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

One-pot synthesis of enantiomerically pure N-protected allylic amines from N-protected α-amino esters

• Gastón Silveira-Dorta,
• Sergio J. Álvarez-Méndez,
• Víctor S. Martín and
• José M. Padrón

Beilstein J. Org. Chem. 2016, 12, 957–962, doi:10.3762/bjoc.12.94

• ]. However, that preliminary study was limited to the use of phosphonium ylide reagents and commonly t-Boc (iBoc and Ac were used once) as N-protecting group. To the best of our knowledge, no further studies on the reaction conditions have been carried out. Instead, the method was applied to N-Ac aspartic

• -membered ring lactams [20]. Finally, a one-pot reduction-olefination involving an α-amino β-hydroxy ester and a phosphonium salt, both bearing free hydroxy groups, has been used in the synthesis of (−)-α-conhydrine [21]. In this work, our aim was to study in more detail this one-pot strategy. Similarly to

• Discussion The experimental procedure for the tandem reduction–Wittig olefination synthesis of allylic amines reported the use of toluene as solvent for the reduction step and THF as solvent to prepare the phosphonium ylide [17]. Consequently, the Wittig olefination takes place in a 2:1 (toluene/THF) solvent

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

• work-up involved simple filtration and washing with toluene. Use of t-BuOK as a base to deprotonate the phosphonium salt resulted in a dark red phosphorous ylide, to which 1-(triisopropylsilyl)-1H-pyrrole-3-carbaldehyde was added, followed by heating at 80 °C. The desired product 4c was obtained in 40

Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

• Kevin Lafaye,
• Cyril Bosset,
• Lionel Nicolas,
• Amandine Guérinot and
• Janine Cossy

Beilstein J. Org. Chem. 2015, 11, 2223–2241, doi:10.3762/bjoc.11.241

• catalyst (Table 1, entries 2 and 3). Interestingly the sp2 amine DBU did not induce any decomposition of the methylidene intermediate (Table 1, entry 4). In all decomposition cases, the main identified product was the phosphonium CH3PCy3+Cl− that would result from a nucleophile attack of the free PCy3

Ruthenium indenylidene “1^st generation” olefin metathesis catalysts containing triisopropyl phosphite

• Stefano Guidone,
• Fady Nahra,
• Alexandra M. Z. Slawin and
• Catherine S. J. Cazin

Beilstein J. Org. Chem. 2015, 11, 1520–1527, doi:10.3762/bjoc.11.166

• in vacuo. The crude product was recrystallized from dichloromethane/pentane. The solid was collected by filtration and washed with pentane (3 × 3 mL). The product was obtained as a brownish green solid in a mixture with the phosphonium ylide 3 (0.032 g, 35%). 1H NMR of the mixture (400 MHz, CD2Cl2) δ

A new method for the synthesis of α-aminoalkylidenebisphosphonates and their asymmetric phosphonyl-phosphinyl and phosphonyl-phosphinoyl analogues

• Anna Kuźnik,
• Roman Mazurkiewicz,
• Mirosława Grymel,
• Katarzyna Zielińska,
• Jakub Adamek,
• Ewa Chmielewska,
• Marta Bochno and
• Sonia Kubica

Beilstein J. Org. Chem. 2015, 11, 1418–1424, doi:10.3762/bjoc.11.153

• -methoxyalkylphosphonic acid derivatives, their methoxy group was successfully displaced by the triphenylphosphonium group. Thus, heating the homogeneous mixture of diethyl 1-(N-acetylamino)-1-methoxymethylphosphonate (6a) with triphenylphosphonium tetrafluoroborate at 50 °C gave hitherto unknown phosphonium salt 7a as a

• resin-like compound stable at room temperature (Scheme 2). In the case of 1-(N-acetylamino)-1-methoxyethylphosphonate (6b), the analogous reaction with triphenylphosphonium tetrafluoroborate proceeded very quickly, without heating, but the resulting phosphonium salt 7b underwent slow decomposition even

• the corresponding phosphonium salts. Antiresorptive potency of selected α-amino and α-hydroxy derivatives of bisphosphonates [3][7][8]. Electrochemical α-methoxylation of diethyl 1-(N-acetylamino)alkylphosphonates 5 (R = Me). Reaction of diethyl 1-(N-acetylamino)-1-triphenylphosphoniumalkylphosphonate

A small azide-modified thiazole-based reporter molecule for fluorescence and mass spectrometric detection

• Stefanie Wolfram,
• Hendryk Würfel,
• Stefanie H. Habenicht,
• Christine Lembke,
• Phillipp Richter,
• Eckhard Birckner,
• Rainer Beckert and
• Georg Pohnert

Beilstein J. Org. Chem. 2014, 10, 2470–2479, doi:10.3762/bjoc.10.258

• by introduction of charged species like ammonium or phosphonium for ionization in the positive mode [18][19][20]. Bromine [19][21][22] or chlorine [23] containing tags were also introduced as they generate a unique isotopic pattern and therefore enhance recognition and identification of labeled small

