Study on Semi-Glycinecresol Red complexes with bivalent metal ions

Semi-Glycinecresol Red (SGCR or H(3)SGCR) was purified by means of chromatography on cellulose and by cation-exchange. A potentiometric, spectrophotometric and ESR study on the complex formation equilibria of several bivalent metal ions with SGCR was performed. The acid-base and metal-ligand stoichiometries were determined, and the formation constants, lambda(max) and absorptivities of the visible-region absorption spectra of the corresponding proton and metal complexes were determined. The copper complexes were examined by ESR spectroscopy. Each metal ion was found to form the 1:1 and 1:2 (metal:ligand) complex species, MSGCR(-) and M(SGCR)(4-)(2), in alkaline solution. However, only Cu(II) was found to form the protonated complexes, CuHSGCR and Cu(HSGCR)(2-)(2), in weakly acidic media. SGCR is suitable as an indicator for Cu(II) in a weakly acidic solution and for Cu(II), Zn(II) and Pb(II) in alkaline solution.     

Stereospecific 2-vinylcyclohexanol formation via internal attack of an allylsilane moiety on an aldehyde group

Acid catalyzed cyclization of ($\text{E}$)-HCO-(CH₂)-₄-CH=C(Me)-CH(SPh)SiMe₃ affords $\text{cis}$-2-substituted cyclohexanol, while ($\text{Z}$) compound affords the $\text{trans}$ isomer. Those cyclized products are transformed to the corresponding α-methyl γ-lactones.     

Formation of manganese-alkyne complexes mediated by trialkylmanganates and their application

Treatment of dodec-6-yne with triallylmanganate in the presence of 1,3,5-trimethylbenzene provides (Z)-dodec-6-ene. An addition of D₂O before quenching the reaction affords the corresponding dideuterated alkene. The result suggests the existence of the manganese-alkyne complex as an intermediate. Treatment of methyl propargyl ethers as alkynes with tributylmanganate generates propargylmanganese species. The reaction of non-2-ynyl tetrahydropyran-2-yl ether with tributylmanganate provides tetradec-7-yn-1,5-diol and 6-hexylocta-6,7-dien-1,5-diol.     

Intramolecular cyclization mediated by silylmetalation of acetylenes with PhMe2SiMgMe/CuI and radical nature of the reagent

Whereas CuI catalyzed silylmagnesation of the tosylate of 5- hexyn-l-ol with the title reagent affords dimethylphenylsilylmethylenecyclopentane exclusively, the mesylate of 3-butyn-l-ol gives a mixture of unexpected silylcyclobutene and cyclopropylidene derivative.     

Regioselective stannylmetalation of acetylenes in the presence of transition-metal catalyst

The reaction of terminal acetylenes with Bu₃SnMgMe, Bu₃SnA1Et₂, or (Bu₃Sn)₂Zn in the presence of various transition-metal catalysts provides vinylstannanes in good yields. Whereas copper catalysed stannylmagnesation of 4-benzyloxy-1-butyne gives (E)-4-benzyloxy-1-tributylstannyl-1-butene exclusively, palladium catalysed stannylzincation affords 4-benzyloxy-2-tributylstannyl-1-butene preferentially.     

Biaryl synthesis from two different aryl halides with tri(2-furyl)germane

[reaction: see text] The coupling reaction of germanium compounds with aryl halides has been developed. The Pd(0)-catalyzed reaction of aryl halides with tri(2-furyl)germane provides aryltri(2-furyl)germanes in good yield. The cross-coupling reaction of aryltri(2-furyl)germanes with aryl halides is achieved. This allows facile synthesis of unsymmetrical biaryls from two different aryl halides.     

A rapid and reliable solid-phase extraction method for high-performance liquid chromatographic analysis of opium alkaloids from papaver plants

A rapid and reliable solid-phase extraction method for HPLC analysis of opium alkaloids from Papaver plants was established. Fifty mg of dried and powdered plant sample was extracted with 5 ml of 5% acetic acid for 30 min under sonication. After centrifugation, 3 ml of the supernatant was loaded on a reversed-phase cation-exchange solid-phase extraction cartridge. After seriate washings with 0.1 M hydrochloric acid and methanol, alkaloids were eluted with a mixture of 28% ammonia and methanol (1:19). The eluate was concentrated under nitrogen stream at 40 degrees C and the residue was dissolved in 50% aqueous methanol for high performance liquid chromatographic analysis. With this solid-phase extraction method, the recovery of morphine, codeine, oripavine, thebaine, papaverine, noscapine and sanguinarine was from 99.94 to 112.18% when the standard alkaloids were added to the plant samples. Opium alkaloids of a variety of genus Papaver plants cultivated in a field and phytotron were analyzed by this method.     

Determination of triethylenetetramine in plasma of patients by high-performance liquid chromatography

A sensitive and simple fluorometric method for the determination of N,N'-bis(2-aminoethyl)-1,2-ethanediamine dihydrochloride (triethylenetetramine) in human plasma by high-performance liquid chromatography is described. Free triethylenetetramine (TETA) obtained by passing the TETA-copper chelate compound through a solid-phase cation exchange resin was converted to its fluorescamine derivative in the presence of ethylenediaminetetraacetic acid to mask the interfering metal ions in the reaction solution, and the derivatives were separated on a nitrile high-performance liquid chromatograph column (Nucleosil 5-CN) using isocratic elution. The plasma levels of TETA were measured in eight patients receiving treatment for excess copper. Absorption rates of TETA were relatively slow and the peak levels were significantly different among patients. The bioavailability of TETA in the rat was also examined and the ratio of intestinal absorption was extremely low.     

Carboncarbon bond formation by cross-coupling of enol phosphates with organoaluminium compounds catalyzed by palladium(O) complex

Trialkylaluminium-mediated alkylation of enol phosphates under the CO bond cleavage is performed stereospecifically in the presence of a catalytic amount of Pd(PPh₃)₄. Alkenylation and alkynylation are also described.     

Nucleophilic aromatic substitution reaction of nitroarenes with alkyl- or arylthio groups in dimethyl sulfoxide by means of cesium carbonate

Treatment of nitroarenes having electron-withdrawing groups at the ortho or para position with alkanethiol in the presence of cesium carbonate in dimethyl sulfoxide at 25 °C leads to nucleophilic displacement of the nitro group with the alkylthio group. Cesium carbonate is superior to other bases such as potassium carbonate, sodium carbonate, and triethylamine. The cesium-mediated nucleophilic aromatic substitution reaction provides a mild yet powerful and user-friendly protocol for the synthesis of aryl sulfides.