Hydroquinone trimethyl

SYNS 1,4 -BENZENEDIOL, 2,3,5-TRIMETHYL- (9CI) V-CUMOHYDROQUINONE HYDROQUINONE, TRIMETHYL- TRIMETHYLHYDROQUINONE 2,3,5-TRIMETHYLHYDROQUINONE... 

Preparation by reaction of veratroyl chloride (3,4-dimethoxybenzoyl chloride) with hydroxy-hydroquinone trimethyl ether (1,2,4-trimethoxybenzene) in the presence of aluminium chloride,... 

Toluhydroquinone and methyl / fX butyUiydroquinone provide improved resin color retention 2,5-di-/-butyIhydroquinone also moderates the cure rate of the resin. Quaternary ammonium compounds, such as benzyl trimethyl ammonium hydroxide, are effective stabilizers in combination with hydroquinones and also produce beneficial improvements in color when promoted with cobalt octoate. Copper naphthenate is an active stabilizer at levels of 10 ppm at higher levels (150 ppm) it infiuences the cure rate. Tertiary butylcatechol (TBC) is a popular stabilizer used by fabricators to adjust room temperature gelation characteristics. 

Trimethyl-l,4-hydroquinone (2,3,5-trimethylbenzene-l,4-diol) [700-13-0] M 152.2, m 173-174°, pKEst(i) 11-1 pKesi(2) 12-7. Recrystd from water, under anaerobic conditions. 

The strong Bronstedt acid nature of some hexacoordinated phosphorus derivatives, [7",H ] (Et20)4 in particular, was recently used within the context of an industrial application [36]. The conjugated acid of tris(oxalato)phosphate anion 7 was found to effectively catalyze the ring-forming reaction of trimethyl-hydroquinone 63 with isophytol 64 to give (all rac)-a-tocopherol 65 (ethylene-carbonate/heptane 1 1,100 °C, 90%, Scheme 19). This process is particularly... 

Similarly, 2,3,5-trimethyl-1,4-hydroquinone (TMHQ), a key intermediate in the synthesis of vitamin E, is produced via oxidation of 2,3,6-trimethylphenol to the corresponding benzoquinone. Originally this was performed by reaction with chlorine followed by hydrolysis, but this process has now been superseded by oxidation with O2 in the presence of a Cu2Cl2/LiCl catalyst (see Fig. 2.20) (Mercier and Chabardes, 1994). Alternatively, this oxidation can also be cataly.sed by a heteropolyanion (Kozhevnikov, 1995). 

Apart from examples given by Chakrabarti and Sharma (1993) and Sharma (1995), a number of additional examples can be cited. A reference will be made to the reaction of ketoi.sophorone with AC2O to give trimethyl hydroquinone diacetate where a cationic ion-exchange resin (CIER) works in an elegant and functional way (Eqn. (7)). 

The oxidation behavior of 3-oxa-chromanols was mainly studied by means of the 2,4-dimethyl-substituted compound 2,4,5,7,8-pentamethylM /-benzo[ 1,3]dioxin-6-ol (59) applied as mixture of isomers 27a it showed an extreme dependence on the amount of coreacting water present. In aqueous media, 59 was oxidized by one oxidation equivalent to 2,5-dihydroxy-3,4,6-trimethyl-acetophenone (61) via 2-(l-hydroxyethyl)-3,5,6-trimethylbenzo-l,4-quinone (60) that could be isolated at low temperatures (Fig. 6.41). This detour explained why the seemingly quite inert benzyl ether position was oxidized while the labile hydroquinone structure remained intact. Two oxidation equivalents gave directly the corresponding para-quinone 62. Upon oxidation, C-2 of the 3-oxa-chroman system carrying the methyl substituent was always lost in the form of acetaldehyde. 

Trimethyl phenol 1-Naphthol p-Phenylphenol p-Methoxyphenol Hydroquinone... 

All three types of reactions can also be used for the production of substituted quinones and hydroquinones. For example, BASF has developed two laboratory processes for the synthesis of trimethyl-p-benzoquinone and trimethylhydroquinone. The latter is required for the synthesis of vitamin E. 

In practice, a-tocopherol (rac-1) is industrially produced on a large scale by an acid-catalyzed reaction of trimethyl hydroquinone (3) with all-rac-isophytol (4) as a mixture of all eight possible stereoisomers." ... 

This acid-catalyzed condensation of trimethyl hydroquinone (14) is performed in methanol. 

The synthesis of chroman 15 involves an acid-catalyzed condensation of trimethyl hydroquinone (14) with methyl vinyl ketone (9), but unfortunately the mechanism is not clarified in detail and the role of the ortho formate is also not clear. Scott et al. assumed that the reaction proceeds via the intermediates 27 and 28. ... 

