Regioselective Oxidative Coupling Research Articles

ChemInform Abstract: Palladium‐Catalyzed Regioselective Oxidative Coupling of Indoles and One‐Pot Synthesis of Acetoxylated Biindolyls.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Biosynthesis of Resveratrol Dimers by Regioselective Oxidative Coupling Reaction

A wide array of natural resveratrol dimers was prepared by theregioselective oxidative coupling reaction of 3,5-di-( TERT--butyl)resveratrol usingseveral types of metal oxidants (Ag 2 O, Ag 2 CO 3 ,MnO 2 , and FeCl 3 ˙6H 2 O)in different solvent systems (benzene-acetone and dichloromethane).Subsequent debutylation of these coupling products resulted in racemicpallidol and ampelosin F.

Palladium-Catalyzed Regioselective Oxidative Coupling of Indoles and One-Pot Synthesis of Acetoxylated Biindolyls

Mild conditions have been developed to achieve Pd-catalyzed homocoupling of indoles with excellent regioselectivity in the presence of Cu(OAc)(2) x H(2)O in DMSO at room temperature in high efficiency. This method provides a simple route to 2,3'-biindolyls from the electron-rich to moderately electron-poor indoles. The reaction tolerates the bromide substituent on indoles. In addition, a one-pot approach to C3-position acetoxylated biindolyls is realized via palladium catalysis by the use of AgOAc under oxygen atmosphere as oxidants.

Highly Regioselective Palladium-Catalyzed Oxidative Coupling of Indolizines and Vinylarenes via C−H Bond Cleavage

A highly regioselective oxidative coupling reaction between indolizines and vinylarenes has been accomplished in the presence of palladium catalysts to give only the branched alpha-product in high efficiency. The regioselectivity is promoted significantly by bidentate nitrogen ligands.

Highly Regioselective Catalytic Oxidative Coupling Reactions: Synthetic and Mechanistic Investigations.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Highly Regioselective Catalytic Oxidative Coupling Reactions: Synthetic and Mechanistic Investigations

A highly efficient and regioselective Pd-catalyzed method for the oxidative coupling of arylpyridine derivatives is reported. Remarkably, the reactions proceed at room temperature and are compatible with diverse functionalities, including aryl halides and thiophenes. Mechanistic studies suggest that these transformations proceed via a previously unprecedented mechanism involving two different pyridine-directed C-H activation reactions-one at a PdII center and one at PdIV.

Regioselective Oxidative Coupling Approach to the Synthesis of (±)-Matairesinol and (±)-Secoisolariciresinol

An efficient method for the synthesis of (±)-matairesinol and (±)-secoisolariciresinol is presented. By using 5-(tert-butyl)ferulic acid as a precursor, a regioselective oxidative coupling step was realized, which gave the desired coupling product in much higher yield (91%) than the literature value (ca. 20%).

An efficient method for the synthesis of lignans

An efficient approach for the synthesis of several types of lignans (dibenzylbutanediols, dibenzylbutanes, substituted tetrahydrofurans, aryldihydronaphthalenes, arylnaphthalenes, and aryltetralins) was developed. The regioselective oxidative coupling of ethyl ferulate was used as the key step.

A heartwood pigment in Dalbergia cell cultures

In an extensive survey of the genera Baphia, Caesalpinia, Dalbergia, Haematoxylon, and Pterocarpus, we have identified a number of species whose cell cultures accumulated pigments similar to those in heartwood. Thirteen rosewood ( Dalbergia) species produced a purple quinonemethide pigment in the callus that was apparently identical between the species. The pigment was first purified from D. retusa cell culture and its structure was elucidated by mass, infrared, and detailed 1H and 13C NMR and NOE spectroscopic studies including 2D experiments (COSY, NOESY, HMQC, and HMBC). Retusapurpurin A ( 1a) is a C 30 isoflavan of novel skeleton whose formation can be rationalized to occur via regioselective oxidative coupling of an isoflavan to 4,4′-dihydroxy-2′-methoxychalcone. Retusapurpurin A was also isolated from D. parviflora heartwood and cell culture indicating that stress metabolism pathways that are shared with heartwood-type secondary metabolism subpathways are initiated in Dalbergia cell cultures. Therefore, Dalbergia cell cultures afford a good model system for studying heartwood-type metabolic differentiation.

Phenyliodine(III) bis(trifluoroacetate) mediated synthesis of phenanthro[9, 10- d] fused isoxazoles and pyrimidines

A novel protocol for the PIFA mediated regioselective oxidative coupling of 4, 5-diaryl substituted isoxazoles and pyrimidines leading to new phenanthro[9, 10- d]heterocyclic systems is reported. The oxidative coupling of diarylisoxazoles and diarylpyrimidines is accomplished in the presence of phenyliodine(III) bis(trifluoroacetate) providing a concise route to new phenanthro[9, 10- d]fused heterocyclic systems. [Display omitted]

Novel oxidative phenol-coupling reaction with phosphomolybdic acid on silica gel support: Regioselective biomimetic synthesis of dimeric phenanthrene derivatives

Biomimetic synthesis of the naturally occurring dimeric phenanthrene derivatives, cirrhopetalanthrin ( 3a) and flavanthrin ( 7a), and their structural analogues 3c, 3e, 5a and 7c was achieved in very high yields by regioselective oxidative coupling of their respective phenolic monomers 2a, 6a, 2c, 2e, 4a and 6c with phosphomolybdic acid on a silica gel support. Unlike coelonin ( 6a) and lusianthridin ( 6c), 2,7-dihydroxy-3,4,6-trimethoxy-9,10-dihydrophenanthrene ( 6e) gave, on similar oxidation, the phenanthrene dimer 3e. Instead of the expected 9,10-dihydrophenanthrene dimer 7e. β-Naphthol afforded the corresponding 1,1′-dimer 1a in almost quantitative yield. The structures of the new dimeric compounds were established from various spectral data of the compounds and their respective acetyl derivatives.

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).