Methylation, aromatics

Oxidation of monophenols to polyphenols or oxidation of aromatic methyl groups by persulfates (Caro s acxJ)... 

Acid catalyzed cleavage of aromatic methyl or ethyl ethers Quantitative methoxy group determination Also ether cleavage with tnmethylsilyl Iodide ... 

Birch s procedure for tropone synthesis appears to be widely applicable to 2,3- or 2,5-dihydroanisole derivatives which are readily obtained by reduction of appropriate aromatic methyl ethers by alcoholic metal-ammonia solutions. " Additional functional groups reactive to dibromocarbene or sensitive to base such as double bonds, ketones and esters would need to be protected or introduced subsequent to the expansion steps. 

Dimethyl carbonate, (Bu2N)2C=NMe, 180°, 4.5 h, 54-99% yield. In the presence of this guanidine, aromatic methyl carbonates are converted to methyl ethers with loss of CO2. 

Replacement of one of the aromatic methyl groups in lido- M/ne by a carboxylic ester proves consistent with pharmacologic lu-Livity. The product, tolycaine (76) is obtained from the iiiithranilic ester, 75, by the same two-step scheme as the proto-Iypc drug. 

The product has the following spectral properties infrared (KBr) cm.-1 3103 and 3006 (aromatic C—H), 2955, 2925, and 2830 (aliphatic C—H stretching), 1257 and 1032 (aromatic methyl ether), 841 and 812 (C—H out-of-plane bending of isoxazole C4—H and 4-substituted phenyl) proton magnetic resonance (trifluoroaeetic acid) 5, multiplicity, number of protons, assignment 3.98 (singlet,... 

The reaction of methyl ketones with a calculated amount of BTMA Br3 in aq. sodium hydroxide at room temperature and subsequent acid hydrolysis gave carboxylic acids together with bromoform in good yields. Aliphatic and aromatic methyl ketones have usually been reacted (Fig. 30) (ref. 38). 

Condensation of aromatic methylesters such as methyl 4-methoxybenzoate 351 a or methyl 4-hydroxybenzoate 351b with excess sodium-HMDS 486 in a mixture of THF-l,3-dimethyl-imidazolin-2-one (DMEU) at 185 °C in a closed vessel affords 59 or 93% of 4-hydroxybenzonitrile 298 as well as 26% 352 with smooth cleavage of the aromatic methyl ether in 351a (Scheme 4.47). Methyl indole-3-carboxylate gives hkewise 3-cyanoindole in 81% yield [127] (cf. also ref [92] in section 4.3). 

Scheme 12.22 provides some examples of the oxidation of aromatic alkyl substituents to carboxylic acid groups. Entries 1 to 3 are typical oxidations of aromatic methyl groups to carboxylic acids. Entries 4 and 5 bring the carbon adjacent to the aromatic ring to the carbonyl oxidation level. 

These results indicate that the aliphatic portion of the coal is very important in the initial phases of coal conversion. Weak linkages must be associated with the aliphatics in coal though they have not as yet been completely identified. Both of the above methods show an increase in the aromatic methyl content of SRCs at short times which indicates that cleavage at a benzylic carbon is important in dissolving the coal. 

The activity of PK and NRPSs is often precluded and/or followed by actions upon the natural products by modifying enzymes. There exists a first level of diversity in which the monomers for respective synthases must be created. For instance, in the case of many NRPs, noncanonical amino acids must be biosynthesized by a series of enzymes found within the biosynthetic gene cluster in order for the peptides to be available for elongation by the NRPS. A second level of molecular diversity comes into play via post-synthase modification. Examples of these activities include macrocyclization, heterocyclization, aromatization, methylation, oxidation, reduction, halogenation, and glycosylation. Finally, a third level of diversity can occur in which molecules from disparate secondary metabolic pathways may interact, such as the modification of a natural product by an isoprenoid oligomer. Here, we will cover only a small subsection of... 

Pelah, Z. Wilson, J.M. Ohashi, M. Bud-zikiewicz, H. Djerassi, C. Mass Spectrometry in Structural and Stereochemical Problems. XXXIV. Aromatic Methyl and Ethyl Ethers. Tetrahedron 1963, 19, 2233-2240. 

The oxadiazoles 77 were also obtained by anodic intramolecular cyclization of 1-arylmethylenesemicarbazides 76 in CH3OH-O.I mol/1 Et4C104 solution in 51-65% yield [55]. The aromatic methyl esters were also formed either as a minor or major product in 55-80% yield (Scheme 38). The selectivity of the... 

S-Oxidation to sulfoxide and sulfone aromatic methyl group hydroxylation... 

Aromatic methyl group hydroxylation and oxidation to aldehyde and carboxylic acid Aspergillus sclerotiorum, Aspergillus sp.)... 

Compound (B), being an oxidation product of a ketone should be a carboxylic acid. The molecular formula of (B) Indicates that it should be benzoic acid and compound (A) should, therefore, be a monosubstituted aromatic methyl ketone. The molecular formula of (A) indicates that it should be phenyl methyl ketone (acetophenone). Reactions are as follows ... 

In recent work a serendipitous discovery showed that strongly acidic chloroaluminate-containing ionic liquids, whether in combination with trialkylam-monium or with dialkylimidzolium cations, are active and selective for the cleavage of aromatic methyl ethers, even at temperatures <40°C. The ionic liquids are consistently better catalyst than AICI3 for this type of reaction 139). 

The isolation of carbazole (1), 3-methylcarbazole (2), and several oxidized derivatives of 3-methylcarbazole from taxonomically related higher plants of the genera Glycosmis, Glausena, and Murraya (family Rutaceae) indicates that the aromatic methyl group of the biogenetic key intermediate 3-methylcarbazole can be eliminated oxidatively (5,6). Most of the carbazole alkaloids isolated from the... 

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