2.6- Di-tert-butylphenol

Di-tert-butylphenol (2,4-DTBP) or 2,4-bis(l,l-dimethylethyl)phenol is produced by the alkylation of phenol with isobutylene under acid catalysis using a mole ratio of 2 1 (isobutylene to phenol). The cmde product contains 4-/ f2 -butylphenol, 2,4-di-/ f2 -butylphenol, and 2,4,6-tri-/ f2 -butylphenoL The... 

Kodera and co-workers demonstrated348 that complex (400) (distorted TBP Cu-Cu 2.926 A 2/=—148 cm-1 they also characterized a closely similar ethoxy-bridged complex with two molecules of MeCN) catalyzes the quantitative oxidation of 2,4-di-tert-butylphenol to 3,3, 5,5 -tetra-tert-butyl-2,2 -dihydroxybiphenyl with H202. Krebs and co-workers provided models for the... 

Di-tert-butyl-p-cresol, 3 105 2,4-Di-tert-butylphenol (2,4-DTBP),... 

Di-tert-butylphenol Phenol, 2,4-di-tert-butyl- (8) Phenol, 2,4-bis(1,1-dimethylethyl)- (9) (96-76-4)... 

Figure 4. Spectral sensitivity data of PMMA and sensitized PMMA obtained by the equipment shown in Figure 3 (A) PMMA (B) PMMA -f- p-teit-butyl benzoic acid (C) PMMA + 2,4-di-tert-butylphenol (D) PMMA + 2,4,6-tri-teit-butyl-...

Figure 9. Spectral sensitivities of PMMA and sensitized PMMA ( ) PMMA (tH) PMMA + p-tert-bvtyl benzoic acid (A) PMMA -)- 2,4-di-tert-butylphenol (Q) PMMA -)- 2,4,6-tri-tert-butylphenol...

Stack and co-workers recently reported a related jx-rf / -peroxodi-copper(II) complex 28 with a bulky bidentate amine ligand capable of hydroxylating phenolates at - 80 °C. At - 120 °C, a bis(yu,-oxo)dicopper(III) phenolate complex 29 with a fully cleaved 0-0 bond was spectroscopically detected (Scheme 13) [190]. These observations imply an alternative mechanism for the catalytic hydroxylation of phenols, as carried out by the tyrosinase metalloenzyme, in which 0-0 bond scission precedes C - 0 bond formation. Hence, the hydroxylation of 2,4-di-tert-butylphenolate would proceed via an electrophilic aromatic substitution reaction. 

Table 2. Polymerization of methyl methacrylate (MMA) via an enolatealuminum porphyrin (2, R=Me) in the presence of methylaluminum his(2,4-di-tert-butylphenolate) (3b) ...

A novel mesoporous intercalate belonging to the class of mesostructured solid acids known as porous clay heterostructures (PCH) has been synthesized through the surfactant - directed assembly of silica in the two - dimensional galleries of saponite. The new saponite PCH, denoted SAP-PCH, exhibits a basal spacing of 32.9 A, a BET surface area of 850 m2/g and pore volume of 0.46 cm3/g. SAP-PCH is an effective catalyst for the condensed phase Friedel-Crafts alkylation of bulky 2,4-di-tert-butylphenol (DBP) with cinnamyl alcohol to produce a large flavan, namely, 6,8-di-tert-butyl-2,3-dihydro[4H]benzopyran. 

Here we report the synthesis and catalytic application of a new porous clay heterostructure material derived from synthetic saponite as the layered host. Saponite is a tetrahedrally charged smectite clay wherein the aluminum substitutes for silicon in the tetrahedral sheet of the 2 1 layer lattice structure. In alumina - pillared form saponite is an effective solid acid catalyst [8-10], but its catalytic utility is limited in part by a pore structure in the micropore domain. The PCH form of saponite should be much more accessible for large molecule catalysis. Accordingly, Friedel-Crafts alkylation of bulky 2, 4-di-tert-butylphenol (DBP) (molecular size (A) 9.5x6.1x4.4) with cinnamyl alcohol to produce 6,8-di-tert-butyl-2, 3-dihydro[4H] benzopyran (molecular size (A) 13.5x7.9x 4.9) was used as a probe reaction for SAP-PCH. This large substrate reaction also was selected in part because only mesoporous molecular sieves are known to provide the accessible acid sites for catalysis [11]. Conventional zeolites and pillared clays are poor catalysts for this reaction because the reagents cannot readily access the small micropores. 

The alkylation of 2,4-di-tert-butylphenol with cinnamyl alcohol was carried out in a 25 ml flask with 0.25 mmol 2,4-di-tert-butylphenol (Aldrich) and 0.25 mmol cinnamyl alcohol (Aldrich) using 12.5 ml isooctane as solvent. When the solution was heated and maintained at 60°C, 125 mg catalyst was added. After 6 h s reaction, the catalyst was filtered and extracted with dichloromethane to recover adsorbed reaction products. 1,3 -Di-tert-butylbenzene was used as internal standard and the products were analyzed by GC (HP5890) and GC-MS (HP5890). 

Reaction condition 125 mg catalyst, 0.25 mmol 2,4-di-tert-butylphenol, 0.25 mmol cinnamyl alcohol, 12.5 ml isooctane, 60°C, 6 h. 

In this case, not only was 2,4-di-tert-butylphenol more active than 2-tert-butyl-4-methylphenol, but contrary to the 2,4,6-trisubstituted model compounds, a greater efficiency was achieved after exchanging the methyl... 

Table 3. The catalytic activity of Al-substituted (2 mol %) MSU-G and MCM-41 materials for the alkylation of 2,4-di-tert-butylphenol (DTBP) with cinnamyl alcohol."...

MontmoriUonite-KSF catalyzes the transalkylation of 2,4-di-tert-butylphenols in the presence of excess phenol or tolnene. The ortho-tert-hvAy group is preferentially transferred in the process, giving the para-fert-butylphenol as the major product (equations 14 and 15). Using xylenes as the solvent at higher temperatures (140 °C) it was possible to transalkylate both of the fert-butyl groups. The catalyst can be recycled without loss of reactivity or selectivity . 

Highly acidic Al-MCM-41, U-MCM-41 and Th-MCM-41 catalysts have been used for the Friedel-Crafts alkylation of 2,4-di-tert-butylphenol with cinnamyl alcohol to give the corresponding substimted benzopyran (equation 21) °. The reaction involves an initial ort/io-alkylation, followed by an acid-catalyzed intramolecular cyclization. Loss of the 2-terf-butyl group results in minor byproducts. 

DTBP (2,4-di-tert-butylphenol) in ionic liquids. Moreover, the selectivity to 2,4-DTBP was increased from 29.7% to 64.9%. For the HPW/MCM-41-catalyzed alkylation reactions, the improvement in effects of ionic liquids was also observed. 

---