Coupling Cresol

Coupling tetra2o (7) with o-cresol has been reported to give a dye (19) which is less alkah-sensitive than Direct Yellow 4 (Cl 24890) and to have better cold-water solubiUty than Direct Yellow 12 (Cl 24895) (18). One reference is made to a stilbene laser dye (10) and two each to dyes for 1ight-po1ari2ing films (34,35) and reprographic inks (36,37). 

The early yellow disperse dyes were based on phenolic coupling components, eg, Cl Disperse Yellow 3 (92) (diazotized 4-arninoacetanihde coupled to -cresol) which is still used today for the coloration of cellulose acetate and nylon fibers. 

An azo coupling reaction of monatomic phenols with diazotized 4-nitroaniline has been investigated. By HPLC, NMR, elemental analysis, UV and IR spectroscopy it has been shown that the azo derivatives of o-guaiacol, o- and m-cresols interact with an excess of diazonium in pH interval of 4,5-9,5 and form corresponding 4,4-di(4-nitrophenylazo)-2,5-cyclohexadien-1 -ones. 

Oxidation of /U-cresol afforded a triphenol 22 which is approximately half the molecule. The central hydroxyl of the triphenol could be selectively methylated and then the compound was ort/ro-brominated and bridged using 1,3-dibromopropane to give 23. Metallation with butyllithium followed by iron catalyzed coupling afforded the macrocycle as indicated. 

A method suitable for quantification of the functional class of bis(ethanol)amine antistatics, which lack UV chromophores, consists of reaction with methyl orange [53]. Atmer 163 (alkyl-diethanol amine) has been determined as a yellow complex at 415 nm after interaction with a bromophenol/cresole mixture [64]. Hilton [65] coupled extracted phenolic antioxidants with diazotised p-nitroaniline in strongly acidic medium and carried out identification on the basis of the visible absorption spectrum in alkaline solution. The antioxidant Nonox Cl in... 

With an effective strategy for construction of the diazofluorene established, we set out to prepare the coupling partners required for synthesis of (—)-kinamycin F (6). The synthesis of the enone 117 began with meta-cresol (128, Scheme 3.23). Silylation formed the silyl ether 119 in nearly quantitative yield. Birch reduction of the silyl ether 119 formed the cyclohexadiene derivative 129 in excellent yield. Asymmetric dihydroxylation [52] of 129 occurred regioselectively to afford the... 

Coupling, reductive, of o-chlorobenzal-dehyde by hexamethylphosphor-ous triamide to give 2,2 -di-chloro-a,a -epoxybibenzyl, 46, 31, -Cresol, 48, 96 -t-Crotonolactone, 46,22 Crotyl diazoacetate, 49, 22, 24 Cupric acetate in coupling of phenyl-acetylene, 46, 39... 

Scheme 11.5. Synthesis of 7-mer-neo-conjugate N-Neo-C. (i) Deprotection with 4% trichloroacetic acid in CH2CI2, and coupling with 3 in the presence of 1/7-tetrazole followed by capping with acetic anhydride in pyridine/THF solution, and oxidation with I2 in THF/H20/pyridine solution (ii) p-elimination followed by deprotection from the solid support using cone. NH4OH (c) 1,4-dioxane solution containing 3% CF3CO2H and 1% m-cresol (v/v/v %). Reprinted with permission from Bioconj. Chem. 2007, 18, 160-169.

Timari et al. described a total synthesis of furostifoline (224) starting from commercial o-cresol (1133). The key steps in this approach are the Suzuki coupling to the o-nitrobiaryl 1139 and subsequent Cadogan s reductive cyclization via a nitrene intermediate (692). 

With aromatic compounds conditions can be found so that ring oxidation predominates and phenolic compounds are formed. Benzene is oxidized quantitatively to phenol. Toluene is oxidized to o-cresol, m-xy-lene to l,3-xylen-4-ol, and naphthalene to f-naphthol. The addition of certain additional catalyst, such as molybdenum oxide, promoted coupling reactions and biphenyl was formed from benzene, bi- or poly-tolyl hydrocarbons from toluene, di- and polyxylyls from wi-xylene, and a... 

The amount of cresol in the concentrated extract can then be determined by high performance liquid chromatography (HPLC) (DeRosa et al. 1987 Yoshikawa et al. 1986) or gas chromatography (GC) coupled to either a flame ionization detector (FID) or a mass spectrometer detection system (Angerer 1985 Needham et al. 1984). Separation of the cresol isomers by gas chromatography is readily accomplished, and the use of an appropriate internal standard allows the determination of their concentrations. Although exact detection limits were not given for the above GC methods, a concentration of 10 ppm appears to be readily determined. 

The solution must be strongly acid in order to avoid the coupling reaction between the undecomposed diazonium salt and the phenol (seeunder Azo Dyes). For the preparation of phenol and the cresols, the aqueous solution of the diazonium compound is warmed to about 50° at higher temperatures the reaction may become unduly vigorous and lead to appreciable quantities of tarry compounds ... 

Couplers may be hydroxy or amine derivatives of aromatic compounds, such as benzene, naphthalene or anthracene. Phenol, naptbol, aniline, cresol. paraaminophenol and dimethylpuraphenylenediumine are examples. With these compounds coupling takes place with the hydrogen atom which is in the ortho or para position ut the hydroxy or amino group on the coupler. 

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