Benzyltrimethylammonium hydroxide 3-effect

Temperature Effects. The oxidation of 9,10-dihydroanthrafcene to anthraquinone in anhydrous pyridine solvent with benzyltrimethylammo-nium hydroxide as the base occurs over a wide temperature range (Table I). Some oxidation takes place at a temperature as low as — 20°C., but maximum anthraquinone conversions (about 70%) occur between 50° and 70°C. Above 70°C., the conversion decreases, probably as a result of thermal decomposition of the benzyltrimethylammonium hydroxide. 

The phase transfer catalyzed alkylation reaction of dodecyl phenyl glycidyl ether (DPGE) with hydroxyethyl cellulose (HEC) was studied as a mechanistic model for the general PTC reaction with cellulose ethers. In this way, the most effective phase transfer catalysts and optimum reaction concentrations could be identified. As a model cellulose ether, CELLOSIZE HEC11 was chosen, and the phase transfer catalysts chosen for evaluation were aqueous solutions of choline hydroxide, tetramethyl-, tetrabutyl-, tetrahexyl-, and benzyltrimethylammonium hydroxides. The molar A/HEC ratio (molar ratio of alkali to HEC) used was 0.50, the diluent to HEC (D/HEC) weight ratio was 7.4, and the reaction diluent was aqueous /-butyl alcohol. Because some of the quaternary ammonium hydroxide charges would be accompanied by large additions of water, the initial water content of the diluent was adjusted so that the final diluent composition would be about 14.4% water in /-butyl alcohol. The results of these experiments are summarized in Table 2. 

The best alkylation efficiencies of DPGE were obtained with benzyltrimethyl- and tetrabutylammonium hydroxide. To explore the effect of the variation of A/HEC ratio on DPGE alkylation efficiency, experiments were conducted at varying A/HEC ratios (see Figure 3). The alkylation efficiency maximum occurs between about 0.25 and 0.50 A/HEC molar ratio. The observed alkylation efficiencies of DPGE with tetrabutylammonium hydroxide were comparable to the alkylation efficiencies with benzyltrimethylammonium hydroxide. 

Shechter and Wynstra ( ) also demonstrated that benzyldi-methylamine was a somewhat more effective catalyst than potassium hydroxide, and the quaternary compound benzyltrimethylammonium hydroxide was even more powerful. Each reaction was highly selective. 

Racemization via a reversible addition/elimination process under mild conditions can be used, with for example cyanohydrins, hemiacetals, hemiaminals and hemithioacetals. SiUca-supported benzyltrimethylammonium hydroxide (BTAH) was used to racemize cyanohydrins and effected an efficient DKR process in tandem with porous ceramic-immobilized lipase (lipase PS-C II) (Scheme 4.22) [57]. 

In their initial studies, Shechter and Wynstra had demonstrated that these catalysts could achieve high selectivity of the epoxy-phenol reaction in a solution of excess phenol. They later reversed the situation and studied the reaction selectivity in a solution of excess glycidyl ether in which the phenol was used as the limiting reagent. The excess of epoxide over phenol was measured until phenol had practically disappeared, and the results in all cases indicated high selectivity towards the epoxy-phenol reaction. The tertiary amine, ben ldimethylamine, was somewhat more effective than potassium hydroxide benzyltrimethylammonium hydroxide was even more powerful. First-order kinetics were observed for all reactions. Since it was postulated that the phenoxide ion was common to all these reactions, the observed diffCTences in reaction rates were linked to the cation. In was not determined, however, whether the cation effect is one of different degrees of dissociation of the phenol salts or of some other phenonomenon. 

In 1995, Ando reported that a,p-unsaturated esters could be obtained with high Z selectivity from the HWE reaction of aldehydes with diphenylphosphonoacetates in the presence of benzyltrimethylammonium hydroxide (Triton B) or NaH in tetra-hydrofuran [182], Later, Ando [183-186], Motoyoshiya [187, 188], and Touchard [189, 190] further defined this protocol by modifying diphenylphosphonoacetates and found that the employment of bis(o-alkylphenyl)phosphonoacetates led to higher Z selectivity (Scheme 39). The combination of NaH and Nal has been identified as an effective base/additive system to improve the Z selectivity [191]. Moreover, the Ando modification has recently been applied to the ring closure of various macrolides with high Z selectivity, which is complementary to that of traditional intramolecular HWE reaction (Scheme 40) [192, 193]. 

Benzyldimethylamine has been found to be somewhat more effective than potassium hydroxide, and the quaternary compounds such as benzyltrimethylammonium hydroxide have been found to be even more powerful. 

Only a few departures from the basic Haloform reaction conditions (Section 7.3.5) have been developed. Both sodium bromite23 and benzyltrimethylammonium tribromide24 in aqueous sodium hydroxide are convenient alternatives to the use of bromine in the Haloform reaction (e.g., 13 to 14,23 15 to 1624). Both reagents also effect conversion of methyl carbinols to carboxylic acids. 

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