Stipitatic acid: synthesis via cyclopropanated quinones

A new synthesis of stipitatic acid incorporating a cyclopropanated quinone intermediate is reported.     

A biomimetic synthesis of polycyclic quinones

Various polycyclic quinones were synthesized by the intramolecular condensation of polyketides followed by the air-oxidation.     

Cycloaddition reaction of zirconacyclopentadienes to quinones: synthesis of higher para-quinones

Efficient synthetic approaches to higher para-dihydroquinones and -quinones have been developed through zirconium/CuCl-mediated cycloaddition reactions of two alkynes and quinone in a one-pot procedure.     

Laccase-generated quinones in naphthoquinone synthesis via Diels-Alder reaction

The tandem synthesis of naphthoquinones was conducted from the reaction of laccase-generated quinones and acyclic dienes via Diels-Alder reaction. This reaction was carried out under mild condition in aqueous medium and yielded naphthoquinones up to 80%. In addition, the effect of solvent was also investigated and water was shown to be optimal for this reaction.     

Electrochemical synthesis of quinones and other derivatives in biphasic medium

Electrochemical synthesis of quinones has been attempted from phenols, 1,4-dihydroxybenzenes, 1,4-dihydroxynaphthalenes and related compounds using biphasic media. Excellent yields of quinones (98%) or brominated diols have been achieved with good current efficiency. Reuse of the electrolyte without any modification and quantitative conversion of substrate with theoretical amount of current are the advantages of this method.     

Enantioselective synthesis of (+)-royleanone from sulfinyl quinones

A convergent enantioselective synthesis of (+)-royleanone (1) is described starting from enantiomerically pure (S)-3-hydroxy-2-isopropyl-5-tert-butylsulfinyl-p-benzoquinone, which is readily available from 3-isopropyl-1,2,4-trimethoxybenzene and 1,3,3-trimethyl-2-vinylcyclohexene. The key step is a tandem asymmetric Diels-Alder reaction/pyrolytic sulfoxide elimination process.     

The development of an organotransition metal synthesis of quinones

A new and very general synthesis of quinones is described from conception to the current state of maturity. The chemistry relies on a convergent joining of a transition metal complex and an alkyne to provide benzoquinones (from maleoylmetal complexes) and naphthoquinones (from phthaloylmetal complexes). Significant aspects of this chemistry are its generality (terminal, internal, electron rich, and electron deficient alkynes react), its mildness (reactions can be run between room temperature and 80°) and its functional group compatibility (aldehydes, ketones, esters, nitriles, olefins, halides acetals, ketals, etc. survive).     

Vinyl quinones as Diels-Alder dienes: concise synthesis of (-)-halenaquinone

A concise asymmetric synthesis of (-)-halenaquinone is described. The synthesis features a diastereoselective Heck cyclization to set a quaternary center as well as a novel intramolecular inverse-electron-demand Diels-Alder reaction involving a vinyl quinone. The synthesis is highly convergent and features a minimal amount of protecting group manipulations.     

Triptycene quinones in synthesis: preparation of triptycene cyclopentenedione and its reactivity as a dienophile

Triptycenene quinone 1 was converted to triptycene cyclopentenedione 5 through hydroxyquinone-phenyliodonium ylide formation and thermal ring contraction of the latter. Cyclopentenedione 5 reacts as a dienophile and as a dipolarophile with dienes and nitrile oxides, affording polycyclic adducts bearing the triptycene moiety.     

The reaction of diphenyllithioarsine with quinones and aromatic ketones: a convenient synthesis of tetraphenyldiarsine

Diphenyllithioarsine is oxidized by aromatic ketones and quinones to tetraphenyldiarsine. These reactions were studied by means of EPR spectroscopy in order to ascertain the course of the reaction. Tetraphenyldiarsine was charcterized by its mass spectrum, PMR spectrum, and conversion to diphenyldimethylarsonium iodide.     

A microwave-assisted synthesis of phenanthroperylene quinones as exemplified with hypericin

The synthesis of hypericin, one of the most important phenanthoperylene quinones used in photodynamic therapy, could be highly improved by using either a microwave-assisted dimerization of emodinanthrone, or a mixed dimerization of emodinanthrone with emodin in the presence of potassium t-butoxide as the key-step.     

The synthesis of some new rhodium π-complexes with quinones

Conclusions New-complexes of rhodium with quinones were prepared and their structures were determined.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1898–1900, August, 1968.The authors thank G. A. Nikiforov for the gift of 2,6-di-t-butylbenzoquinone-1,4 and I. F. Leshchevaya for taking and discussing the NMR spectra.     

