Sodium Trifluoroethoxide Research Articles

Chemical Diversification of Sialic Acid Glycosides by Stereospecific, Chemoselective Deamination

Late bloomer: Nitrosation of peracetylated sialic acid glycosides followed by treatment with sodium trifluoroethoxide and then a suitable nucleophile enables the late-stage modification of these glycosides with stereospecific replacement of the acetamido group. This method should enable access to many glycoside derivatives with a minimum of synthetic effort.

Substituent Exchange Reactions with High Polymeric Organophosphazenes

Side group exchange reactions have been studied for linear high polymeric organophosphazenes, [N═P(OR2)]n (n ∼ 15 000). Specifically, the exchange behavior of polymers was examined where OR = OCH2CF3, OCH2CF2CF2CF2CF2H, OCH2Cl3, OC6H4CHO-p, OC6H4CN-p, and OC6H4NO2-p with sodium trifluoroethoxide. No aryloxy group replacement by trifluoroethoxy was detected, probably due to the well-protected reactive sites of the polyphosphazenes shielded by aryloxy side groups. For the exchange behavior of [N═P(OCH2CF3)2]n and [N═P(OCH2CF2CF2CF2CF2H)2]n with NaOCH2CF2CF2CF2CF2H and NaOCH2CF3, partial substituent exchange was achieved for both reactions. Furthermore, under conditions with excess nucleophile these side group exchange reactions are followed by reactions that introduce sodium–oxo groups attached to phosphorus in place of organic substituents, and this is a mechanism for subsequent hydrolysis and molecular weight decline in the presence of water. Thus, the relative instability of high polymeric [N═P(OCH2CF3)2...

Substituent Exchange Reactions of Linear Oligomeric Aryloxyphosphazenes with Sodium 2,2,2-Trifluoroethoxide

Side-group-exchange reactions have been studied for short-chain linear oligomeric phosphazenes, (RO)(4)P[N═P(OR(2))](n)OR (n = 6, 10, 20, and 40) as models for the corresponding linear high polymers (n ~ 15000). Specifically, the exchange behavior of oligomers where OR = OCH(2)CF(3), OC(6)H(5), OC(6)H(4)CHO-p, OC(6)H(4)CN-p, and OC(6)H(4)NO(2)-p with sodium trifluoroethoxide was examined. The ease of aryloxy group replacement by trifluoroethoxy increased with the electron-withdrawing character in the order OR = OC(6)H(5) ≪ OC(6)H(4)CHO-p < OC(6)H(4)CN-p < OC(6)H(4)NO(2)-p, but the reaction was efficient only if the phosphazene contained no more than 20 repeating units. However, attempts to force slower reactions by the use of excess sodium trifluoroethoxide induced secondary reactions at the trifluoroethoxy units already introduced to produce CF(3)CH(2)OCH(2)CF(3) and generate -O(-)Na(+) units in their place. The longest chain model underwent side-group-exchange reactions preferentially at the end units. These results are significant for the synthesis of phosphazene high polymers with fluoroalkoxy and aryloxy side groups.

Synthesis and Micellar Behavior of Novel Amphiphilic Poly[bis(trifluoroethoxy)phosphazene]-co-poly[(dimethylamino)ethyl methacrylate] Block Copolymers

A number of amphiphilic diblock copolymers based on poly[bis(trifluoroethoxy)phosphazene] (TFE) as the hydrophobic block and poly[(dimethylamino)ethyl methacrylate] (PDMAEMA) as the hydrophilic block were developed. The TFE block was synthesized first by the controlled living cationic polymerization of a phosphoranimine, followed by replacement of all the chlorine atoms using sodium trifluoroethoxide. To allow for the growth of the PDMAEMA block, 3-azidopropyl-2-bromo-2-methylpropanoate, an atom transfer radical polymerization (ATRP) initiator, was grafted onto the end-cap of the TFE block via the “click” reaction followed by the ATRP of 2-(dimethylamino)ethyl methacrylate (DMAEMA). Once synthesized, micelles were formed by a standard method, and their characteristics were examined using fluorescence techniques, dynamic light scattering, and transmission electron microscopy. The critical micelle concentrations of the diblock copolymers as determined by fluorescence techniques using pyrene as a hydrophobic probe were between 3.47 and 9.55 mg/L, with the partition equilibrium constant of pyrene in these micelles ranging from 0.12 × 105 to 1.52 × 105. The diameters measured by dynamic light scattering were 100–142 nm at 25 °C with a narrow distribution, which were also confirmed by transmission electron microscopy.

