Oxidative Coupling Of Phenols Research Articles

High-performance liquid chromatography detection of morphine by fluorescence after post-column derivatisation: II. The effect of micelle formation

The phenolic oxidative coupling of morphine and related opiates to yield fluoescent products, used for post-column high-performance liquid chromatography detection, has been studied in micellar solutions. The nonionic surfactant, Triton X-100, was found to enhance the detection limit. This enhancement was a result of increased coupling rather than increased fluorescent response of the morphine dimer, pseudomorphine. Ionic surfactants either reduce the sensitivity of detection, or were not applicable to the reaction system used.

Ageing of SRC-II middle distillate from Illinois No. 6 coal: II. Further evidence of phenolic oxidative coupling in coal-derived liquids

Individual phenolic compounds in an SRC-II middle distillate were quantified before and after ageing in the presence of Cu and O 2. The concentration of each phenolic constituent decreased, indicating that they are consumed by a reaction that occurs during ageing. After ageing, a pentane-insoluble precipitate formed that was not present before ageing. Bulk characterization of this ageing product by low-voltage high-resolution mass spectrometry shows that it contains dimers, trimers, tetramers, etc., of phenols. These are the same kinds of products known to form during phenolic oxidative coupling reactions. This observation is taken as direct physical evidence that supports an earlier hypothesis that phenolic oxidative coupling reactions occur during ageing of SRC-II middle distillate in Cu O 2 environments.

Kinetics of oxidative coupling of phenols. Oxidation of pyrogallol by alkaline hexacyanoferrate(III)

The reaction of pyrogallol with alkaline hexacyanoferrate(III) at constant ionic strength gave 3,3′,5,5′-tetrahydroxy-4,4′-diphenoquinone in a yield of 80%. The rate is dependent on the first powers of the concentrations of substrate, oxidant and alkali. The reaction pathway could be visualized as proceeding via a radical intermediate formed in the rate determining step. This radical was detected by ESR spectroscopy as two triplets with the intensity ratios of (1,2,1), (1,2,1), and showed absorptions at 655 nm, and at 1560 cm−1 in the infrared region.

ChemInform Abstract: OXIDATIVE COUPLING OF PHENOLS. PART 8. A THEORETICAL STUDY OF THE COUPLING OF F PHENOXYL RADICALS

Chemischer InformationsdienstVolume 14, Issue 34 Physical Organic Chemistry ChemInform Abstract: OXIDATIVE COUPLING OF PHENOLS. PART 8. A THEORETICAL STUDY OF THE COUPLING OF F PHENOXYL RADICALS D. R. ARMSTRONG, D. R. ARMSTRONGSearch for more papers by this authorC. CAMERON, C. CAMERONSearch for more papers by this authorD. C. NONHEBEL, D. C. NONHEBELSearch for more papers by this authorP. G. PERKINS, P. G. PERKINSSearch for more papers by this author D. R. ARMSTRONG, D. R. ARMSTRONGSearch for more papers by this authorC. CAMERON, C. CAMERONSearch for more papers by this authorD. C. NONHEBEL, D. C. NONHEBELSearch for more papers by this authorP. G. PERKINS, P. G. PERKINSSearch for more papers by this author First published: August 23, 1983 https://doi.org/10.1002/chin.198334067AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume14, Issue34August 23, 1983 RelatedInformation

ChemInform Abstract: OXIDATIVE COUPLING OF PHENOLS. PART 7. SPIN‐DENSITY CALCULATIONS ON THE PHENOXY RADICAL

Chemischer InformationsdienstVolume 14, Issue 33 Physical Organic Chemistry ChemInform Abstract: OXIDATIVE COUPLING OF PHENOLS. PART 7. SPIN-DENSITY CALCULATIONS ON THE PHENOXY RADICAL D. R. ARMSTRONG, D. R. ARMSTRONGSearch for more papers by this authorC. CAMERON, C. CAMERONSearch for more papers by this authorD. C. NONHEBEL, D. C. NONHEBELSearch for more papers by this authorP. G. PERKINS, P. G. PERKINSSearch for more papers by this author D. R. ARMSTRONG, D. R. ARMSTRONGSearch for more papers by this authorC. CAMERON, C. CAMERONSearch for more papers by this authorD. C. NONHEBEL, D. C. NONHEBELSearch for more papers by this authorP. G. PERKINS, P. G. PERKINSSearch for more papers by this author First published: August 16, 1983 https://doi.org/10.1002/chin.198333067AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume14, Issue33August 16, 1983 RelatedInformation

Studies on the Synthesis of Morphine VI*

Experiments to find a biomimetic route for synthesizing morphine are summarized. Systematic investigations on the phenolic oxidative coupling have been revised and evaluated.

