2.5.6- Trimethyl-3-methoxyphenol

Figure 1. Formulas of major retinoids and of P-carotene. A, all-tranj retinol B, all-tranj retinal C, all-rran retinoic acid D, 11-cw retinal E, 13-cw retinoic acid F, all-tran retinyl palmtate G, ai -trans retinoyl p-glu-curonide H, the trimethyl methoxyphenol analog of all-rra 5 retinoic acid (etretin, acitretin) I, all-rra 5 p-carotene. From [5], p. 110, reprinted with the permission of the International Life Sciences Institute, Washington DC 20036-4810, Copyright 1996.

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

Potassium hydroxide, 258 Trimethylsilyl chlorochromate, 327 of carbon-carbon double bonds substituted by heteroatoms m-Chloroperbenzoic acid, 76 of oximes to carbonyl compounds Lithium aluminum hydride-Hexa-methylphosphoric triamide, 159 Titanium(III) chloride-Diisobutylalu-minum hydride, 303 Trimethylsilyl chlorochromate, 327 of protected alcohols Chlorodimethylthexylsilane, 74 Formic acid, 137 p-Methoxyphenol, 181 of thioacetals and -ketals Methoxy(phenylthio)trimethyl-silylmethane, 182... 

A unique feature of this procedure is the selective monode-methylation of the dimethyl ether. The scope of this reaction is illustrated6 in part by the preparation in high yield of p-methoxyphenol, guaiacol, and phloroglucinol dimethyl ether from the respective fully O-methylated compounds. An exception is pyrogallol trimethyl ether which affords pyrogallol 1-monomethyl ether in high yield.6... 

Reactions of (1) and (2) with phenols give o-methylthiomethylated phenols (eq 2). Mixtures of the phenols and 0.5 equiv of (1) or (2) are heated without solvent at 120-130 °C for 3-7 h. 2-Methylthiomethylphenols are obtained from 2- and 4-methyl, 2,5- and 3,5-dimethyl-, 2,3,5-trimethyl-, and 2-methoxyphenols in 55-95% yield (Table 2). In some case, significant amounts of bis(methylthiomethyl) products are also formed. The yields using (2) are higher than those using (1). 

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