TBA carboxylates

It would be of interest to see if the more stable cesium carboxylates would be better catalysts for GTP than TBA carboxylates since Quirk showed that cesium 9-methylfluorenide works as well as TBA 9-methylfluorenide as a catalyst in his mechanism studies [6]. 

Analogous information on TBA carboxylate and dicarboxylate polyhyd-rates is presented in this issue, p. 259,... 

The binary aqueous systems phase diagrams in the range of the crystallization of TBA carboxylate and isocarboxylate polyhydrates are given in Figures 1 and 2 respectively, and some properties of the hydrates are shown in Table I. Two hydrates with stable crystallization branches form in the TBA acetate - water system. One stable and several metastable hydrates have been discovered in each of the rest of the systems (from 1 (TBA formate) to 8 (TBA o-butyrate)). 

We have just come across and read the article by H. Nakayaroa and Sh. To-rogata (Bull.Chem.Soc.Jpn., 5Zr 171 (1984)), whose results do not contradict ours. The authors have studied 19 TBA carboxylate - water systems and have discovered one hydrate in each system. The melting points and... 

Figure 4. The dependence of the melting points of the hyoraxes on the anion length a) TBA carboxylates, b) TBA dicarboxylates. n - the number...

The tert-huty hydroperoxide is then mixed with a catalyst solution to react with propylene. Some TBHP decomposes to TBA during this process step. The catalyst is typically an organometaHic that is soluble in the reaction mixture. The metal can be tungsten, vanadium, or molybdenum. Molybdenum complexes with naphthenates or carboxylates provide the best combination of selectivity and reactivity. Catalyst concentrations of 200—500 ppm in a solution of 55% TBHP and 45% TBA are typically used when water content is less than 0.5 wt %. The homogeneous metal catalyst must be removed from solution for disposal or recycle (137,157). Although heterogeneous catalysts can be employed, elution of some of the metal, particularly molybdenum, from the support surface occurs (158). References 159 and 160 discuss possible mechanisms for the catalytic epoxidation of olefins by hydroperoxides. 

Method B The potassium salt of the carboxylic acid (11 mmol) is shaken with TBA-Br (0.1 mmol) or Aliquat (0.3 mmol) for 5 min. The haloalkane (10 mmol) is added and the mixture shaken for a further 5 min, and then allowed to stand (see Table 3.8). The mixture is filtered and Et20 (50 ml) is added. The solution is filtered through silica (5 g) and evaporated to yield the ester. 

Method C (with microwave irradiation) The alkylating agent (10 mmol) and TBA-Br or Aliquat (1 mmol) are mixed with the potassium carboxylate (10 mmol) and then placed in a microwave oven (600 W) for 2-7 min. On completion of the reaction, CH2C12 (50 ml) is added. The crude mixture is filtered through Florisil and the filtrate is evaporated to yield the ester. 

The acid fluoride (3 mmol), obtained from the carboxylic acid and cyanuric fluoride, and TBA-F (5 mg, 0.02 mmol) are added to the silylamine (3 mmol) in MeCN (5 ml) under N2 and the solution is stirred for 6 h at room temperature. The solvent is removed under reduced pressure and the residue is taken up in CH2Cl2. The organic solution is washed with aqueous NaHCO, (5%, 2 x 10 ml), aqueous HCI (4M, 2 x 10 ml) and H20 (20 ml), dried (Na2S04), and evaporated to yield the amide (>75%). 

The preferred catalysts for GTP are nucleophilic anions. The most active catalysts are fluorides and bifluorides [1]. At above ambient temperatures, however, carboxylates and bicarboxlates are preferred [11]. A large counter ion is required for maximum efficiency. In the early work trisdimethylaminosul-fonium (TAS) was used, but later the more readily available tetrabutylam-monium (TBA) salts have gained favor. Since TBA slowly decomposes under the basic conditions used for GTP, other positive ions may work better. Quirk used cesium ion for his mechanistic studies and found it to be equivalent to TBA [6]. Bywater worked with the very stable Ph3PNPPh3+ bifluoride in his mechanistic probes [19] and Jenkins [21] showed that potassium com-plexed with 18-crown-6 was a possible alternative to TBA (Scheme 10). 

