Asymmetric synthesis of 1-hydroxyindolizidines, biosynthetic precursors to the toxic indolizidine alkaloids slaframine and swainsonine

An enantioselective synthesis of 1-hydroxyindolizidines (1 and 2) from racemic N-benzyloxycarbonyl-3-hydroxy-4-pentenylamine (3) by following the Sharpless kinetic resolution, intramolecular amidomercuration, and radical Michael addition as key steps is described.     

Crown Ethers as Synergist in the 2-Thenoyltrifluoroacetone Extraction of Lanthanoids in 1,2-Dichloroethane

Summary. The solvent extraction of 14 trivalent lanthanoid ions (Ln ³⁺) from a nitrate medium into 1,2-dichloroethane containing 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (HTTA) was investigated at 25.0°C. The extraction of Ln(TTA)₃ species was confirmed and the extraction constants were determined. The extraction of Ln with the synergistic mixture of HTTA and a crown ether (CE: 12-crown-4, 18-crown-6, cyclohexano-18-crown-6 or benzo-18-crown-6) was also investigated at 25.0°C. The 1:1 adducts of the complex and crown ether, Ln(TTA)₃·(CE) are formed for all the lanthanoid ions and the CEs used in this study. The formation constants, β_add, of the adduct Ln(TTA)₃·(CE) from Ln(TTA)₃ in the organic phase were determined by nonlinear least-squares method. The stabilities and structures of the formed adducts were discussed with respect to the cavity size, steric effect, and basicity of the CE.     

Incorporation of nonadiabatic transition into wave-packet dynamics

Nonadiabatic wave-packet dynamics is factorized into purely adiabatic propagation and instantaneous localized nonadiabatic transition. A general formula is derived for the quantum-mechanical local nonadiabatic operator which is implemented within the framework of the R-matrix method. The operator can be used for incorporating the nonadiabatic transition in semiclassical wave-packet dynamics.     

Rhodium-catalyzed arylation using arylboron compounds: efficient coupling with aryl halides and unexpected multiple arylation of benzonitrile

[reaction: see text]. The Suzuki-Miyaura-type cross-coupling of arylboron compounds with aryl halides proceeds efficiently in the presence of a rhodium-based catalyst system to produce the corresponding biaryls. Furthermore, it has unexpectedly been observed that the treatment with benzonitrile under similar conditions brings about its multiple arylation, in which nucleophilic arylation on the cyano group and subsequent ortho arylation via C-H bond cleavage are involved.     

Structure and photoelectrochemical properties of nanostructured SnO2 electrodes deposited electrophoretically with the composite clusters of porphyrin-modified gold nanoparticle with a long spacer and fullerene

Structure and photoelectrochemical properties of nanostructured SnO₂ electrodes deposited electrophoretically with the composite clusters of porphyrin-modified gold nanoparticle with a long, flexible spacer and C₆₀ molecules have been examined to obtain basic information on the development of organic solar cells with a high performance. The photoelectrochemical system with the long, flexible spacer between the porphyrin and the gold nanoparticle in the porphyrin-modified gold nanoparticle exhibited comparable external quantum yield in the UV-vis regions relative to porphyrin-modified gold nanoparticle with a relatively short spacer—C₆₀ composite reference system. These results demonstrate that a suitable spacer to incorporate C₆₀ molecules efficiently between the porphyrins in porphyrin-modified gold nanoparticles is a prerequisite for improving the performance of porphyrin and fullerene-based organic solar cells.     

A new method for the synthesis of novel 6-quinoxalinylpyrazolo[5,1-c][1,2,4]triazines

The reaction of the quinoxaline 1 with 4-ethoxycarbonyl-1H-pyrazole-5-diazonium chloride 7 at room temperature gave 3-[α-(4-ethoxycarbonyl-1H-pyrazol-5-ylhydrazono)methoxycarbonylmethyl]-2-oxo-1,2-dihydroquinoxaline 8. The pmr spectrum of 8 in deuteriodimethylsulfoxide supported the presence of two tautomers 8-I and 8-II. Refluxing of 8 in N,N-dimethylformamide or acetic acid resulted in cyclization to afford 8-ethoxycarbonyl-4-oxo-3-(3-oxo-3,4-dihydroquinoxalin-2-yl)-1,4-dihydropyrazolo[5,1-c][1,2,4]triazine 9. Compound 9 was also obtained directly by the reaction of 1 with 7 under reflux in better yield. The reaction of 9 with hydrazine hydrate provided the hydrazinium salt 10 , while the reactions of 9 with triethyl and trimethyl orthoformates in the presence of 1,8-diazabicyclo[5,4,0]-7-undecene produced 8-ethoxycarbonyl-4-ethoxyl-3-(3-oxo-3,4-dihydroquinoxalin-2-yl)pyrazolo[5,1-c][1,2,4]triazine 11a and 8-ethoxycarbonyl-4-methoxyl-3-(3-oxo-3,4-dihydroquinoxalin-2-yl)pyrazolo[5,1-c][1,2,4]triazine 11b , respectively. The chlorination of 11a with phosphoryl chloride gave 3-(3-chloroquinoxalin-2-yl)-8-ethoxycarbonyl-4-ethoxylpyrazolo[5,1-c]-[1,2,4]triazine 12 , whose reaction with morpholine afforded 8-ethoxycarbonyl-4-ethoxyl-3-[3-(morpholin-4-yl)-quinoxalin-2-yl]pyrazolo[5,1-c][1,2,4]triazine 13.     

