Phenol ethers hydroxylation

Styrene C6H5CH=CH2. Alkali Peroxy compds Vap in Air 1.1 to 6.1% > Ambient > Ambient Inhibitor—Methyl Ether of Hydroquinone—10-15 ppm, Phenol Subst-Hydroxyl Amine, etc. Store below 70°F. Avoid sparks in. vap/air mixt 17.4-17.8 490 Soln polymerization catalyzed with w or Ti tetrachloride. Also self polymerization... 

The reaction was also found to be inhibited by addition of dioxan and tetra-hydropyran, the rate decrease being proportional to the ether concentration. The results were rationalised by the assumption that 2 1 and 1 1 phenol ether complexes were formed, respectively. The inhibition was attributed to participation of the hydroxyl group in solvation of the halogen atom of the alkyl halide, though this seems much less likely than a straightforward modification of the electron-supplying effect of the substituent3 54. 

Hydroxylation of phenol or phenol ethers with H2O2 on a so called titanozeosilite, has also been reported and is very similar to the TS-1 catalyzed reaction [115]. The essential difference between TS-1 and... 

Condensation takes place in the p-position to the hydroxyl group. Di-and poly-hydric phenols and phenolic ethers can also be employed, as can hydroxy and methoxy nitriles (J. C. S., 118, 309). 

A typical lignin C6C3 unit see reaction scheme below) contains a side chain at position 1, a methoxyl at position 3, and a phenolic hydroxyl or phenol ether group at position 4. Another methoxyl group or a condensed... 

When halogenated phenols or phenolic ethers are nitrated with nitric acid a halogen o- or p- to hydroxyl or alkoxyl group can also be replaced. The ease of replacement appears to be in the order Cl< Br[Pg.128]

The phenolic hydroxyl, resulting from the hydrolysis of the phenol ether, affects the distribution of electrons in the benzene ring. Back-donation of electrons from the phenolic oxygen facilitates elimination of ben-zylic fluorine next to the benzene ring. 

Hydroxylation of phenol and phenol ethers Al-B High selectivity to p-C6Hi(OH)2 56... 

Oxidative cleavage of aUyl and propargyl ethers. Hydroxyl and phenolic groups have been protected as the allyl ethers. Hydrolytic cleavage of protective group involved isomerization to the propenyl ether by potassium r-butoxide in DMSO followed by hydrolysis (1, 300 2, 158). Japanese chemists4 now find that allyl ethers can be cleaved in one step by oxidation with a slight excess of selenium dioxide in acetic acid-dioxane (reflux, 1 hr.). Presumably a hemiacetal of acrolein... 

Removal of non-basic impurities. In the work-up of a crude mixture of water-insoluble alkaloids, isolation procedures are often impeded by the presence of persistent non-basic impurities that are difficult to remove by conventional means, including column chromatography phenols and hydroxylated terpenoid constituents are particularly troublesome in this regard. In many instances, removal can be achieved by prolonged ether extraction of a dilute sulphuric acid solution of the crude bases in a continuous extraction apparatus [128]. In one case this also failed, but a counter-current method referred to later removed the impurity. 

LjPt(CF3)X complexes (with L = tetraaryldiphosphines and X = CH CIj, OH, OPh) are hydroxylation catalysts of phenol and phenol ethers, with 70% HjO [46]. In all cases, high ortho-selectivity (up to 95%) is observed. Phenylalanine is hydroxylated by a water-soluble iron porphyrin complex to tyrosine and dihydroxy phenylalanine (DOPA) in good yields [47]. Other hydroxylation catalysts of various aromatic substrates are halogenated porphyrin complexes of Fe and Mn [48-49],... 

Constantini. M., Jean-Pierre, L., Gubcimann, M. and Popa Jean. M, (1987). Process for the hydroxylation of phenols and phenol ethers. Eur. Patent, 346,250 (to Enichem Synthesis). 

Johnstone, R.A.W. (1997). Selective hydroxylation of phenol or phenolic ethers. US Patent. 5,675,042 (to Solvay Intcrox Limited). 

Other phenols and phenol ethers were examined to assess the breadth of activity of this catalyst. Anisole was selected as an electron rich aromatic system though less so than phenol. A cleaner reaction at lower conversion was expected. Under similar conditions employed for phenol hydroxylation, a 20% conversion of anisole was measured with selectivity to 4-methoxy phenol of 15% and to guiacol of 42%. 1-naphthol was also assessed. No conversion was seen, presumably due to the bulky nature of the molecule. These findings are consistent with a mechanism involving an electrophilic oxidant species. 

Isopropyl 2-iodoxybenzoate is a useful reagent for the clean, selective oxidation of organic sulfides to sulfoxides [1127]. This reaction proceeds without overoxidation to sulfones and is compatible with the presence of the hydroxy group, double bond, phenol ether, benzylic carbon and various substituted phenyl rings in the molecule of organic sulfide. Duschek and Kirsch have reported that isopropyl 2-iodoxybenzoate in the presence of trifiuoroacetic anhydride can be used for the a-hydroxylation of p-keto esters at room temperature in THF [1128]. 

A series of patents issued to Asahi Chemical Industry Co., deal with the modification of hexamethylenediamine by reaction with (meth)acrylic-, glycidyl ether-, hydroxyl-, amino-, amido-, or carboxy-substituted vinyl compounds, isocyanate, and amino acid compounds (Table IV). These modified amine curing agents are active at low temperatures and, in some cases, on wet substrates. Amine-substituted resole phenolics have also been described as useful epoxy curing agents." " Preparation of these curing agents is via condensation of the phenol, formaldehyde, and polyamine (Eq. 8). 

Phenol, anisole, and phenolic ethers are readily hydroxylated by hydrogen peroxide in the presence of microcrystalline ZrP and acetic acid (151). The selectivity for catechol formation was greater than 29% at 47% conversion, and hydroqui-... 

The Mitsunobu reaction has been extensively used for the formation of aziridines. Recently, Cossy et al. were interested in inverting the benzylic hydroxyl group in 167 to prepare a precursor of (phenol derivative 169. Increasing the concentration of 2-ethoxyphenol to 20 equiv led to the formation of the desired phenol ether in good yield. The Mitsunobu reaction has also been used for the preparation of amino acid derived aziridines these compounds can then be used for the synthesis of pseudopeptides. 

In an alcohol, a hydroxyl (—OH) group is bonded to the hydrocarbon chain of an alkane. In a phenol, the hydroxyl group is attached to a benzene ring. Molecules of alcohols and phenols have a bent shape around the oxygen atom. In an ether, an oxygen atom is attached to two carbon atoms (see Figure 17.4). 

Phenol, phenolic ethers H2O2 Hydroxylation Microcrystalline ZrP 172... 

The preparation of industrially important alkyl atyl ethers was reported by Saidi and Rajabi (2003). A number of phenolic compounds such as naphthols, phenols, and hydroxyl coumarins were 0-methylated with trimethyl phosphite or trimethyl phosphate under microwave irradiation and solvent-free condition in almost quantitative yields. Reaction of 2-naphthol with trimethyl phosphate gave mixture of... 

Aryl ethers are best prepared by the Williamson method (Section 16 6) Alkylation of the hydroxyl oxygen of a phenol takes place readily when a phenoxide anion reacts with an alkyl halide... 

---