Dispersion of Single-Walled Carbon Nanotubes in Water with Polyphosphazene Polyelectrolyte

A polyphosphazene polyelectrolyte was prepared as a dispersing agent of SWNTs in water. Poly(organophosphazene) was prepared by sequential treatment of poly(dichlorophosphazene) with sodium 4-phenylphenoxide, sodium phenoxide, and sodium trifluoroethoxide in THF. Their substitution percentages were 60, 24, and 16%, respectively. A water-soluble polyphosphazene polyelectrolyte was obtained by sulfonation of aromatic rings by using fuming sulfuric acid. SWNTs were dispersed in an aqueous polymer solution by sonication to give a black homogeneous dispersion. The supramolecular association between the nanotube and the sulfonated polyphosphazene was investigated by TEM, SEM, and AFM. The SEM image of the cleaved edge of the bucky paper, obtained by filtration of the dispersion of SWNTs, showed the nanotubes uniformly wrapped with the polymer. Their diameters were about 30 nm, suggesting small bundles of SWNTs rather than individual SWNTs. Individual SWNTs coated with the polymer were also observed by TEM. The total diameter of the coated tube was about 10 nm and a polymer layer thickness was lager than 4 nm.

Synthetic Approaches to Hydroazulenes and Guaianes through [4 + 3] Cycloadditions of Oxyallyl Intermediates

AbstractBuilding blocks for syntheses of guaiane and secoguaiane sesquiterpenoids were prepared by the title reaction. 4‐(3‐Methylfuran‐2‐yl)butan‐2‐one (1) was obtained in five steps from methyl 3‐methylfuran‐2‐carboxylate (4), and treatment of 1 with pentachloroacetone and sodium 2,2,3,3‐tetrafluoropropoxide in 2,2,3,3‐tetrafluoropropan‐1‐ol produced a [4 + 3] cycloadduct that was dechlorinated without prior isolation to give the oxabicyclic diketone 2 in a low yield. A better route to diketone 2 was via the oxabicycle 10b, prepared in a high yield from 2‐(but‐3‐en‐1‐yl)‐3‐methylfuran (9) and pentachloroacetone, followed by dechlorination. Treatment of 2 with dilute methanolic potassium hydroxide resulted in the cleavage of the oxa bridge, with formation of 3,8‐dimethylazulen‐4‐ol (11). Catalytic hydrogenation of 2 afforded the saturated oxabicyclic diketone 14, intramolecular aldol condensation of which gave the tricycle 15. The oxa bridge of the oxatricyclic enone 15 was cleaved by hydrogenolysis in the presence of palladium/carbon catalyst to give the 6‐hydroxydecahydroazulen‐4‐one 16. Treatment of isobutyl trichloromethyl ketone (20) with furan 9 and sodium trifluoroethoxide in trifluoroethanol eventually gave the 2‐chlorooxabicycle 22. This solvolysis product was dechlorinated to furnish the oxabicyclic trifluoroethoxy ketone 24 as a single product that was subjected to the sequence of transformations used for 10b. X‐ray structure analysis of the resulting saturated diketone 26 established the endo configuration of the isopropyl group. Finally, aldol cyclization of 26 furnished the guaiane derivative 27. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2006)

Telechelic Polyphosphazenes: Reaction of Living Poly(dichlorophosphazene) Chains with Alkoxy and Aryloxy Phosphoranimines

A modification of the method for synthesis of well-defined mono- and ditelechelic polyphosphazenes via the living, cationic polymerization of phosphoranimines has been developed. This process provides access to phosphazene block, comb, and graft copolymers that contain organic or organosilicon macromolecules. Several alkoxy and aryloxy phosphoranimines, RO(CF3CH2O)2PNSiMe3 (R = Ph, MeOPh, C10H7, BOC−NH−CH2CH2, t-BuMe2SiO(CH2)5, C8H11, and CH2CH−C6H4), were synthesized via the reaction between a bromophosphoranimine and the appropriate sodium alkoxide or aryl oxide. These species are potential initiators or terminators, useful for the synthesis of telechelic polyphosphazenes with etheric linkages rather than the amino linkages used previously. Ditelechelic polymers, RO[(CF3CH2O)2PN]n−P(OCH2CF3)3OR, were prepared by terminating living poly(dichlorophosphazene) chains, [Cl3PN−(Cl2PN)n−PCl3]+[PCl6]-, with these alkoxy or aryloxy phosphoranimines. Alternatively, monotelechelic polyphosphazenes were produced through the termination of the polymer [(CF3CH2O2)3PN−(Cl2PN)n−PCl3]+[PCl6]- with the appropriate alkoxy or aryloxy phosphoranimines. In all cases, hydrolytically stable telechelic polymers with controlled molecular weights and low polydispersities were obtained in good yield after macromolecular replacement of labile chlorine atoms with sodium trifluoroethoxide.

