The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• reduction of dibromodifluoromethane was also used for the approach of Burton and Naae (Scheme 4), which is again suitable for electron-rich alkenes [19]. Dibromodifluoromethane reacted with triphenylphosphine to give a phosphonium salt, which then decomposed to difluorocarbene. The yields from this method

Facile synthesis of 7-alkyl-1,2,3,4-tetrahydro-1,8-naphthyridines as arginine mimetics using a Horner–Wadsworth–Emmons-based approach

• Rhys A. Lippa,
• John A. Murphy and
• Tim N. Barrett

Beilstein J. Org. Chem. 2020, 16, 1617–1626, doi:10.3762/bjoc.16.134

• , GlaxoSmithKline disclosed a route to a fluoropyrrolidine 6 using a Wittig reaction between phosphonium salt 4 and aldehyde 5 [2]. The synthesis of phosphonium salt 4 (itself requiring 6 steps including partial saturation of a 1,8-naphthyridine moiety) and the formation of the triphenylphosphine oxide byproduct in

Azidophosphonium salt-directed chemoselective synthesis of (E)/(Z)-cinnamyl-1H-triazoles and regiospecific access to bromomethylcoumarins from Morita–Baylis–Hillman adducts

• Soundararajan Karthikeyan,
• Radha Krishnan Shobana,
• Kamarajapurathu Raju Subimol,
• J. Helen Ratna Monica and
• Ayyanoth Karthik Krishna Kumar

Beilstein J. Org. Chem. 2020, 16, 1579–1587, doi:10.3762/bjoc.16.130

• powerful synthetic tools. Keywords: halomethylcoumarin; Morita–Baylis–Hillman adducts; organocatalyst; phosphonium salt; triazolation; Introduction The presence of versatile functional groups in close proximity classifies Morita–Baylis–Hillman adducts as privileged key scaffolds for synthetic organic

• developing a one-pot synthetic strategy will be worthwhile for pharmacologically important triazoles, such as isavuconazole, tazobactam, and ravuconazole [35]. Results and Discussion Initially, phosphonium salts were barely utilised or exploited in synthetic transformations. Later, in 2014, several organic

• transformations employed quaternary phosphonium salts as favourable catalysts [36]. Their synthetic utility was not only confined to catalysis, but they were also used as intermediates for the synthesis of 1H-indazoles [37], as promoters for stereoselective rearrangements [38], and as temporary protectors of O,P

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• ). Phosphonium ylides, Ph3P+-C−=C=NR (391) reacted with isothiocyanate in a [2 + 2] cycloaddition to form the four-membered ring phosphonium ylides 392, which further reacted with aromatic aldehydes to afford the corresponding arylidene-2,4-diiminothietanes 393 [103] (Scheme 82). Thietan-2-ylideneacetates 397

Synthesis of new asparagine-based glycopeptides for future scanning tunneling microscopy investigations

• Laura Sršan and
• Thomas Ziegler

Beilstein J. Org. Chem. 2020, 16, 888–894, doi:10.3762/bjoc.16.80

• coupling reagents, such as benzotriazol-1-yloxytris(dimethylamino)phosphonium hexafluorophosphate (BOP) or diisopropyl carbodiimide (DIC) and additives, such as 1-hydroxybenzotriazole (HOBt) or triethylphosphine. [29][30][31] However, in our hands, none of the described methods reached the high yields that

Copper-catalyzed O-alkenylation of phosphonates

• Nuria Vázquez-Galiñanes,
• Mariña Andón-Rodríguez,
• Patricia Gómez-Roibás and
• Martín Fañanás-Mastral

Beilstein J. Org. Chem. 2020, 16, 611–615, doi:10.3762/bjoc.16.56

• copper catalyst on an alkenyl(aryl)iodonium salt [33][34] would generate an alkenyl–copper(III) species which might undergo nucleophilic attack of the Lewis-basic oxygen of a dialkyl phosphonate. The resulting phosphonium-like intermediate would evolve by Arbuzov-type substitution of one of the alkyl

Photocontrolled DNA minor groove interactions of imidazole/pyrrole polyamides

• Sabrina Müller,
• Jannik Paulus,
• Jochen Mattay,
• Heiko Ihmels,
• Veronica I. Dodero and
• Norbert Sewald

Beilstein J. Org. Chem. 2020, 16, 60–70, doi:10.3762/bjoc.16.8

• excess of HBTU and could not be completely prevented [44][45]. Since this side reaction did not occur with phosphonium salts, P1 and P3 were successfully obtained by using PyBOP as an activating reagent [45][46]. After final Fmoc cleavage, the polyamides were released from the resin with a solution of

1,5-Phosphonium betaines from N-triflylpropiolamides, triphenylphosphane, and active methylene compounds

• Vito A. Fiore,
• Chiara Freisler and
• Gerhard Maas

Beilstein J. Org. Chem. 2019, 15, 2603–2611, doi:10.3762/bjoc.15.253

• compounds CH2XY in a 1:1:1 molar ratio to furnish 1-phosphonium-5-oxabetaines, Ph3P+–C(R)=CH–C(O–)=CXY. These betaines are formed preferentially, but not exclusively, as E-diastereoisomers with respect to the vinylic double bond. In some cases, separation of the two diastereoisomers was achieved by

• -Michael reaction; propiolamides; Introduction Beside the well-known phosphonium ylides (Wittig ylides, methylenephosphoranes), various other types of zwitterions containing a tetravalent phosphonium moiety (phosphonium betaines) exist. They are often considered as reaction intermediates, but reports on

• -catalyzed reactions of acetylenic ketones and esters with pinacolborane have been discussed [7][8]. The Michael addition of PPh3 at acetylenic carbonyl compounds generates phosphonium/vinyl anion intermediates which have been trapped with CH-, NH-, OH- and SH-acids [5]. In this manner, the 1:1:1 reaction of

A new approach to silicon rhodamines by Suzuki–Miyaura coupling – scope and limitations

• Thines Kanagasundaram,
• Antje Timmermann,
• Carsten S. Kramer and
• Klaus Kopka

Beilstein J. Org. Chem. 2019, 15, 2569–2576, doi:10.3762/bjoc.15.250

• explored the substrate scope of the Suzuki–Miyaura coupling by screening commercially available boronic acids (Scheme 4, Table 2). Hereby, PdCl2(dppf) was also tested in order to suppress the formation of the inseparable phosphonium cation species. At first, we investigated the use of 3-boronobenzoic acid

Synthesis of a dihalogenated pyridinyl silicon rhodamine for mitochondrial imaging by a halogen dance rearrangement

• Jessica Matthias,
• Thines Kanagasundaram,
• Klaus Kopka and
• Carsten S. Kramer

Beilstein J. Org. Chem. 2019, 15, 2333–2343, doi:10.3762/bjoc.15.226

• . Lipophilic cations such as the phosphonium cation or rhodamines are known to accumulate selectively within the mitochondria, driven by the mitochondrial plasma membrane potential [39][40]. Thereby, the high lipophilicity facilitates the diffusion through the lipid bilayers of the cell and mitochondrial

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