Synthesis of musafluorone: a naphthoxanthenone isolated from Musa acuminata

5-Methoxy-3H-naphtho[2,1,8-mna]xanthen-3-one (musafluorone, 1), the only naphthoxanthenone reported so far from Musaceae, was synthesized starting from 2-naphthol in nine steps and resulted in an overall yield of 3%. Grignard addition of phenylmagnesium bromide to 4-methoxyperinaphthenone afforded the corresponding 4-methoxy-9-phenylphenalenone which, after epoxidation and methyl transposition, was subjected to a photochemical cyclization procedure to furnish 1.     

A review of reaction detection in HPLC

Summary In the past decade, reaction detection has rapidly gained importance as a means to improve the sensitivity and selectivity of detection in HPLC. Today, most attention is being paid to post-column reaction detection with final analysis via fluorescence monitoring. Novel developments involve the use of solid-phase reactors for reagent addition or catalysis (ion-exchange resins, immobilized enzymes), and the increasing use of systems based on peroxyoxalate chemiluminescence detection. The rapidly growing number of reported applications indicates that commercialization of reaction-detection equipment is urgently needed.     

Laser induced fluorescence and photochemical derivatization for trace determination of camptothecin

Laser-excited fluorescence was used for the selective determination of camptothecin in samples containing anti-cancer camptothecin-analogs (irinotecan and topotecan). The selectivity of the method was based on the UV photochemical derivatization in basic solution which increased the analyte fluorescence (337/450 nm) and eliminated fluorescence from the two campthotecin-analogs. The influence of UV exposure time and sodium hydroxide concentration was studied using an experimental design. Limit of detection was 4 × 10⁻¹⁰ mol L⁻¹ with linear fluorescence response up to 1 × 10⁻⁶ mol L⁻¹. Average recoveries of camptothecin (added to the samples to simulate a contamination) were 92 ± 4 and 94 ± 6% (n = 3) respectively in irinotecan and topotecan based pharmaceuticals.     

光化学荧光分析法测定头孢氨苄的研究

在ｐＨ４．０的缓冲溶液中，头孢氨苄在紫外光照射下能发生光化学反应，形成具有荧光的产物，λｅｘ为３４５ｎｍ，λｅｍ为４３２ｎｍ。在头孢氨苄浓度为０．１－４．０μｇ／ｍｌ范围内，荧光强度与浓度呈良好的线性关系，由此建立了头孢氨苄的光化学荧光测定法。方法的检出限为０．０１μｇ／ｍｌ，相对标准偏差为０．９３％。本法简便，快速且灵敏度高，可用于尿液中头孢氨苄含量的测定。     

Photochemische reaktionen von übergangsmetall-organyl-komplexen mit Olefinen XII. Photochemisch induzierte [5 + 2, 3 + 2]-cycloadditionen von alkinen an tricarbonyl-η-cyclohexadienly-mangan

Upon UV irradiation in hexane at 243 K tricarbonyl-η⁵-cyclohexadienyl-manganese (1) and two equivalents of 2-butyne (2) or diphenylacetylene (4) yield in successive [5 + 2, 3 + 2] cycloadditions tricarbonyl-η^2:2:1-1,2,3,10-tetramethyl-tricyclo[5.2.1.0^4,9]-deca-2,5-dien-10-yl-manganese (6), or tricarbonyl-η^2:2:1-1,2,3,10-tetraphenyl-tricyclo[5.2.1.0^4,9]-deca-2,5-dien-10-yl-manganese (8), respectively. 3-Hexyne (3) reacts with 1 under the same conditions by successive [5 + 2, 3 + 2] cycloadditions and 1,4-H-shift to tricarbonyl-η^2:2:1-1,2,3-triethyl-10-ethylidene-tricyclo[5.2.1.0^4,9]dec-2-en-5-yl-manganse (7). Identical products are also obtained when 1 is first irradiated in THF at 208 K and the thermolabile intermediate, dicarbonyl-η⁵-cyclohexadienyl-tetrahydrofurane-manganese (11), is treated with an excess of the alkynes 2–4. In contrast, bis(trimethylsily)acetylene (5) substitutes photochemically in 1 only a CO ligand to yield dicarbonyl-η⁵-cyclohexadienyl-η²-bis(trimethylsily)Acetylene-manganese (9). The crystal and molecular structure of 7 was determined by an X-ray diffraction analysis. Complex 7 crystallizes in the triclinic space group , a = 822.6(2) pm, B = 882.5(2) pm, C = 1344.6(2) pm, = 92.36(2)°, β = 107.13(2)°, γ = 99.71(2)°, V = 0.9152(3) nm³, Z = 2. The complexes 6–9 were studied in solution by IR and NMR spectroscopy. The structures of 6,8 and 9 were elucidated from the NMR spectra. A possible formation mechanism for the complexes 6–9 will be discussed.     