Metal carbonyl derivatives of sulfur-containing quinones and hydroquinones: synthesis, structures, and electrochemical properties

The reaction of CpMoMn(mu-S(2))(CO)(5), 1, with 1,4-benzoquinone in the presence of irradiation with visible light yielded the quinonedithiolato complex CpMoMn(CO)(5)(mu-S(2)C(6)H(2)O(2)), 2. The new complex CpMoMn(CO)(5)(mu-S(2)C(6)Cl(2)O(2)) (4) was synthesized similarly from 1 and 2,3-dichloro-1,4-benzoquinone. Compounds 2 and 4 were reduced with hydrogen to yield the hydroquinone complexes CpMoMn(CO)(5)[mu-S(2)C(6)H(2)(OH)(2)], 3, and CpMoMn(CO)(5)[mu-S(2)C(6)Cl(2)(OH)(2)], 5. UV-vis irradiation of solutions of Fe(2)(CO)(6)(mu-S(2)) and 1,4-benzoquinone yielded the hydroquinone complex Fe(2)(CO)(6)[mu-S(2)C(6)H(2)(OH)(2)], 6. Compound 6 was oxidized to the quinone complex Fe(2)(CO)(6)(mu-S(2)C(6)H(2)O(2)), 7, by using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. Substitution of the CO ligands on 6 by PPh(3) yielded the derivatives Fe(2)(CO)(5)(PPh(3))[mu-S(2)C(6)H(2)(OH)(2)], 8, and Fe(2)(CO)(4)(PPh(3))(2)[mu-S(2)C(6)H(2)(OH)(2)], 9. The electrochemical properties of 3, 5, 6, 8, and 9 were measured by cyclic voltammetry. The molecular structure of each of the new compounds 2-9 was established by single-crystal X-ray diffraction analyses.     

Phenoxazine polymers: synthesis and structure

Phenoxazine polymers were obtained for the first time under conditions of chemical oxidative polymerization in aqueous alcohols and in an interphase process. The interphase process gave products with the higher molecular weight. Dependencies of the yields and degree of polymerization of phenoxazine from polymerization method, concentration of reactants, their ratio, reaction temperature and time, as well as chemical structures of the obtained polymers depending on the synthesis conditions, were studied. The polyphenoxazine chain growth is accomplished by the C-C-addition at the para-position of the phenyl rings with respect to nitrogen. Even when an excess of oxidant was used, the polyphenoxazine structure has only phenyleneamine units. The polymers obtained are amorphous and thermally stable.     

Bismuth-ferrocene carboxylates: synthesis and structure

The reaction of ferrocenedicarboxylic acid with triphenylbismuth in a 1?:?1 ratio under solvothermal conditions afforded the 1D coordination polymer [Bi(2)(μ(2)-η(2)-OOCFcCOO-μ(2)-η(2))(η(2)-OOCFcCOO-η(2))(μ(2)-η(2)-OOCFcCOO-η(2))](n) (1). In this polymer two types of bismuth centers (hepta- and octacoordinate) are present and are interconnected by the bridging coordination of ferrocene dicarboxylate ligands. The reaction of ferrocenecarboxylic acid with triphenylbismuth in a 1?:?3 ratio, in toluene, under refluxing conditions, afforded the 1D coordination polymer [Bi(μ(2)-η(2)-FcCOO)(η(2)-FcCOO)(2)](n) (2). In the solid state, 2 exists as a helical polymer, where the inner bismuth chain is enclosed by an external sheath of ferrocene carboxylate ligands. In solution, however, 2 decomposes into the monomeric repeat unit [Bi(FcCOO)(3)] which is indicated by ESI-MS as well as cyclic voltammetric studies. Thus, a single, quasi-reversible redox event is seen for 2 in solution. The reaction of triphenylbismuth with ferrocenecarboxylic acid in a 1?:?1 stoichiometry afforded the molecular dimer [Bi(2)(μ(2)-η(2)-FcCOO)(2)(η(2)-FcCOO)(4)(H(2)O)(4)]·(2FcCOOH) (3). Compounds 1-3 reveal rich supramolecular architectures in the solid state as a result of the presence of C-HO, C-Hπ and ππ interactions.     

Mostueine: synthesis and structure revision

A total synthesis of mostueine (1) based upon the intramolecular alkylation of the indole nitrogen is described. A revision of the reported sterochemistry of mostueine to 3SR, 19RS as elucidated by synthesis and NOE data is disclosed.     

Reactions of quinones with some aryl phenols and synthesis of new quinone derivatives

In the present study, the reactions of p-chloranil (1a) and 2,3-dichloro-1,4-naphthoquinone (DCNQ) (1b) with some aryl phenols were investigated. The structures of all compounds were characterized using spectroscopic methods (FT-IR, ¹H NMR, ¹³C NMR, and MS) and microanalysis. The electrochemical behaviors of some benzoquinone and naphthoquinone derivatives have also been investigated in unbuffered aprotic solutions.