Adducts with quinoitcs, a-diketones, and ot-keto esters. Ramirez and co-workers found that chloranil and other 1,4-benzoquinones react readily with trimethyl phosphite to form the methyl ethers of the hydroquinone monophosphates, for example (3), and presented evidence that the primary product is the dipolar ion (2). 

Phytol, CAS no. [150-86-7] C20H40O, an alcohol obtained by the decomposition of chlorophyll is an odorless liquid, BP 202—204°C/10mm Hg and has been used in the synthesis of vitamin E. On reaction with trimethyl hydroquinone phytol is converted to a-tocopherol, etc. 

Vitamin E obtained from natural products is, however, much costlier than the one synthesized from 2,3,6-trimethyl phenol, via 2,3,6-trimethyl hydroquinone and phytol. 

A similar ring structure resulted, with no evidence of live-membered ring formation, from the treatment of methyl vinyl ketone cyanohydrin and phosphoric acid in toluene/nitromethane during 1 hour with a suspension of 2,3,6-trimethyl hydroquinone and boron trifluoride in toluene at 0-5°C, followed by reaction at ambient temperature for 13 hours to give an 81% yield of 2-cyano-2,5,7,8-tetramethyl-6-hydroxychroman (ref. 163). 

The highly substituted hydroquinone monoacetate shown with 3-chloro-2-methyl -1-propene in dichloromethane/acetic acid (10 1) containing zinc chloride after reaction with stirring during 6 hours at ambient temperature gave 2,2,7-trimethyl-... 

The nickel(IV) oxime, bis(6-amino-3-methyl-4-azahexa-3-ene-2-one oxime)nickel(IV), and the nickel(III) oxime, (15-amino-3-methyl-4,7,10,13-tetraazapentadeca-3-ene-2-one oxime)nickel(III), complexes react with hydro-quinone. Proton-related equilibria for both the nickel complexes and the hydroquinone could be elucidated from the kinetic details. For reactions with the complexes and the hydroquinone could be elucidated from the kinetic details. For reactions with the Ni(III) complex there is evidence of an inner-sphere process. The [NiL(TCCat)] complex (TCCatH2 = tetrachlorocatechol L = 2,4,4-trimethyl-1,5,9-triazacyclododec-l-ene) forms a 1 1 adduct with tetrachloro-1,2-benzoquinone. Spectroscopic evidence suggests that this compound can be described formally as a quinone adduct of a Ni(I)-semiquinone moiety arising from inner-sphere ligand oxidation. The crystallographically determined structure (11) is shown below. Several copper complexes of a vareity of semiquinones also exist in solution in equilibrium with the corresponding catechol complexes. ... 

Professor Karror, who is fortunately with us and whoso outstanding role will bo properly emphasized by the first speaker at this Symposium, was the first to synthesize a-tocophcrol by eondensing phytyl bromide with trimethyl hydroquinone. He worked out the means of estimating the toeopherols based on the fact that the free compounds readily reduce gold chloride, whereas the acetates do not. His later work included a magnificent study of the relationships of the vitamin activity wnth variations in the molecular structure (Karrer et al., 1938). 

Todd independently isolated /3-tocopherol from w hcat germ oil, showed that on pyrolysis it yielded trimethyl hydroquinone, and independently synthesized a-tocopherol by condensing phytol with trimethyl hydroquinone he synthesized the three dimethyl toeopherols by condensing phytol with the three dimethyl hydroquinones (Bcrgel et al., 19.38). He also synthesized some cjhromans and coumarans by unambiguous methods and showed that they closely resembled the natural tocopherol. 

Trimethyl-1,4-naphthoquinone (TMNQ) is a quinone that was recently isolated from tobacco leaves and was shown to slow the metabolism of dopamine, a neurotransmitter whose depletion can lead to Parkinsons disease. What is the structure of the hydroquinone whose oxidation gives TMNQ ... 

Monostearyl trimethyl ammonium chloride. See Steartrlmonlum chloride Monosteol. See Propylene glycol stearate Mono-tertiarybutylhydroquinone. Seet-Butyl hydroquinone Monotetradecylamine. See Myristamlne Monothloglycerol a-Monothloglycerol. See Thioglycerin Monothiuram. See Tetramethylthiuram monosulfide Monotridecyl phosphate. See Tridecyl phosphate Montan acid wax... 

Ochi, M., Kotsuki, H., Inoue, S., Taniguchi, M., and Tokoroyama, T. (1979a) Isolation of 2-(3,7,ll-trimethyl-2,6,10-dodecatrienyl)-hydroquinone from the brown seaweed Dictyopteris undulata. Chem. Lett., 831-832. 

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