Water-THF mixtures

Katz, Lochmuller and Scott also examined acetonitrile/water, and tetrahydrofuran (THF)/water mixtures in the same way and showed that there was significant association between the water and both solvents but not nearly to the same extent as methanol/water. At the point of maximum association for methanol, the solvent mixture contained nearly 60% of the methanol/water associate. In contrast the maximum amount of THF associate that was formed amounted to only about 17%, and for acetonitrile the maximum amount of associate that was formed was as little as 8%. It follows that acetonitrile/water mixtures would be expected to behave more nearly as binary mixtures than methanol/water or THF/water mixtures. 

Figure 2.12 OATS phase separation of a THF-water mixture (left) containing dodecanethiol-stabilized gold nanoparticles. Pressurization of the mixture with C02 induces a phase separation where the nanoparticles remain in the C02-expanded THF (right).

Conversion of 2 ,4, 6 -trihydroxyacetophenone to the tricarbonate proceeded smoothly in 87% yield on treatment with 3.3 equivalents of methyl chloroformate and triethylamine in THF at 0°C. Treatment of this tricarbonate with 4 equivalents of sodium borohydride in a 1 1 THF/water mixture at 0°C to ambient temperature gave the phenol 1 in 83% yield. 

In order to investigate the effect of the ring substitution on preferential adsorption of water in poly(phenyl methacrylate) derivatives, it has been studied the preferential adsorption behavior of poly(2,4 - dimethylphenyl methacrylate) (2,4 - DMP), poly(2,5 - dimethylphenyl methacrylate) (2,5 - DMP) and poly(3,5 -dimethylphenyl methacrylate) (3,5 - DMP) in THF/water mixtures [109],... 

First the capillary is treated with a pH 10 ammonia solution (6 mM) for 20 h at a flow rate of 0.1-0.2 mL/h. The capillary is then rinsed with deionized water followed by a wash with 0.1 M HC1 and then a second rinsing with water. The tube is next dried with nitrogen, filled with dioxane and then flushed with a 1.0 M TES solution in dioxane containing HC1 as a catalyst for 90 min at 90°C. After the TES treatment, the capillary was washed with tetrahydrofuran (THF) for 2 h and then with a 1 1 THF-water mixture for 2 h. The capillary is then dried with a flow of nitrogen gas for 0.5 h. The capillary, which now has a hydride surface, is then flushed with dry toluene in preparation for the second modification. 

Kobayashi examined the efficacy of various silver salts (e.g., AgOTf, AgC104, Ag2C03) as catalysts for the aza-Diels-Alder cycloaddition of 195 to imines formed in situ in a 9 1 THF/water mixture (Scheme 2.51).84 The silver salts with basic anions (e.g., Ag2CQ3) were unable to catalyze the reaction, but the silver salts with nonbasic... 

For a particular solute, a capacity factor of 3 may be found in a 50/50 mixture of methanol and water. For the same solute, a mixture of 34 %THF in water may also yield a capacity factor of 3. For a different solute, the capacity factor in a 50/50 methanol/water mixture may be 30, and the same capacity factor may be observed with a 28/72 THF/water mixture. The average composition for many solutes that yield the same capacity factor as the 50/50 methanol/water mixture yields the (average) experimental point on the solid line for THF at

[Pg.65]

Next, the concept of iso-eluotropic mobile phases is used to determine the binary acetonitrile-water and THF-water mixtures that correspond to the initial and the Final composition. For example, 20% methanol corresponds [627] to 17% acetonitrile and to 12% THF, whereas 100% methanol corresponds to 84% acetonitrile and to 59% THF. 

The final step of the sequence is the saponification of the esters endo-18 and exo- %. Methyl esters are relative inert to basic conditions and so lithium hydroxide in THF/water mixtures is often used for saponifications. The resulting acids endo-S and exo-S are obtained as 3 1 mixture of diastereomers. 

The total synthesis of the antiviral marine natural product (-)-hennoxazole A was accomplished by F. Yokokawa and co-workers." The mild reduction of a secondary alkyl azide at C9 was carried out using triphenylphosphine in a THF/water mixture at slightly elevated temperature. The corresponding primary amine was obtained in good yield and was subsequently acylated and converted to one of the oxazole rings of the natural product. 

The stereoselective total synthesis of tt)-campherenone was accomplished by T. Uyehara and co-workers based on a photochemical Wolff rearrangement. The bicyclic ketone was treated with 2,4,6-triisopropylbenzenesulfonyl azide (trisyl azide) under homogeneous basic conditions and the a-diazo ketone was obtained in excellent yield. The photochemical rearrangement of the diazo ketone was conducted in a THF-water mixture using a high-pressure 100 W mercury lamp. The ring-contracted acid was isolated as a 4 1 mixture of endo and exo products. 

Solid-state NMR also allows for the study of sample preparation effects on the local cation environment. Na-SPS with 1.7% styrene sulfonate groups cast from dimethyl formamide or tetrahydrofuran (THF)/ water mixtures shows more aggregated ions, i.e., a more intense peak at 20 ppm, than ionomers cast from less... 

Polymerization in a single-phase homogeneous solution in THF/water mixtures (2 1) has also been reported [235]. Such reactions allowed for the preparation of a poly (p-phenylene) with sulfonate ester and dodecyl side groups [Eq. (10)]. By comparison to the aforementioned biphasic polymerizations, the synthesis of polymers with higher degrees of polymerization was reported in the solution procedure. 

