal Hocek

Beilstein J. Org. Chem. 2017, 13, 1239–1279, doi:10.3762/bjoc.13.123

Decarboxylative and dehydrative coupling of dienoic acids and pentadienyl alcohols to form 1,3,6,8-tetraenes

• Ghina’a I. Abu Deiab,
• Mohammed H. Al-Huniti,
• I. F. Dempsey Hyatt,
• Emma E. Nagy,
• Kristen E. Gettys,
• Sommayah S. Sayed,
• Christine M. Joliat,
• Paige E. Daniel,
• Rupa M. Vummalaneni,
• Andrew T. Morehead Jr,
• Andrew L. Sargent and
• Mitchell P. Croatt

Beilstein J. Org. Chem. 2017, 13, 384–392, doi:10.3762/bjoc.13.41

• electrophilic terminal vinyl group of the pentadienyl ligand and the nucleophilic α-carbon are in close proximity to one another. Formation of the carbon–carbon bond would then regenerate the Pd(0) catalyst and phosphonium carboxylate D. Decarboxylative elimination of the phosphine results in formation the

First DMAP-mediated direct conversion of Morita–Baylis–Hillman alcohols into γ-ketoallylphosphonates: Synthesis of γ-aminoallylphosphonates

• Marwa Ayadi,
• Haitham Elleuch,
• Emmanuel Vrancken and
• Farhat Rezgui

Beilstein J. Org. Chem. 2016, 12, 2906–2915, doi:10.3762/bjoc.12.290

• second β’-conjugate addition of triethyl phosphite onto I (iii), followed by the release of DMAP would provide the phosphonium intermediate II (iv). Finally, the hydroxide ion is expected to react with II via an Arbuzov rearrangement to provide the desired γ-ketoallylphosphonate 2a (v) (Scheme 3). We

Catalytic Wittig and aza-Wittig reactions

• Zhiqi Lao and
• Patrick H. Toy

Beilstein J. Org. Chem. 2016, 12, 2577–2587, doi:10.3762/bjoc.12.253

• inexpensive reagents to generate the necessary phosphonium ylide (phosphorane) reactant (a phosphine, typically Ph3P (1), an alkyl halide and a base), also adds to its appeal [3][4]. However, despite its proven utility, the Wittig reaction suffers from limitations that may deter from its use, especially on a

• activated alkyl halides 4 and sodium carbonate to form the corresponding phosphonium ylides that reacted with aldehydes 6 to produce alkene products 7 and 22 as a byproduct. Subsequently they reported that the soluble organic base N,N-diisopropylethylamine was a good replacement for sodium carbonate in such

• reactions in that they also involve the reaction of a phosphonium ylide, in this case an iminophosphorane (or phosphinimide) such as 39, with a carbonyl group containing compound to form the carbon–nitrogen double bond of an imine along with a byproduct phosphine oxide such as 2 (Scheme 12). The difference

Enantioconvergent catalysis

• Justin T. Mohr,
• Jared T. Moore and
• Brian M. Stoltz

Beilstein J. Org. Chem. 2016, 12, 2038–2045, doi:10.3762/bjoc.12.192

• enantiopure phosphine catalyst 27 in order to generate the coupled product 30 with both high ee and dr (Scheme 6) [31]. Presumably, the allenyl stereochemistry is destroyed upon 1,4-addition of the phosphine catalyst, resulting in chiral phosphonium adduct 29 that further reacts with deprotonated oxazole 28

• . The resulting intermediate undergoes proton transfer and elimination of the phosphonium moiety, resulting in product 30 and regeneration of the catalyst. This exceptional demonstration of stereocontrol requires that the catalysts precisely organize both the electrophilic and nucleophilic reactants to

Ionic liquids as transesterification catalysts: applications for the synthesis of linear and cyclic organic carbonates

• Maurizio Selva,
• Alvise Perosa,
• Sandro Guidi and
• Lisa Cattelan

Beilstein J. Org. Chem. 2016, 12, 1911–1924, doi:10.3762/bjoc.12.181

• screening guide. IL-based catalysts for transesterification reactions Synthesis of IL-catalysts: IL-based catalysts for transesterification reactions mostly comprise imidazolium, phosphonium, ammonium, sulfonium and pyridinium salts. The conventional syntheses of such compounds usually start from the

• a fixed bed reactor at 110 °C. The authors indicated the perspective of full industrial application for such a system. Phosphonium salts as catalysts for the selective transesterification of carbonates As mentioned above, the transesterification reaction between organic carbonates and alcohols or

• phenol (Scheme 18), and (iii) all the ILs are produced in very high purity, they are stable for months and usable straight from the reaction vessel. Carbonate, acetate and phenolate phosphonium catalysts were shown to be effective for the mono-transesterification reaction of DMC and DEC with a number of

Total synthesis of leopolic acid A, a natural 2,3-pyrrolidinedione with antimicrobial activity

• Atul A. Dhavan,
• Rahul D. Kaduskar,
• Loana Musso,
• Leonardo Scaglioni,
• Piera Anna Martino and
• Sabrina Dallavalle

Beilstein J. Org. Chem. 2016, 12, 1624–1628, doi:10.3762/bjoc.12.159

• DIBAL-H gave the corresponding primary alcohol, which was converted into bromide 5 by Appel reaction with PPh3 and CBr4. The phosphonium salt obtained from this bromide was subjected to a Wittig reaction with nonanal, to afford compound 6 [12]. Attempts to remove the PMB protecting group (CAN, DDQ, TFA

Synthesis of a deuterated probe for the confocal Raman microscopy imaging of squalenoyl nanomedicines

• Eric Buchy,
• Branko Vukosavljevic,
• Maike Windbergs,
• Dunja Sobot,
• Camille Dejean,
• Simona Mura,
• Patrick Couvreur and
• Didier Desmaële

Beilstein J. Org. Chem. 2016, 12, 1127–1135, doi:10.3762/bjoc.12.109

• from the monoproduct, potassium carbonate treatment gave the expected diepoxide 7. Oxidative cleavage with periodic acid provided the corresponding dialdehyde 5 in 17% overall yield from squalene. The perdeuterated phosphonium salt 9 was obtained by simple condensation of commercially available 2

Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(−)-myrtenol nitrate

• Sean P. Bew,
• Glyn D. Hiatt-Gipson,
• Graham P. Mills and
• Claire E. Reeves

Beilstein J. Org. Chem. 2016, 12, 1081–1095, doi:10.3762/bjoc.12.103

• , the synthesis of either (E)-3-methyl-4-chlorobut-2-en-1-ol ((E)-60) or (Z)-3-methyl-4-chlorobut-2-en-1-ol ((Z)-61, Scheme 8). Reacting triphenylphosphine with 1-((2-bromoethoxy)methyl)-4-methoxybenzene (55) generated non-stabilized phosphonium ylide (2-(4-methoxybenzyloxy)ethyl)triphenylphosphonium