Synthesis of Telechelic Polyphosphazenes via the Ambient Temperature Living Cationic Polymerization of Amino Phosphoranimines

A method for the synthesis of well-defined mono-, di-, and mixed-telechelic polyphosphazenes produced via a living cationic polymerization of phosphoranimines is described. Amino phosphoranimines R−NH(CF3CH2O)2PNSiMe3 (R = Ph−, p-BrPh−, p-H3CPh−, CH2CHCH2−, and CH2CHPh−) were synthesized via a reaction between a bromophosphoranimine and the appropriate organic amine. Ditelechelic polymers [R−NH]2−[Cl2PN]n were prepared by quenching living poly(dichlorophosphazene) chains, [Cl3PN(Cl2PN)n−PCl3]+[PCl6]- with small quantities of the amino phosphoranimines. Cationic initiators of the amino phosphoranimines were also generated using PCl5 and were used to polymerize Cl3PNSiMe3, to give monotelechelic poly(dichlorophosphazenes). In addition, a mixed telechelic system was produced by the termination of an allylamino monotelechelic poly(dichlorophosphazene) chain with a bromoanilino phosphoranimine. In all cases, displacement of the chlorine atoms with sodium trifluoroethoxide yielded hydrolytically stable telechel...

Cationic Homo- and Copolymerization of Fluorophosphoranimines as an Ambient Temperature Synthetic Route to Poly(fluorophosphazenes), [NPF(R)]n, with Controlled Architectures

The PCl5-induced polymerization of the fluorophosphoranimine PhF2PNSiMe3 at ambient temperatures (35 °C) yields the poly(fluorophosphazene) [NPF(Ph)]n. This THF-soluble product was treated with an excess of sodium trifluoroethoxide in refluxing dioxane to replace the fluorine atoms by trifluoroethoxy groups and generate the known hydrolytically stable polymer [NPPh(OCH2CF3)]n . The molecular weights in this system can be controlled by variation of the monomer to initiator ratios, and polydispersities for [NPPh(OCH2CF3)]n are in the range of 1.05−1.32. In order to explore the synthetic utility of [NPF(Ph)]n, the polymer was treated with Grignard or alkyllithium reagents such as MeLi, n-BuLi, or p-tolylmagnesium bromide to produce the poly(organophosphazenes) [NPPh(R)]n (R = Me, n-Bu, p-tolyl). Complete replacement of the fluorine atoms using alkyl/aryllithium reagents induced a significant decline in molecular weights. However, treatment of [NPF(Ph)]n with a 0.5 molar equiv of MeLi at −78 °C, followed by replacement of the remaining fluorine atoms with NaOCH2CF3 in refluxing dioxane, produced the mixed-substituent polyphosphazene {[NPPh(OCH2CF3)0.5(Me)0.5]y} with Mn = 2.4 × 104 (PDI = 1.10). The phosphoranimine PhF2PNSiMe3 also reacts at 35 °C with “living” poly(dichlorophosphazene), (NPCl2)n, to produce the block copolymer {[NPCl2]n[NPPh(F)]m}. Halogen replacement by NaOCH2CF3 in refluxing dioxane produced the known hydrolytically stable block copolymer {[NP(OCH2CF3)2]n[NPPh(OCH2CF3)]m} with Mn = 4.5 × 104 (PDI = 1.30).

Regioselective Substitution Reactions of Sulfur(VI)-Nitrogen-Phosphorus Rings: Reactions of the Halogenated Cyclic Thionylphosphazenes [NSOX(NPCl(2))(2)] (X = Cl or F) with Oxygen-Based Nucleophiles.