Molecular recognition of AT-DNA sequences by the induced CD pattern of dibenzotetraaza[14]annulene (DBTAA)–adenine derivatives

• Marijana Radić Stojković,
• Marko Škugor,
• Łukasz Dudek,
• Jarosław Grolik,
• Julita Eilmes and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2175–2185, doi:10.3762/bjoc.10.225

• phosphonium substituents as intriguing AT binders, which showed very rare kinetic differentiation between alternating- and homo-AT-DNA sequences [6]. Moreover, these dyes efficiently entered cells and were shown to be non-toxic, mitochondria-specific fluorescent markers [7]. Previous studies also revealed the

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

• summarized splendidly in several reviews, we do not cover these transformations, except for selected examples related to other reactions. Review 1 Chiral phosphine catalysts Nucleophilic phosphine catalysis often involves the formation of Lewis adducts, namely phosphonium (di)enolate zwitterions, as reaction

• substrates favored the formation of the products. Based on control experiments and aforementioned results, Barbas and co-workers proposed a plausible mechanism and suggested that the high stereoselectivity resulted from steric interactions between the bulky substituent of the phosphonium ylide from the MBH

• phosphine, it is quite interesting and deserves mention. In the presence of cesium carbonate, chiral BIPHEP-derived phosphonium ylides reacted with various α,β-unsaturated aryl/alkylketones in THF at room temperature to afford corresponding cyclohexadienes in good yields and with up to 90% ee. It was

Organophosphorus chemistry

• Paul R. Hanson

Beilstein J. Org. Chem. 2014, 10, 2087–2088, doi:10.3762/bjoc.10.217

• their use as recyclable heterogeneous reagents, the Atherton–Todd reaction, cyclic phosphonium ionic liquids with distinct properties, photo-removable phosphate protecting groups, new methods of C–H functionalization using phosphoryl-related directing groups, the exciting chemistry of substituted

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

Efficient CO₂ capture by tertiary amine-functionalized ionic liquids through Li⁺-stabilized zwitterionic adduct formation

• Zhen-Zhen Yang and
• Liang-Nian He

Beilstein J. Org. Chem. 2014, 10, 1959–1966, doi:10.3762/bjoc.10.204

• ], novel electrolytes for energy applications [20][21], and efficient absorbents for gas separation [2][22][23][24]. In particular, amino-functionalized IL [APBIm][BF4] (1-aminopropyl-3-butylimidazolium tetrafluoroborate) and ILs being composed of amino acid (AA) anions and phosphonium or ammonium cations

• ). Notably, equimolar CO2 absorption was obtained using task-specific ionic liquids (TSILs) with the phosphonium cation containing long alkyl chains and anions derived from AAs (prolinate and methioninate) [36], or AA salts with bulky N-substituents in polyethylene glycol (PEG) solution [37]. However

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

• Abstract (1H-Benzo[d][1,2,3]triazol-1-yloxy)tris(dimethylamino)phosphonium hexafluorophosphate (BOP), 1H-benzo[d][1,2,3]triazol-1-yl 4-methylbenzenesulfonate (Bt-OTs), and 3H-[1,2,3]triazolo[4,5-b]pyridine-3-yl 4-methylbenzenesulfonate (At-OTs) are classically utilized in peptide synthesis for amide-bond

• , and other chemical experiments, phosphonium and tosylate derivatives of alcohols seem to be intermediates. These then react with BtO− and AtO− produced in situ. In order to demonstrate broader utility, this novel reaction has been used to prepare a series of acyclic nucleoside-like compounds. Because

• ][1,2,3]triazole, via in situ formation of pyrrolidine enamines and Pd catalysis. Keywords: alkoxy; azabenzotriazole; benzotriazole; peptide-coupling; phosphonium; Introduction Benzotriazole derivatives are of importance in diverse contexts. As examples, in medicinal chemistry substituted benzotriazoles

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

• rasta resin-supported triphenylphosphine oxide 16, and have applied it as a phosphonium halide salt precursor in a wide range of halogenation reactions from which it is readily recovered and reused. The reusability of this polymer was demonstrated by the fact that all of the reactions reported herein

Automated solid-phase peptide synthesis to obtain therapeutic peptides

• Veronika Mäde,
• Sylvia Els-Heindl and
• Annette G. Beck-Sickinger

Beilstein J. Org. Chem. 2014, 10, 1197–1212, doi:10.3762/bjoc.10.118

• )methylene]-N-methylmethanaminium tetrafluoroborate N-oxide) [57]), and phosphonium salts (PyBOP (benzotriazol-1-yloxytri(pyrrolidino)phosphonium hexafluorophosphate) [58]) (Figure 3). In 2009, Oxyma (ethyl 2-cyano-2-(hydroxyimino)acetate) [59][60] was introduced as a novel additive for DIC-mediated peptide

Atherton–Todd reaction: mechanism, scope and applications

• Stéphanie S. Le Corre,
• Mathieu Berchel,
• Hélène Couthon-Gourvès,
• Jean-Pierre Haelters and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2014, 10, 1166–1196, doi:10.3762/bjoc.10.117