Phenolic oxidative coupling with hypervalent iodine. A synthesis of 6a-epipretazettine

Phenolic oxidative coupling with hypervalent iodine. A synthesis of 6a-epipretazettine

Kinetics of Oxidative Coupling of Phenols. Oxidation of Guaiacol by Alkaline Hexacyanoferrate(III)

Abstract The reaction between guaiacol and alkaline hexacyanoferrate(III), at constant ionic strength, gave a coupled product, 3:3′-dimethoxydiphenoquinone. The rate of the reaction was dependent on the first orders of the concentrations of substrate, oxidant, and alkali. The rate determining step involved the formation of a radical intermediate, which was detected by ESR spectroscopy.

Macromolecular imidazole copper complexes as catalysts for the oxidative coupling of phenols

In order to extend the investigation on soluble macromolecular imidazole derivatives as ligands for copper salts, two types of polymers were synthesized. Copolymerization of styrene and N-vinylimidazole yielded macromolecular ligands of type II in which the imidazole moiety is bound directly to the polyethylene backbone. Chloromethylation of polystyrene and amination with imidazole yielded macromolecular ligands of type III in which the imidazole moiety is bound via a benzyl group to the polyethylene backbone. Both polymers gave greenish-blue soluble copper complexes. These complexes are good catalysts for the oxidative coupling of 2,6-disubstituted phenols. They have been compared to their low molar mass analogue, N-methylimidazole (I). As substrate, 2,6-di-t-butylphenol and 2,6-dimethylphenol were chosen. Kinetic analysis were performed. The results for all three types of catalysts and for both substrates are discussed. The activities of the macromolecular catalysts were fairly high compared to other systems. Moreover the polymeric catalysts showed enhancement of re-oxidation rates compared to the low molar mass analogue ( I) due to the nonpolar field formed by the polymer ligand. Binding of ligands to macromolecules increases the steric hindrance towards substrate complexation at active sites. This can be decreased by binding the ligands via spacers to the macromolecule (as in III).

Kinetics of oxidative coupling of phenols: Oxidation of naphthols by alkaline hexacyanoferrate (III)

AbstractThe oxidation of naphthols by alkaline hexacyanoferrate(III), at constant ionic strength, gave coupled products. The rate of the reaction was dependent on the first powers of the concentrations of substrate, oxidant, and alkali. The activation energies were 31.8 and 34.5 kJ/mol for α naphthol and β naphthol, respectively. The reaction pathway was via the formation of a radical intermediate, which was detected by electron spin resonance spectroscopy.

Oxidative coupling of phenols. Part 10. The role of steric effects in the formation of C–O coupled products

The formation of C–O coupled products in the oxidative coupling of phenols is hindered by bulky ortho-substituents in the aryloxyl radical intermediates as shown by the predominant formation of the ortho-ortho-C–C coupling products in the oxidation of o-t-butyl- and 2,4-di-t-butyl-phenol. 3,5-Di-t-butyl-phenol gives exclusively the ortho-O-dimeric product as steric effects prevent the sandwich approach of two aryloxyl radicals necessary for C–C coupling.

Oxidative coupling of phenols. Part 7. Spin-density calculations on the phenoxyl radical

The calculation of the spin-density distribution and other properties of the phenoxyl radical by a variety of ab initio MO techniques is described. The relative importance of basis-set size to structural factors was investigated and the results indicate that the geometry of the radical is a more important feature in arriving at a satisfactory theoretical description of the spin-density distribution in the phenoxyl radical than is the basis set.

Oxidative coupling of phenols. Part 9. The role of steric effects in the oxidation of methyl-substituted phenols

MINDO/3 calculations indicate that for the coupling of 3,5-dimethylphenoxyl radicals the non-bonded methyl–methyl interactions cause the energy difference between the staggered (1b) and eclipsed (2b) geometries of approach to be greater than in the analogous coupling of phenoxyl radicals. The preferential and exclusive formation of the ortho-ortho-coupled products from the respective oxidations of 2,3-dimethylphenol and 2,3,5-trimethylphenol with di-t-butyl peroxide also support a mechanism, which proceeds viaa staggered transition state.

Oxidative coupling of phenols. Part 6. A study of the role of spin density factors on the product composition in the oxidations of 3,5-dimethylphenol and phenol

Oxidations of both 3,5-dimethylphenol and phenol with di-t-butyl peroxide at 140 °C gave as the major product the ortho-ortho-C–C coupled dimer, while oxidations with di-t-butyl peroxyoxalate at room temperature give much more of the ortho-para-C–C dimer. The results are not consistent either with the spin density distribution in the phenoxyl radical intermediates or with steric effects being the major factor which determines the product composition. It is proposed that the two phenoxyl radicals involved in coupling preferentially approach each other in a ‘sandwich-like’ manner with the oxygens in a 1,3-relationship.

