New triazinephosphonate dopants for Nafion proton exchange membranes (PEM)

• Fátima C. Teixeira,
• António P. S. Teixeira and
• C. M. Rangel

Beilstein J. Org. Chem. 2024, 20, 1623–1634, doi:10.3762/bjoc.20.145

• commercially available and were prepared from 4-hydroxyphenyl- or 4-aminophenyl-based derivatives. The first nucleophile to be synthesized was diethyl (4-hydroxyphenyl)phosphonate (2) [51], starting from 4-bromophenol (3) and triethyl phosphite. When this reaction was carried out in the presence of nickel(II

• ] was also prepared, using the same reaction conditions, by the reaction between 1-bromo-4-nitrobenzene (5) and diethyl phosphonate, in the presence of Pd(PPh3)4 as catalyst and triethylamine, since the use of triethyl phosphite in the presence on nickel(II) bromide do not allow the formation of the

• nucleophilic substitution using hydrobromic acid, as a 33% solution in acetic acid, to afford the corresponding bromide derivative 9 [54] (Scheme 2). Subsequently 1-(benzyloxy)-4-(bromomethyl)benzene (9) underwent Michaelis–Arbuzov reaction with triethyl phosphite to afford diethyl [4-(benzyloxy)phenyl

Identification and determination of the absolute configuration of amorph-4-en-10β-ol, a cadinol-type sesquiterpene from the scent glands of the African reed frog Hyperolius cinnamomeoventris

• Angelique Ladwig,
• Markus Kroll and
• Stefan Schulz

Beilstein J. Org. Chem. 2023, 19, 167–175, doi:10.3762/bjoc.19.16

• cleanly obtained in 75% yield from triethyl phosphite and 3-chloro-2-methylpropene by addition of NaI [14]. Subsequent reduction of the ester with LiAlH4 and oxidation with IBX gave aldehyde 7 in 95% yield. Grignard addition of vinylmagnesium bromide afforded the alcohol 8, which comprised the desired

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• ][72]. A recent achievement of the enantioselective hydroxylation of α‑aryl-δ-lactams by O2 is shown in Scheme 5 [73] as an example of such organocatalyzed reaction type. Triethyl phosphite is added to reduce a hydroperoxide, which is initially formed by the enolate oxidation with O2. In summary

An alternative C–P cross-coupling route for the synthesis of novel V-shaped aryldiphosphonic acids

• Stephen J. I. Shearan,
• Enrico Andreoli and
• Marco Taddei

Beilstein J. Org. Chem. 2022, 18, 1518–1523, doi:10.3762/bjoc.18.160

• which phosphite is chosen. In this case, triisopropyl phosphite has been chosen over commonly employed triethyl phosphite, since the latter results in a more reactive alkyl halide (i.e., ethyl bromide), which would react with triethyl phosphite to produce diethyl ethylphosphonate, thus consuming the

• triethyl phosphite in a competing reaction and introducing undesired side products that would make the workup procedure more laborious. Furthermore, the boiling point of triisopropyl phosphite is 181 °C, versus 156 °C for triethyl phosphite, which allows to run the reaction at higher temperature and reduce

Direct C–H amination reactions of arenes with N-hydroxyphthalimides catalyzed by cuprous bromide

• Dongming Zhang,
• Bin Lv,
• Pan Gao,
• Xiaodong Jia and
• Yu Yuan

Beilstein J. Org. Chem. 2022, 18, 647–652, doi:10.3762/bjoc.18.65

• the amidyl radical precursor under air is reported. A possible mechanism is proposed that proceeds via a radical reaction in the presence of CuBr and triethyl phosphite. Keywords: amination; copper; N-hydroxyphthalimides; radical reactions; triethyl phosphite; Introduction Practical methods for

• (40 mol %) in the presence of P(OEt)3 (6 equiv, triethyl phosphite) under air at 100 °C (Table 1). The yield of the corresponding amide 3a was 78% (Table 1, entry 1). The reaction was completely inhibited in the absence of the copper catalyst or P(OEt)3, and no product was detected (Table 1, entries 2