A new type of copolymer resist named ESCAP (environmentally stable chemical amplification photoresist) has recently been reported from IBM [163], which is based on a random copolymer of 4-hydroxystyrene with tert-butyl acrylate (TBA) (Fig. 37), which is converted to a copolymer of the hydroxystyrene with acrylic acid through photochemically-induced acid-catalyzed deprotection. The copolymer can be readily synthesized by direct radical copolymerization of 4-hydroxystyrene with tert-butyl acrylate or alternatively by radical copolymerization of 4-acetoxystyrene with the acrylate followed by selective hydrolysis of the acetate group with ammonium hydroxide. The copolymerization behavior as a function of conversion has been simulated for the both systems based on experimentally determined monomer reactivity ratios (Table 1) [164]. In comparison with the above-mentioned partially protected PHOST systems, this copolymer does not undergo thermal deprotection up to 180 °C. Furthermore, as mentioned earlier, the conversion of the terf-butyl ester to carboxylic acid provides an extremely fast dissolution rate in the exposed regions and a large... 

The acid (1,3,4-TBA) (6.90) is attached to the metal by a single carboxylic function, the plane of the aromatic ring making an angle of 25° with respect to the perpendicular to the surface. The two other carboxylic functions are involved in the formation of a hydrogen-bonded network at the metal surface. This 2D network forms two enantiomeric domains for which the [Oil] axis is the mirror (Figure 6.67). 

Figure 5 Separation of carboxylates as ion pairs with tetra-butylammonium (TBA) A, absorbance. Stationary phase LiChrosorb RP8, lOpm. Mobile phase TBA 3.2 x 10" moll" in acetonitrile-phosphate buffer, pH 6.0 (20 + 80). UV detection at 254 nm. Peaks 1, 4-hydroxybenzoic acid 2, 3-hydroxbenzoic acid 3, acetylsalicylic acid 4, benzoic acid. (Reprinted with permission from Tilly-Melin A, Askemark Y, Wahlund K-G, and Schill G (1979) Analytical Chemistry 5 976-983 American Chemical Society.)...

Recently, the cosolvent system of tertiary alcohols such as fert-butanol, ferf-amylalcohol, and acetonitrile has shown very promising results for F-fluorination in the presence of TBA" ((C4H9)4N ) salts, e.g., hydroxide or carbonate (Kim et al. 2006). Other functionalities with acidic protons (e.g., hydroxyls, phenols, thiols, or amides) or nucleophilic character (e.g., amines, carboxyls) have to be protected. Side products formed by elimination or the formation of the corresponding alcohols by hydrolysis of the high excess of precursor may coelute during HPLC purification and thus contaminate the product (pseudo carrier). 

Fabbrizzi and coworkers have synthesized a naphthalimide-substituted urea capable of double depro-tonation. The addition of TBA-F to 122 in DMSO leads to a yellow to red color change after the addition of a few equivalents of anion, and on further addition, a second deprotonation step occurs leading to a blue coloration. This process can be monitored by UV-vis spectroscopy with the emergence of a new band at 540 nm for the single deprotonated species and a decrease in the free host band at 400 nm. With further addition of F , a new band at 600 nm forms corresponding to the doubly deprotonated species, with a decrease in the band intensity at 540 nm (Figure 32). Isosbestic points are observed for all new bands showing a clear transition between species. Carboxylates such as acetate also lead to a similar effect. 

Anion receptors that lack the ability to form soft materials can form dimension-controlled organized structures by combining with anionic species possessing aliphatic units. A combination of la, b with gallic carboxylates with long alkyl chains (Ar C02 , n = 16, 18, and 20, Figure 4.9a) provided mesophases, consisting mainly of lamellar structures, with transition temperatures of 42, 56, and 103 67, 73, and 101 and 67, 81, and 96°C for la Ar = C02--TBA- -(n = 16, 18, and 20, respectively) and 40, 61, and 81 53, 64, and 86 and 61, 82,... 

Alkylation can be used to prepare amphiphilic HA derivatives. Alkylation of HA carboxylic groups can be performed using HA-TBA salt and alkyl halides, such as alkyl iodides or bromides, in an organic solvent [34, 35]. Alkylation of HA is also performed in an aqueous environment by using adipic dihydrazide modified HA and 1-decanal [36]. 

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