Tetrabutylammonium halide

In our previous works[8,9] on the synthesis of various 5-membered cyclic carbonate, quaternary ammonium salts such as tetrabutylammonium halides showed excellent catalytic activities in relatively mild reaction conditions, under atmospheric pressure and below 140 U. hi this work, several kinds of quaternary ammonium salts have been used for the transesterification reactions of the ethylaie carbonate with methanol to DMC and ethylene glycol. 

There are a number of industrially important reactions where two liquid phases are involved and the aqueous phase contains ionic species. Here the rate may be severely limited due to low solubiblity of the reactant, located in the organic phase, in water. We would benefit from using a pha.se-transfer (PT) catalyst, which ferries the ionic species into the organic phase thus overcoming a severe limitation. Such PT catalysts are typically quaternary ammonium compounds like tetrabutylammonium halides, trioctylmethylammonium chloride, etc. (see also Section 3.8). 

If one of the species is anionic and we need to transport it to the organic phase, then a phase-transfer catalyst may be employed. Consider the example of benzyl penicillin where the reaction between phenyl acetic acid and the penicillin carboxylate ion, with penicillin amidase as a catalyst, is relevant, and which at pH 4.5 - 5.0 is shifted in the desired direction. Here a catalyst like tetrabutylammonium halide works, and with chloroform as a solvent 60% yield can be realized in contrast to a yield of only 5 - 10 % in water. 

The phase-transfer catalyst (Q+X-) is usually a quaternary ammonium halide (R4N+X ) such as tetrabutylammonium halide (CH3CH2CH2CH2)4N+X. ... 

Figure 5. The complexation of phenylhalocarbenes with tetrabutylammonium halides in CH3CN. The numbers in parentheses are gas phase proton affinities.

Recently a porphyrin unit has been incorporated into an anion receptor (Fig. 46) (Beer et al., 1995g). H nmr titration experiments with this compound demonstrated the formation of 1 1 stoichiometric complexes with tetrabutylammonium halides, nitrate, hydrogensulfate and dihydrogenphosphate. 

A compound whose addition to a two-phase organic water system helps to transfer a water soluble ionic reactant across the interface to the organic phase where a homogeneous reaction can take place is called a phase transfer catalyst. These catalysts enhance the rate of a reaction. A quaternary ammonium halide R4N+ X- e.g., tetrabutylammonium halide is phase transfer catalyst. It can cause the transfer of the... 

With the original protocol, attempted threefold couplings of even a 4-nitro-substituted 1,2,3-triiodobenzene derivative failed.However, under the modified conditions of Jeffery, that is, with a base like potassium carbonate in the presence of a tetrabutylammonium halide, multifold Heck couplings of oligohaloarenes are brought about in very good yields (Schemes 5 and... 

The triflate 5 (0.593 g, 1.70 mmol) was combined with the appropriate tetrabutylammonium halide (3.34 mmol) in 30 mL of anhydrous benzene and heated at reflux for 2 h. Alter cooling to room temperature, the benzene was removed under reduced pressure. The residue was dissolved in the minimum amount of dichloromethane, chromatographed on a 2.5 x 10 cm column of 230—400 mesh silica gel with a 3 2 ratio of ethyl ether/hexane... 

The effect of the anion on the copolymerization rate is controversial. Hilt et al.41 established for different sodium halides the following order of efficiency F < Cl < Br < J . This order was interpreted on the basis of the increase in nucleophilicity or polarizability of the anions. Sfluparek and Mleziva 43) observed that the reaction rate of the benzoate anion was about twice as high as that of the bromide anion in the copolymerization of epichlorohydrine with phthalic anhydride. On the other hand, Luston and Manasek56) did not detect any effect of the anion size on the copolymerization rate initiated by tetramethylammonium and tetrabutylammonium halides. 