• and 3). Different copper salts were tested and the reactions proved to be less efficient (Table 1, entries 4 and 5). Except for triethyl phosphite, the reaction could not be carried out with other phosphorus species (Table 1, entries 6–8). The optimum result was obtained when benzene was employed as

Silica gel and microwave-promoted synthesis of dihydropyrrolizines and tetrahydroindolizines from enaminones

• Robin Klintworth,
• Garreth L. Morgans,
• Stefania M. Scalzullo,
• Charles B. de Koning,
• Willem A. L. van Otterlo and
• Joseph P. Michael

Beilstein J. Org. Chem. 2021, 17, 2543–2552, doi:10.3762/bjoc.17.170

• bromide in acetonitrile at ambient temperature to produce the putative S-alkylated salt was complete within 18 hours, after which treatment with triethyl phosphite and triethylamine rapidly completed the sulfide contraction, giving (E)-enaminone 15a in 92% yield after chromatographic purification. The

• [57][58][59][60][61][62][63][64][65]. Results are summarized in Table 2. Triphenylphosphine and triethyl phosphite could be used interchangeably in the sulfur extrusion step. However, in most cases the co-elution of enaminones 15 with phosphorus-derived byproducts during chromatographic purification

• and 4-nitro congeners in acetonitrile, followed by sulfide contraction of the resulting thioiminium ether salts with triethylamine and triethyl phosphite, afforded the (E)-enaminones 25a–c in yields of 86–89%. The E-geometry of 25a was again confirmed by NOESY NMR spectroscopy, which showed an

Progress in the total synthesis of inthomycins

• Bidyut Kumar Senapati

Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7

• bromine in acetic acid, and then triethyl phosphite. Next, compound 28 was treated with sodium hydride followed by aldehyde 29 [37] to give (E,E)-dienyl stannane 30 in 50% yield. The key Stille coupling between 30 and vinyl iodide 31, prepared by Takai reaction [38] of phenylacetaldehyde, in presence of

Synthesis and characterization of S,N-heterotetracenes

• Astrid Vogt,
• Florian Henne,
• Christoph Wetzel,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2020, 16, 2636–2644, doi:10.3762/bjoc.16.214

• derivatives by Cadogan reaction of nitro-substituted precursors. Another possibility for the preparation of fused pyrrole rings is established by the Cadogan reaction [40]. Well-known examples are the reductive cyclization of 2-nitro-1,1’-biphenyls with triethyl phosphite or phosphanes as reducing agent to

• 3-nitro-2,2’-bithiophene with triethyl phosphite under microwave irradiation and surprisingly obtained targeted heterotriacene H-DTP (vide supra) with only 11% yield [45]. This result prompted us to have a closer look on the applicability of the Cadogan reaction/cyclization in order to provide S,N

• a Pd-catalyzed Stille-type cross-coupling with 2-bromo-3-nitrothiophene (15) to precursor 2-(3-nitrothien-2-yl)thieno[3,2-b]thiophene (16) in 64% yield. Cadogan cyclization of nitro derivative 16 with triethyl phosphite at reflux gave 4H-thieno[3,2-b]thieno[2’, 3’:4,5]thieno[2,3-d]pyrrole (H-SN4, 13

Synthesis and properties of tetrathiafulvalenes bearing 6-aryl-1,4-dithiafulvenes

• Aya Yoshimura,
• Hitoshi Kimura,
• Kohei Kagawa,
• Mayuka Yoshioka,
• Toshiki Itou,
• Dhananjayan Vasu,
• Takashi Shirahata,
• Hideki Yorimitsu and
• Yohji Misaki

Beilstein J. Org. Chem. 2020, 16, 974–981, doi:10.3762/bjoc.16.86

• ; one was the palladium-catalyzed C–H arylation of TTF with bromide 12 (Scheme 2a) and the other was the Vilsmeier–Haack reaction of 1a, followed by triethyl phosphite-mediated cross coupling with 11 (Scheme 2b). Theoretical calculations The DFT calculations of compounds 1a, 3a, and 4 have been carried