Rhodium-carbonyl complexes with a quinolyl functionalized Cp-ligand: synthesis and photochemical activation

Dicarbonyl[η⁵-2,3,4,5-tetramethyl-1-(8-quinolyl)cyclopentadienyl]rhodium(I) (1) was prepared by the reaction of [Rh(CO)₂Cl]₂ with 2,3,4,5-tetramethyl-1-(8-quinolyl)cyclopentadienyl-potassium. Irradiation of 1 in chloroform or dichloromethane as solvent leads to the formation of dichloro[η⁵-2,3,4,5-tetramethyl-1-(8-quinolyl)cyclopentadienyl]rhodium(III) (2). When Rh₆(CO)₁₆ is present, the cluster adds to the 8-quinolyl-cp-rhodium fragment and the compound [η⁵-2,3,4,5-tetramethyl-1-(8-quinolyl)cyclopentadienyl]rhodium-di-μ-carbonyl-hexarhodiumtetradecacarbonyl (3) is formed in 65% yield. The coordination sphere of the rhodium(III) atom in compound 2 and of the rhodium(I) atom in 3 is completed by a coordination of the quinolyl moiety. This was revealed by NMR spectroscopy as well as by X-ray analyses.     

Photochemical control of network structure in gels and photo-induced changes in their viscoelastic properties

Poly(amide acid) gels containing photosensitive azobenzene groups in the main chain have been synthesized and their viscoelastic properties before and after light irradiation have been investigated by dynamic viscoelasticity measurements. It was found that 405 nm light induced a local volume change and a two-fold increase in the storage modulus of the gels. We discuss the change in storage modulus upon light irradiation quite simply in terms of classical rubber elasticity theory, which cannot explain this large increase in storage modulus. The photo-induced increase in storage modulus may result from an increase in entanglement interactions of topological constraints fixed in the network structure, caused by photoisomerization of the azobenzene moieties. We suggest that topological constraints in the network structure of the gels were realized by light irradiation and calculate the resulting slip link ratio (index of the topological constraints) in the gel network.     

The dimerization and photochemical rearrangement of pentacyclo-[5.4.0.0.0.0]undecane-8-thione

Pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecan-8-one 1 is readily sulfurated into pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecane-8-thione 2 with Lawesson’s reagent in dry THF. Upon standing at ambient temperature the thione 2 formed the corresponding thio-dimer 3 within 10 days. When the thio-dimer 3 was exposed to oxygen and ultraviolet light an unexpected photochemical oxidation and rearrangement took place to form the stable disulfenate 5.     

Synthesis, photophysical and photochemical properties of highly soluble phthalocyanines substituted with four 3,5-dimethylpyrazole-1-methoxy groups

The synthesis and characterization of new peripherally tetra-3,5-dimethylpyrazole-1-methoxy substituted metal-free (4), zinc (5), nickel (6), cobalt (7), copper (8) and lead (9) phthalocyanines are described for the first time in this study. The photophysical (fluorescence quantum yields and fluorescence lifetimes) and photochemical (photodegradation and singlet oxygen quantum yields) properties of metal-free (4), zinc (5) and lead (9) phthalocyanines are studied in dimethylsulfoxide (DMSO). Nickel (6), cobalt (7) and copper (8) phthalocyanines (6-8) did not evaluate for this purpose due to transition metal and paramagnetic behavior of central metals in the phthalocyanine cavity. The fluorescence quenching behavior of metal-free (4), zinc (5) and lead (9) phthalocyanines are also investigated. The fluorescence emissions of these phthalocyanines are effectively quenched by 1,4-benzoquinone in DMSO.     

Crystal structure,electrochemical and photochemical studies of the trans-[Fe(cyclam)(NO)Cl]Cl2 complex (cyclam = 1,4,8,11-tetraazacyclotetradecane)

The trans-[Fe(cyclam)(NO)Cl]Cl₂ complex was synthesized by the reaction of cis-[Fe(cyclam)Cl₂]Cl with NO gas. The X-ray structure of the complex showed that the [Fe–NO] moiety is linear, consistent with the NO⁺ character of the nitric oxide ligand. This suggestion was reinforced by the IR data, which showed the νNO at 1888 cm⁻¹. The cyclic voltammogram of the trans-[Fe(cyclam)(NO)Cl]²⁺ complex presented three electrochemical processes at −0.70, 0.08 and 0.40 V versus Ag/AgCl. The first and last redox processes are centered at the NO ligand, whereas the second is characteristic of the generated aqua species, trans-[Fe(cyclam)Cl(H₂O)]²⁺. Upon irradiation at 330 nm, pH 3.4, the title complex releases the NO moiety with the concomitant generation of the trans-[Fe(cyclam)(H₂O)Cl]⁺ complex as suggested by electronic and IR spectroscopy as well as by cyclic voltammetry technique.