TEBA

In the mid-1960s a series of papers by Makosza and Serafinowa (1965, 1966) appeared under the common title Reactions of Organic Anions , in which the catalytic alkylation of phenylacetonitrile and its derivatives carried out in the presence of concentrated NaOH and the catalyst triethylbenzylammonium chloride (TEBA) was described. This was the beginning of phase-transfer catalysis (PTC), and since then thousands of papers haven been published on the subject. 

Rapid N-alkylation of saccharin (Eq. 24) by a series of halides was performed on silica gel via its sodium salt in a microwave oven. TEBA was shown to have a useful co-catalytic effect (Tab. 5.11). 

Tab. 5.14 Alkylation of phenylacetonitrile under MW + PTC conditions (NaOH 6 equiv.,TEBA 15%).

SOCl2 (208 g, 1.75 mol) is added in one portion to a refluxing solution of TEBA-Cl (0.27 g, l. 2 mmol) and the acid (0.826 mol) in Cl(CH2)2Cl (l. 5 l). The solution is refluxed for a further period of time, and then filtered hot and evaporated to yield the acid chloride, which is purified, if necessary, by chromatography from silica [e.g. trans-cyclohexane-1,4-dicarbonyl chloride (30 min), 96% naphthalene-2,6-dicarbonyl chloride (12 h), 94% biphenyl-4-carbonyl chloride (25 min), 60% biphenyl-4,4 -dicarbonylchlo-ride (16 h), 90%]. 

Powdered KOH (0.17 g, 3 mmol) is added to the freshly prepared thioiminium halide [MeC(SR)NH2+Cl- or McC(SR)NMc2+C1 ] (3 mmol) and TEBA-C1 (0.12 g, 0.5 mmol) in CH2C12 (30 ml). The mixture is stirred at room temperature until the reaction is complete, as shown by TLC analysis. The organic phase is separated, washed with H20 (2 x 25 ml), dried (Na2S04), and the solvent evaporated under reduced pressure to yield the alkyl aryl thioether and the dialkyl disulphide, which can be separated by chromatography from silica. 

The aryl diazonium tetrafluoroborate (4 mmol) is added portionwise over ca. 20 min to (TEBA)2-MoS4 (2.69 g, 4.4 mmol) in dry MeCN (10 ml) at 0°C. The mixture is stirred at 0°C for 1 h and then at 25°C for ca. 5 h. The solvent is removed under reduced pressure and the residue is extracted with Et20 (5 x 30 ml). The ethereal extracts are evaporated and the product purified by chromatography from silica to yield the diaryl disulphide. 

Method A Aqueous NaOH (50%, 15 ml) is added portionwise to the appropriate phenylacetonitrile (50 mmol), the chloronitrobenzene (50 mmol), and TEBA-Cl (0.23 g, l mmol) in PhH (10 ml) (the solvent can be omitted with liquid chloronitrobenzenes). The mixture is stirred vigorously at 40-50°C for 3-4 h and then diluted with H20 (25 ml). The aqueous phase is separated, extracted with PhH (2 x 10 ml), and the combined PhH solutions are dried (MgS04) and evaporated to yield the product. 

H202 (30%, 6 ml) is added with stirring to the alkene (50 mmol) and TEBA-Cl (0.1 g, 0.44 mmol) in CC14 (10 ml) and CaCl2 or CaBr2 (50 mmol) in cone. HC1 or HBr (10 ml) at 0°C. The mixture js allowed to come to room temperature and is stirred for a further 20 min. Petroleum ether (50 ml) is added and the mixture is washed well with H20. The dried (Na2S04) organic phase is evaporated to yield the dihaloalkane. 

The p-bromo (or chloro) alcohol (50 ml) in PhH (330 ml) is refluxed with aqueous NaOH (29%, 17 ml) and TEBA-CI (3.3 g, 18 mmol) for 0.5-1 h. The cooled organic phase is separated, washed well with H20, dried (Na2S04), and evaporated to yield the oxirane, which can be purified by chromatography. 

The appropriate alkyl 2-bromomethylpropenoate (l mol) TEBA-Cl (2.3 g, 10 mmol), and /-BuO,H (90%, 110 g, l.l mol) in CH2Cl2 (150 ml) are stirred at -10°C. Powdered KOH (56 mg, l. I mol) is added portionwise such that the reaction temperature does not exceed -5°C. On complete addition of the hydroxide, the mixture is stirred at -5°C for 30 min and then allowed to come to room temperature and stirred for a further I h. The mixture is filtered and evaporated under reduced pressure. n-C,H12 (200 mi) is added to the residue and the organic solution is filtered, washed with H20 (100 ml), dried (MgS04), and evaporated to yield the peroxide (ethyl ester, 92% menthyl ester, 85% /-butyl ester, 45%). 

Method A The glucopyranosyl bromide (1 mmol) in CH2C12 (10 ml) and HzO (10 ml) is added to the phenol (3 mmol) and TEBA-C1 or Adogen (0.2 mmol) in aqueous KOH or NaOH (25 mmol) and the mixture is stirred at room temperature for 8-60 h. The organic phase is separated, washed with H20, dried (MgS04), and evaporated to yield the O-aryl derivative (68% from phenol 60% from 2-cresol 53% from 3-chlorophenoI, 54% from 4-methoxyphenol 56% from 4-nitrophenol 57% from 1-naphthol 44% from thio-phenol 36% from 8-hydroxyquinoline). 

Method E (t-butyl esters of peptides and amino acids) K2CO, (36 g) is added to the amino acid (10 mmol) and TEBA-C1 (2.28 g, 10 mmol) in MeCONMe2 (75 ml) at room temperature. Me,CBr (65.75 g, 0.48 mol) is then added and the mixture is stirred at 55 °C for 24 h. H20 (1000 ml) is added to the cooled mixture and the precipitated material is collected and extracted with EtOAc (250 ml). The extract is washed with H20 (2 x 100 ml), dried (Na2S04), and evaporated to yield the /-butyl ester (80-100%) Method F (from ethylene carbonates) Ethylene carbonate (2 g, 22 mmol), the carboxylic... 

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