Preactivation-based chemoselective glycosylations: A powerful strategy for oligosaccharide assembly

• Weizhun Yang,
• Bo Yang,
• Sherif Ramadan and
• Xuefei Huang

Beilstein J. Org. Chem. 2017, 13, 2094–2114, doi:10.3762/bjoc.13.207

• thioglycosyl donor. The sulfide triflate 73 could activate the thioglycoside product, which provides a possible explanation for the modest yield. To avoid the side reaction caused by 73, triethyl phosphite was added as a scavenger to quench 73, which enhanced the glycosylation yield to 78%. The need for

• triethyl phosphite to prevent the undesired acceptor/product activation precludes the possibility of carrying out multiple glycosylation reactions in one pot using BSP/Tf2O. Other promoter systems such as NIS/TMSOTf, Ph2SO/Tf2O and BSM/Tf2O have similar complications due to the formation of thiophilic or

• ; then 96, and triethyl phosphite; (b) p-TolSCl/AgOTf, −60 °C; then 99. One-pot synthesis of Globo-H hexasaccharide 105 using building blocks 101, 102, 103 and 104. Synthesis of (a) oligosaccharides 109–113 towards (b) 30-mer galactan 115. Reagents and conditions: (a) TTBP, 4 Å MS, CH2Cl2, p-TolSCl

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

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

• , followed by thermal Arbuzov rearrangement of the intermediate allyl phosphites (Scheme 1, reaction 1). Recently, an efficient protocol for the conversion of common allyl and benzyl alcohols into the corresponding phosphonates through their treatment with triethyl phosphite and ZnI2, was described [16

• ]. Similarly, Das and co-workers [17] have directly converted acyclic Morita–Baylis–Hillman (MBH) alcohols into the corresponding allylphosphonates upon their treatment with trialkyl phosphite in the presence of FeCl3 (Scheme 1, reaction 2). On the other hand, treatment of MBH acetates with triethyl phosphite

• conversion of these γ-ketoallylphosphonates into related γ-aminoallylphosphonates. Results and Discussion In our first attempt, a mixture of cyclic MBH alcohol 1a and triethyl phosphite was reacted in toluene without any additive. After stirring the reaction mixture at 110 °C for 72 h, the starting materials

Microwave-assisted synthesis of (aminomethylene)bisphosphine oxides and (aminomethylene)bisphosphonates by a three-component condensation

• Erika Bálint,
• Ádám Tajti,
• Anna Dzielak,
• Gerhard Hägele and
• György Keglevich

Beilstein J. Org. Chem. 2016, 12, 1493–1502, doi:10.3762/bjoc.12.146

• (Scheme 2a) [33], by the condensation of formamides and diethyl phosphite using 2,6-di-tert-butyl-4-methylpyridine (DTBMP) as the base, and trifluoromethanesulfonic anhydride (Tf2O) as the catalyst (Scheme 2b) [34], or by the reaction of isonitriles with triethyl phosphite (Scheme 2c) [35][36

• ]. (Aminomethylene)bisphosphonates can also be obtained starting from amides, triethyl phosphite and phosphorus oxychloride (Scheme 3a) [37], or in the reaction of amines with diazophosphonate in the presence of a rhodium catalyst (Scheme 3b) [38]. (Aminomethylene)bisphosphine oxides are analogous to (aminomethylene

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

• Mohammad Haji

Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121

• -Boc-3-piperidinone (37), (S)-configured amines 39 and triethyl phosphite (38), in the presence of 2 equiv of AcOH and 0.8 equiv of MgSO4 at 50 °C afforded a 60:40 diastereomeric mixture of α-aminophosphonates (R,S)-40 and (S,S)-41 in 75% combined yield. The cleavage of the N-Boc group followed by

• and superoxide radicals [38]. 2.2.2 2-Phosphono-6-oxazolopiperidines: An asymmetric Kabachnik–Fields reaction between (R)-(−)-phenylglycinol (50), glutaraldehyde (51) and triethyl phosphite has been reported by Royer et al. The reaction furnished a diastereomeric mixture of 2-phosphono-6