In methanol-water mixtures where ESPT is observed already in the absence of water, we separated the methanol- and water-dependent components of the proto-lytic dissociation rate constant for several photoacids [41]. As in THF-water mixtures, the water-dependent component has a power-law dependence on water concentration. The magnitude of the exponent decreased with the increase in photoacid strength. 

Fortunately, we were able to regioselectively tosylate the primary hydroxyl in 42 with p-toluenesulfonyl chloride, triethylamine, and DMAP in dichloromethane at room temperature over 14 h tosylate 63 was isolated in 85% yield. The subsequent nucleophilic displacement with iodide also proceeded satisfactorily delivering the 6-deoxy-6-iodopyranoside 41 in 92% yield. With the desired 6-iodo sugar successfully prepared, we examined its Vasella reductive ring cleavage with Zn dust (size <10 pm) in a 4 1 THF / water mixture at reflux (Scheme 13). A single product was formed according to TLC analysis. However, our H-NMR examination of this product revealed that it was in fact a 1 1 mixture of the two anomeric hemiacetals 40a and 40P formed in 80% yield. 

The similar dependence of S on A/ for polystyrene solutes (46) can be explained by the use of a poor-solvent mot e phase (THF/water mixtures), with a resulting tendency of the polystyrene molecuks to assume a more collapsed structure. In either case (proteins or polystyrenes), the solute molecule appears to resist complete unfolding in sorM state. In... 

The desire for a more environmentally friendly oxidizing agent prompted the synthesis of water-soluble derivatives of IBX. This water-soluble oxidant m-IBX (eq 7) contains a carboxylic acid substituent. This reagent is useful for the oxidation of a variety of alcohols to the corresponding aldehydes in both water and THF/water mixtures in fair-to-excellent yields. ... 

Alternatively, if such azides bear a l°-benzylic group they can be converted to A-methylanilines by reaction with EtsSiH and SnCl4. Wilkinson s catalyst and Et3SiH reduce aromatic nitro groups to their amines in moderate to good yields, while the combination of Pd(OAc)2 and EtsSiH in a THF-water mixture reduces aliphatic nitro groups to the A-hydroxylamines (eq 25). ... 

Chemical polymerisation of the monomers (3a) and (3b) were conducted by addition of 4 mol-equiv. of anhydrous FeCl3 in chloroform to a stirred solution of the respective monomers under dry nitrogen atmosphere. The reaction was allowed to continue for 2 hours at 25 °C and polymer products isolated by filtration, rinsed with deionised water and dried in vacuo. The undoped polymers were obtained by stirring the respective doped polymers in THF/water mixture for 4 hours and filtered. 

Apart from triarylindiums, diarylindium halides and arylindium dihalides, stable in an aqueous media, smoothly react with aryl iodides and bromides at a very low palladium-catalyst loading in a THF / water mixture (8 1 to 6 1, v/v) to give the biaryls in very high yields tolerating free-amino, hydroxy, carboxy groups, as well as aldehyde, nitro group, etc. The presence of a polar cosolvent (water) has been essential... 

The large increase in rate and decrease in activation energy for base hydrolysis of the tetraphenylphosphonium cation as the proportion of the organic component increases in THF-water mixtures is attributed to a combination of initial-state desolvation and transition-state stabilization. It is claimed that something like 13 water molecules have to be removed from the solvation shell in going from the initial to the transition state. The results from this study are discussed in relation to those from earlier studies involving the co-solvents acetone, dioxan, and DMSO. 

Figure 5.18 Fluorescent photographs of (A) DDPD (10 pM) and (B) HPS (10 pM) in THF-water mixtures with different water fraction ff) upon UV illumination. Adapted from ref. 70 with permission from the Royal Society...

Figure 5.20 (A) Structures of AIE-active TPE unit modified traditional FBI dye and the polymer matrix DSPE-PEG2000 and DSPE-PEG5000-folate. (B) Photoluminescence properties of BTPEPBI in THF-water mixtures with different water fraction (, ) excited at 538 nm. (C) Particle size of the BTPEPBI-encapsulated organic nanoparticles. (D) In vitro cell imaging stained by BTPEPBI-NPO (left) and BTPEPBI-NP50 (right) for 2 h at 37 C (E) in vivo FL imaging of H22 tumor-bearing (red circle) mice after intravenous injection of BTPEPBI-NPO (left) and BTPEPBI-NP50 (right) respectively. Adapted from ref. 79 with permission from the Royal Society of Chemistry.

Figure 5.23 (A and B) Schemes and structures of NIR AIE molecule QM-2 and QM-5 derivatives. (C) Photoluminescence properties of QM-2, QM-5 in THF-water mixtures with different water fraction (f,). (D) SEM and TEM imaging of QM-2 and QM-5 aggregates used for in vitro cell imaging. (E) In vivo non-invasive imaging of tumor-bearing mice after intravenous injection of QM-2 and QM-5 at different time periods (0.5,1.5, 3, and 24 h). (F) TEM imaging of HeLa cells and tissues exposed to the QM nanoprobes. Adapted from ref. 87 with permission from John Wiley and Sons. Copyright 2015 Wiley-VCH Verlag GmbH Co. KGaA, Weinheim.

Very recently the combination Bi[III]/Al was applied in a THF/water mixture for a one-step carbon-carbon bond formation reaction in the synthesis of amines [134]. Benzyl bromide as well as iodomethane were used as the halides ... 

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