Detailed studies on the UV absorption spectra of alkenyl-A3-iodane 133 (X = Cl,Br,I) in acetonitrile solutions in the presence of tetrabutylammonium halides show the equilibrium formation of the iodate 134 (Sect. 2.1), in addition to the iodonium ion 132 coordinated by acetonitrile via hypervalent bonding. [Eq. (116)] [213]. The equilibrium constants are summarized in Table 5. Determinations of the equilibrium constants by UV spectra were carried out at a low concentration of the A3-iodane (<10 4 M), without considering the formation of the corresponding dimers. The magnitudes of the equilibrium constant K1 clearly decrease in the order Cl >Br >1, which reflects the differences in the stability of alkenyl-A3-iodane 133. 

Studies of the conversion of ( )-jS-alkylvinyl(phenyl)iodonium tetrafluorob-orates to (Z)-haloalkenes (complete inversion) with tetrabutylammonium halides (Cl", Br", I") in acetonitrile provide convincing evidence for the vinylic... 

Conditions of Heck reactions with alkenes have been made considerably more mild through the addition of tetrabutylammonium halides and weak bases such as KOAc or K2C03. The reagents have been employed in polar aprotic solvents such as DME, or under phase transfer conditions in their presence, yields are often increased and, in the case of iodides, reactions may be accomplished even at room temperature285-288. 

Alkylation requires more vigorous conditions. These reactions were originally performed on the stannylene acetal with the alkylating reagent in DMF at elevated temperatures (45°C for methyl iodide or 100°C for benzyl bromide)66 or on the tributylstannyl ether in neat benzyl bromide or allyl bromide at 80-90°C.67 It was then discovered that the presence of added nucleophiles markedly accelerates the reactions, so that alkylation of both tributylstannyl ethers and dibutylstannylene acetals in benzene, which is very slow at reflux with benzyl bromide alone, occurs at a reasonable speed at reflux in the presence of added tetrabutylammonium halides.57,63 Many other nucleophiles are also effective, including A-methylimidazole68 and... 

To a solution of the geni-bis(triflate) (10 mmol) in CHjCU (100 niL) at O C was slowly added a solution of [Bu4N] [Ph3SnF2] (10 mmol) in CHjClj (50 mL). After 4 h (8 h for a-branched aldehydes) the mixture was filtered and the appropriate tetrabutylammonium halide (20 mmol) added. After stirring for 1 h at rt the solvent was evaporated at reduced pressure and the crude mixture filtered through a short (10 cm) column of silica gel. Pure products were obtained by column chromatography (silica gel. pentane). 

Unlike lithium halides, tetrabutylammonium halides are fully dissociated in PDC, but they are associated in HMPA, and this is in agreement with simple electrostatic considerations. Similar results have been found in DMF, where alkali metal halides are fully dissociated whereas tetraaUcylammonium halides are associated 56, 57). 

Tributyltin bromide or iodide and dibutyltin dibromide or diiodide can be prepared from the corresponding chlorides by reaction with alkyl bromides or iodides in the presence of a tetrabutylammonium halide catalyst. It is suggested that the reaction involves the coordination of halide ion to the tin, then nucleophilic substitution by the chloride ligand at the carbon centre (equations 11-18,11-19 and 11-20).35... 

Ochiai and co-workers first discovered that the nucleophilic substitution of (E )-l-alkenyl(phenyl)iodonium tetrafluoroborates (e.g., 11) with tetrabutylammonium halides (except with fluoride) in various solvents at room temperature occurs with complete inversion of configuration to give (Z)-l-haloalkenes (e.g., Z-12) (Scheme... 

The regioselectivity of arylation of the electron-rich olefin, n-butylvinyl ether with 4-nitrophenyl triflate has been investigated129. Without added lithium salt the regioselectivity was low (fr.a = 1.5) whereas addition of a lithium halide in DMF strongly promotes / -arylation (p/oc =13) and addition of tetrabutylammonium halide in CH3CN gave a somewhat lower regioselectivity (P/[Pg.932]

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