• arylaldehydes 64 or 68 afforded the corresponding 3-arylmethyleneisoindolin-1-ones 65 and 69, respectively (Scheme 16) [42][43]. Recently, an efficient method was developed for the synthesis of ethyl (2-alkyl- and 2-aryl-3-oxoisoindolin-1-yl)phosphonates 71 from 2-formylbenzoic acid (55), triethyl phosphite and

Synthesis of racemic and chiral BEDT-TTF derivatives possessing hydroxy groups and their achiral and chiral charge transfer complexes

• Sara J. Krivickas,
• Chiho Hashimoto,
• Junya Yoshida,
• Akira Ueda,
• Kazuyuki Takahashi,
• John D. Wallis and
• Hatsumi Mori

Beilstein J. Org. Chem. 2015, 11, 1561–1569, doi:10.3762/bjoc.11.172

• and acetic acid in chloroform. Oxo compound 11 was then cross-coupled with 1.2 equivalents of thione 12 in triethyl phosphite to afford the racemic protected donor 13 in reasonable yield (37%). Basic hydrolysis of the acetyl protecting group afforded the racemic donor 1 in an 81% yield. The syntheses

• equiv) and the oxo-compound 11 (480 mg, 1.63 mmol, 1 equiv) in triethyl phosphite (10 mL) was stirred overnight at 90 °C. After cooling, hexane was added and the precipitate collected by vacuum filtration and purified by column chromatography (silica gel, 4:1 hexane/ethyl acetate) to afford the cross

• mmol, 2 equiv) and oxo compound (S,S)-16 (50 mg, 0.14 mmol, 1 equiv) in triethyl phosphite (2 mL) was stirred at 90 °C for 5 hours. After cooling hexane was added, the precipitate collected and purified by column chromatography (silica gel, hexane/ethyl actetate) to afford the enantiopure cross coupled

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

• -picoline [20]. In 1989, Schrader and Steglich described an example of synthesis of diethyl 1-(N-acylamino)-1-[ethoxy(methylphosphinyl)]methylphosphonate using a Michaelis–Arbuzov-like condensation of the corresponding ethyl [1-(N-acylamino)-1-bromomethyl]methylphosphinate with triethyl phosphite in 79

• acid esters was mentioned in the literature only once, in relation to α-methoxylation of diethyl N-benzoylaminomethylphosphonate [42]. Attempts to carry out a Michaelis–Arbuzov-like reaction of the obtained diethyl 1-(N-acetylamino)-1-methoxyalkylphosphonates with triethyl phosphite failed due to still

Thiazole-induced rigidification in substituted dithieno-tetrathiafulvalene: the effect of planarisation on charge transport properties

• Rupert G. D. Taylor,
• Joseph Cameron,
• Iain A. Wright,
• Neil Thomson,
• Olena Avramchenko,
• Alexander L. Kanibolotsky,
• Anto R. Inigo,
• Tell Tuttle and
• Peter J. Skabara

Beilstein J. Org. Chem. 2015, 11, 1148–1154, doi:10.3762/bjoc.11.129

• constructing a half-unit functionalised with a 1,3-dithiol-2-one, that can undergo a triethyl phosphite-mediated homocoupling to synthesise the central dithienoTTF in the final step. Herein, we present an alternative divergent route to dithienoTTFs, by utilising 4,6,4’,6’-tetrabromo-[2,2’]bis(thieno[3,4-d][1,3

• ]dithiolylidene) [15] as a core and appending heterocyclic arms through microwave assisted Stille couplings. It is worth noting that the tetrabromo-dithienoTTF core is still prepared via a triethyl phosphite-mediated homocoupling, but in this divergent route valuable heterocyclic groups can be introduced at the

• the synthesis of a half-unit and a final triethyl phosphite mediated homo-coupling. The resultant compounds, 1 and 2, were fully characterised and their optical and electrochemical properties elucidated via UV–vis spectroscopy and cyclic voltammetry, and explained in conjunction with DFT level