The reactions of the cyclic thionylphosphazenes [NSOX(NPCl(2))(2)] (1, X = Cl; 2, X = F) with three oxygen-based nucleophiles of increasing basicity, sodium phenoxide (NaOPh), sodium trifluoroethoxide (NaOCH(2)CF(3)), and sodium butoxide (NaOBu) have been studied. The reaction of 1 and 2 with 4 equiv of NaOPh at 25 degrees C yielded the regioselectively tetrasubstituted species [NSOX{NP(OPh)(2)}(2)] (5d, X = Cl; 6d, X = F). Further reaction of 5d with an additional 2 equiv of NaOPh over several days or at elevated temperatures gave the fully substituted compound [NSO(OPh){NP(OPh)(2)}(2)] (5e), whereas 6d did not react further. The reaction of 1 and 2 with 5 equiv of NaOCH(2)CF(3) yielded in both cases [NSO(OCH(2)CF(3)){NP(OCH(2)CF(3))(2)}(2)] (7e), and similarly reaction with 5 equiv of NaOBu yielded [NSO(OBu){NP(OBu)(2)}(2)] (9e). In all cases, the reactions were monitored by (31)P NMR and (where applicable) (19)F NMR and were found to involve complete substitution at phosphorus via a predominantly vicinal pathway, followed by substitution at sulfur. Substitutional control of the reactions of NaOPh, NaOBu, with 1 and 2 was found to conform to the following general order of reactivity, PCl(2) > PCl(OR) > SOX (X = Cl, F). Although the reaction with NaOCH(2)CF(3) followed the same order of reactivity, a significant enhancement of reaction rate was detected with each equivalent of trifluoroethoxide added. Reaction of 7e with excess NaOCH(2)CF(3) led to elimination of (CF(3)CH(2))(2)O and the formation of the salts Na[NSO(OCH(2)CF(3))NP(OCH(2)CF(3))(2)NP(OCH(2)CF(3))O] (11) and Na[NS(O)O{NP(OCH(2)CF(3))(2)}(2)] (12). Crystals of 6d are triclinic, space group P&onemacr;, with a = 9.789(3) Å, b = 11.393(4) Å, c = 12.079(5) Å, alpha = 107.40(3) degrees, beta = 91.23(3) degrees, gamma = 93.18(3), V = 1283.6(8) Å(3), and Z = 2. Crystals of 5e are monoclinic, space group C2/c, with a = 32.457(3) Å, b = 10.747(1) Å, c = 18.294(2) Å, beta = 110.37(1) degrees, V = 5982.4(9) Å(3), and Z = 8.

Poly(monophosphazophosphazenes): New Polymers with N:PR3 Side Groups

Phosphazene high polymers with N=PR 3 (phosphazo) side groups were prepared with trifluoroethoxy, phenoxy, anilino, and propylamino side groups. Small-molecule cyclic counterparts were also synthesized as model systems for the macromolecular inactions. These compounds were prepared using both (trichlorophosphazo)pentachlorocyclotriphosphazene (N 3 P 3 Cl 5 NPCl 3 ) and (trichlorophosphazo)pentafluorocyclotriphosphazene (N 3 P 3 F 5 NPCl 3 ) as the starting materials. Specifically, the synthesis of monophosphazophosphazene polymers through the thermal ring-opening polymerization of N 3 P 3 Cl 5 NPCl 3 at 150-180°C or of N 3 P 3 F 5 NPCl 3 at 200-210°C is reported. Differences in the reactivity of the phosphazochloro- and the phosphazofluorophosphazenes to halogen replacement reactions were found at both the cyclic trimeric and high polymeric levels. In general, replacement of the chlorine atoms by organic groups was achieved with greater ease than the replacement of fluorine atoms. For the reagents studied, the replacement of halogen atoms by sodium trifluoroethoxide was more facile than with the other nucleophiles. A comparison is made between the properties of monophosphazophosphazenes, classical phosphazenes, and 1,1-diphosphazophosphazenes

Reactivity and polymerization behavior of a pentachlorocyclocarbophosphazene, N3P2CCl5

The cyclic carbophosphazene N 3 P 2 CCl 5 reacts with sodium methoxide, sodium trifluoroethoxide, and sodium phenoxide to yield the corresponding pentaalkoxy- and pentakis(aryloxy)cyclocarbophosphazenes. By contrast, N 3 P 2 CCl 5 does not react with the main group and transition metal nucleophiles lithium diphenylphosphide and lithium pentacarbonylmanganate and reacts incompletely with sodium dicarbonyl(η 5 -2,4-cyclopentadien-1-yl)ferrate

Synthesis and thermal reaction of acetylenic group substituted poly(organophosphazenes) and cyclotriphosphazene

Poly(bis[4-([trimethylsilyl]ethynyl)anilino]phosphazene) was prepared by reaction of poly-(dichlorophosphazene) with 4-[(trimethylsilyl)ethynyl]aniline. Cosubstituent poly(organophosphazene)s were synthesized by sequential reaction of poly(dichlorophosphazene) with 4-[(trimethylsilyl)ethynyl]aniline and sodium trifluoroethoxide. Trimethylsilyl groups were removed by treating the polymers with aqueous KOH in methanol to give acetylene-substituted polyphosphazenes. These polymers were soluble in common organic solvents and thermally curable under moderate conditions