Oxidative coupling of phenols. Part 8. A theoretical study of the coupling of phenoxyl radicals

A theoretical study is described of the stereochemistry of mutual approach of two phenoxyl radicals. Both the CNDO and MINDO/3 methods are used and Morse curves are calculated for each reaction where the reaction co-ordinate is the interplanar distance. From a number of possible stereochemistries the most favoured involves an initial coaxial sandwich geometry, which undergoes conformational changes as bond formation between the two radical species occurs. The most energetically favoured path, which is given by the staggered form of the rings, leads to ortho-para- and ortho-ortho-coupled products. Of lesser importance is a head-to-tail approach which can lead to either ortho-ortho-carbon coupling or para-oxygen coupling. The para-para- and ortho-para-couplings obtained from the eclipsed form are of still smaller significance.

Purification and characterization of dihydrogeodin oxidase from a fungal strain of Aspergillus terreus producing (+)-geodin.

Dihydrogeodin oxidase (DHGO), an enzyme catalyzing regio- and stereo-specific intramolecular phenol oxidative coupling reaction of dihydrogeodin to give (+)-geodin, was purified up to homogeneity. DHGO was shown to be a blue copper protein with an absorption maximum at 600 nm. The presence of copper atoms was confirmed by atomic absorption analysis. A molecular weight of 153, 000 was estimated for the oxidase and it was composed of two equal molecular weight subunits. DHGO had no phenolase activity and showed strict substrate specificity.

A spectrophotometric study of the reactions of the phenolic oxidative 1 coupling initiator py 4Cu 4Cl 4O 2 and of py 4Cu 4CI 6O with pyridine

The species py 4Cu 4CI 4O 2 is an active initiator for phenolic oxidative by dioxygen while its disproportionation product py 4Cu 4CI 6O is not. Spectrophotometric titration shows that the active complex has a very high relative affinity for pyridine, which is known to influence the distribution of products from copper-catalyzed phenolic oxidative coupling.

Biomimetic total synthesis of (−)-codeine

The opium alkaloid (−)-codeine was synthesized in eight steps from (±)-N-norreticuline R-(−)-norreticuline, obtained by resolution, was converted to (R)-N-trifluoroacetyl-6'-bromonorreticuline and the latter was subjected to phenolic oxidative coupling with a variety of aryliodoso complexes in dichloromethane. N-Trifluoroacetyl-1-bromonorsalutaridine prepared by this means was transformed to 1-bromosalutaridinol (as a mixture of epimers), and the latter were dehydrated separately to 1-bromothebaine with dimethylformamide dineopentyl acetal. Hydrolysis to 1-bromocodeinone, followed by reductive removal of Br with LAH, afforded (−)-codeine.

Immobilization of a homogeneous macromolecular copper catalyst for the oxidative coupling of phenols

In order to combine the advantages of both homogeneous and heterogeneous catalysis, an immobilized macromolecular copper catalyst was prepared by radical graft copolymerization of styrene and 4-vinylpyridine on nonporous silica spheres and by subsequent complex formation of copper(II) chloride with these grafted macromolecular pyridine ligands. The oxidative coupling of 2,6-disubstituted phenols was chosen to test the catalytically active species, i.e. dihydroxo-bridged copper dimers. The immobilized polymeric catalysts show a remarkable activity: reaction rates up to 70% compared to nonbound macromolecular analogues can be achieved. Moreover, they can easily be re-used several times without loss of activity, while the mechanism of the coupling reaction is not influenced.

Spirans. Part 15. The effect of ring size upon the regioselective oxidative coupling of heterocyclic phenols

The oxidation of 2,3-dihydro-2,2,4,6,7-pentamethylbenzofuran-5-ol (7b) by alkaline potassium hexacyanoferrate(III) gives a complex mixture from which three products have been isolated and identified; all result from oxidation at the 6-methyl group only. Although unidentified products may have resulted from oxidation at the 4-methyl group, the evidence supports the view that the size of the heterocyclic ring determines the regioselectivity. The products are 2,2′,3,3′-tetrahydro-2,2,2′,2′,4,4′,7,7′-octamethyl-6,6-ethylenebisbenzofuran-5,5′-diol (8), which gives the spiran (11), 2,2′,3,3′,7′,8′-hexahydro-2,2,2′,2′,4,4′,7′,9-octamethyl-6H-pyrano[2,3-f]benzofuran-6-spiro-6′(5′H)-benzofuran-5′-one, upon further oxidation, and the related trimer (12), the structure of which is partly disclosed by hydrolysis (by silica) of the acetal grouping. The size of the heterocyclic ring has little effect upon the ease of sigmatropic rearrangement in the spiran (11), but influences the ease with which this dissociates to give a quinone methide and thence the trimer (12).With mild base 4-chloromethyl-2,3-dihydro-2,2,6,7-tetramethylbenzofuran-5-ol (7e) gave a trimer isomeric with compound (12).