Advances in the synthesis of functionalised pyrrolotetrathiafulvalenes

• Luke J. O’Driscoll,
• Sissel S. Andersen,
• Marta V. Solano,
• Dan Bendixen,
• Morten Jensen,
• Troels Duedal,
• Jess Lycoops,
• Cornelia van der Pol,
• Rebecca E. Sørensen,
• Karina R. Larsen,
• Kenneth Myntman,
• Christian Henriksen,
• Stinne W. Hansen and
• Jan O. Jeppesen

Beilstein J. Org. Chem. 2015, 11, 1112–1122, doi:10.3762/bjoc.11.125

• derivatives can be prepared from 6 and 7 by means of coupling reactions in triethyl phosphite (Scheme 3). The known homocoupling reaction of 6 affords the bis-tosylated BPTTF 5a in high yield with minimal purification [25]. We have obtained a comparable yield (76% vs 84%) working at twice the previously

A hybrid electron donor comprising cyclopentadithiophene and dithiafulvenyl for dye-sensitized solar cells

• Gleb Sorohhov,
• Chenyi Yi,
• Michael Grätzel,
• Silvio Decurtins and
• Shi-Xia Liu

Beilstein J. Org. Chem. 2015, 11, 1052–1059, doi:10.3762/bjoc.11.118

• (0.160 g, 0.5 mmol) in toluene (50 mL) was added dropwise into a hot solution of 3 (0.212, 0.5 mmol) and triethyl phosphite (10 mL) in toluene (50 mL) under nitrogen protection. The resulting mixture was stirred at reflux overnight. After removing the solvent under reduced pressure, the residue was

• (hexylthio)-1,3-dithiole-2-thione (0.090 g, 0.2 mmol) in toluene (50 mL) was added dropwise into a hot solution of 5 (0.101 g, 0.2 mmol) and triethyl phosphite (5 mL) in toluene (100 mL) under nitrogen protection. The resulting mixture was stirred at reflux overnight. After removing the solvent under reduced

Synthesis and characterization of the cyanobenzene-ethylenedithio-TTF donor

• Sandrina Oliveira,
• Dulce Belo,
• Isabel C. Santos,
• Sandra Rabaça and
• Manuel Almeida

Beilstein J. Org. Chem. 2015, 11, 951–956, doi:10.3762/bjoc.11.106

• -tetrathiafulvalene (CNB-EDT-TTF), was obtained in high yield, by a cross-coupling reaction with triethyl phosphite between 2-thioxobenzo[d][1,3]dithiole-5-carbonitrile and 5,6-dihydro-[1,3]dithiolo[4,5-b][1,4]dithiin-2-one. This new donor was characterized namely by single crystal X-ray diffraction, cyclic

• pure triethyl phosphite during 4 hours at 130 °C leading to the formation of 3 in relatively high yield (63%) (Scheme 1). This coupling reaction also gives rise to smaller amounts of BEDT-TTF (14% yield) and dicyanodibenzene tetrathiafulvalene (dcdb-TTF) [13] as byproducts resulting from homocoupling

• anisotropic thermal parameters whereas H-atoms were placed in idealised positions and allowed to refine riding on the parent C atom. Molecular graphics were prepared using MERCURY 1.4.2 [29]. General procedure for the synthesis of 3 In freshly destilled triethyl phosphite (10 mL), 2-thioxobenzo[d][1,3

Bis(vinylenedithio)tetrathiafulvalene analogues of BEDT-TTF

• Erdal Ertas,
• İlknur Demirtas and
• Turan Ozturk

Beilstein J. Org. Chem. 2015, 11, 403–415, doi:10.3762/bjoc.11.46

• % yields. The fully unsaturated tetraphenyl analogue 52 of ET was obtained in 90% yield by a coupling reaction of 51, which was obtained by converting the thione group of 48 to its corresponding oxo form in 85% yield, in hot triethyl phosphite, yielding 52 in 90% yield (Scheme 7). A charge transfer salt 54

• coupling of 28 with 51 smoothly gave the corresponding ET analogue 56, its reaction with 57 did not produce any result (Scheme 9) [57]. This could be due to the reaction of the benzylphenyldithiole moiety with triethyl phosphite. Analogues of ET, having dithiin and thiophene rings along with hydroxy groups

• lead to side products during the coupling reaction, performed using triethyl phosphite, and the reaction for conversion of the thione group to a keto group with mercury acetate and acetic acid, they were protected by reaction with methoxyethoxymethylchloride (CH3OCH2CH2OCH2Cl, MEMCl) to obtain 62. The

A simple and efficient method for the preparation of 5-hydroxy-3-acyltetramic acids

• Johanna Trenner and
• Evgeny V. Prusov

Beilstein J. Org. Chem. 2015, 11, 323–327, doi:10.3762/bjoc.11.37

• turned to the alternative oxidation of enolates with molecular oxygen in the presence of triethyl phosphite as originally described by Hartwig [12][13][14][15]. Application of these conditions resulted in a clean conversion to the 5-hydroxy-3-acyltetramic acid but again, the isolated yield of the product

Stability of SG1 nitroxide towards unprotected sugar and lithium salts: a preamble to cellulose modification by nitroxide-mediated graft polymerization

• Guillaume Moreira,
• Laurence Charles,
• Mohamed Major,
• Florence Vacandio,
• Yohann Guillaneuf,
• Catherine Lefay and
• Didier Gigmes

Beilstein J. Org. Chem. 2013, 9, 1589–1600, doi:10.3762/bjoc.9.181

• Erba), ethyl acetate (EtOAc, Carlo Erba), triethyl phosphite (P(O)(OEt)3, Aldrich, 99+% ), and tert-butylbenzene (t-BuPh, Aldrich, 99%) were used as received. The 2-methyl-2-(N-tert-butyl-N-(1-diethoxyphosphoryl-2,2-dimethylpropyl)aminoxy)-propionic acid alkoxyamine (BlocBuilder MA, BB) was kindly

Methylidynetrisphosphonates: Promising C₁ building block for the design of phosphate mimetics

• Vadim D. Romanenko and
• Valery P. Kukhar

Beilstein J. Org. Chem. 2013, 9, 991–1001, doi:10.3762/bjoc.9.114

• from simple trihalomethyl derivatives [10][11][12]. Indeed, chloroform and bromoform do not react with triethyl phosphite even under harsh conditions [11]. In addition, no reaction occurred between benzotrichloride (PhCCl3) and triethyl phosphite at a temperature below 150 °C. The CuCl-catalyzed

• reaction of PhCCl3 and (EtO)3P at 120–140 °C produced 1,2-diphenyl-1,1,2,2-tetrachloroethane [13]. The early work reported that the trisphosphonate PhC(PO3Et2)3 was formed from triethyl phosphite and dibenzoyl peroxide when reagents were boiled under reflux in chloroform, but proof of the trisphosphonate

• structure was provided [16][17]. The first authentic synthesis of 1,1,1-trisphosphonate derivatives 1a,b was described by Kukhar, Pasternak and Kirsanov by allowing the addition of triethyl phosphite to dichloromethylene dialkylammonium chloride to proceed in dichloromethane at −40 °C (Scheme 1) [18]. Other

An improved synthesis of a fluorophosphonate–polyethylene glycol–biotin probe and its use against competitive substrates

• Hao Xu,
• Hairat Sabit,
• Gordon L. Amidon and
• H. D. Hollis Showalter

Beilstein J. Org. Chem. 2013, 9, 89–96, doi:10.3762/bjoc.9.12

• combined 90% yield. The phosphonate moiety was installed under standard Arbuzov conditions by heating 4b under reflux in neat triethyl phosphite for 1 h to provide novel intermediate 5 in 92% yield following purification by column chromatography. Clean removal of the benzyl protecting group under standard

• -phenyl-2,5,8,11-tetraoxatridecan-13-yl)phosphonate (5): Iodobenzyl polyether 4b (17.44 g, 44.23 mmol) and triethyl phosphite (32 mL, 183.9 mmol) were mixed in an oven-dried round-bottom flask and heated under reflux for 1 h. Excess triethyl phosphite was removed under vacuum and the reaction mixture was