Some chemical transformations of 7a-cyanohexahydro-1H-pyrrolizine into 7a-substituted hexahydro-1H-pyrrolizines

Chemical transformations of 7a-cyanohexahydro-1H-pyrrolizine ( 2 ) into 7a-substituted hexahydro-1H-pyrrolizines are described. In the reaction of 2 with lithium aluminum hydride, the orientation of the lone pair of the bridgehead nitrogen against C-CN bond can be regarded as significant.     

Synthesis of anacardic acids, 6-[8(Z),11(Z)-pentadecadienyl]salicylic acid and 6-[8(Z),11(Z),14-pentadecatrienyl]salicylic acid

11-Chloro-3-methoxy-2-undecenal was synthesized from 8-bromooctanol, and an annelation reaction with this aldehyde and ethyl acetoacetate proceeded to give the ethyl 6-(8-chlorooctyl)salicylate. Ethyl 6-(8-chlorooctyl)salicylate was converted to ethyl 6-(7-formylheptyl)-2-methoxybenzoate through the iodide after protection of the phenolic hydroxyl group. Finally, the Wittig reaction with the aldehyde and triphenylphosphonium iodides in the presence of BuLi gave the methoxybenzoates, and then treatments of these methoxybenzoates with BBr3 in CH2Cl2 and 10% NaOH in ethanol gave 6-18(Z),11(Z)-pentadecadienyllsalicylic acid (anacardic acid 3) and 6-[8(Z),11(Z),14-pentadecatrienyl]salicylic acid (anacardic acid 4) which were isolated from plants of the anacardiaceae.     

Applicability of 0.05 mol kg potassium hydrogen phthalate as reference value pH standard in water–organic solvent mixtures

The applicability of 0.05 mol kg⁻¹ potassium hydrogen phthalate (KHPh(S), S=the solvent under study) as reference value pH standard (RVS) was studied in water–organic solvent mixtures. Phthalic acid in various aqueous organic solvent mixtures was titrated potentiometrically with Bu₄NOH (MeOH), using a pH-ISFET and a glass electrode as pH-sensors, and the buffer capacity of the HPh⁻ solution was roughly estimated from the difference between the first and second half-neutralization potentials. The influence of potassium ion to the buffer capacity was also studied, titrating KHPh and Et₄NHPh with CF₃SO₃H and Bu₄NOH (MeOH) and comparing the titration curves. The KHPh solution loses its buffer capacity if the solvent mixture has an aprotic property. For aqueous mixtures of protophilic aprotic solvents (e.g. DMSO and DMF), it is unsuitable as RVS if the water content is less than ca. 40 (v/v)%. The necessity of selecting subsidiary pH standard(s) is suggested for the solvent systems in which KHPh is inapplicable.     

Synthesis, structure, electrochemistry, and spectroelectrochemistry of hypervalent phosphorus(V) octaethylporphyrins and theoretical analysis of the nature of the PO bond in P(OEP)(CH(2)CH(3))(O)

A variety of phosphorus(V) octaethylporphyrin derivatives of the type [P(OEP)(X)(Y)](+)Z(-) (OEP: octaethylporphyrin) (X = CH(3), CH(2)CH(3), C(6)H(5), F; Y = CH(3), CH(2)CH(3), OH, OCH(3), OCH(2)CH(3), On-Pr, Oi-Pr, Osec-Bu, NHBu, NEt(2), Cl, F, O(-); Z = ClO(4), PF(6)) were prepared. X-ray crystallographic analysis of eleven compounds reveals that the degree of ruffling of the porphyrin core becomes greater and the average P-N bond distance becomes shorter as the axial ligands become more electronegative. Therefore, the electronic effect of the axial substituents plays a major role in determining the degree of ruffling although the steric effect of the substituents plays some role. A comparison of the (1)H NMR chemical shifts for the series of [P(OEP)(CH(2)CH(3))(Y)](+)Z(-) complexes with those of the corresponding arsenic porphyrins, which possess a planar core, indicates a much smaller ring current effect of the porphyrin core in the severely ruffled phosphorus porphyrins. The electrochemistry, spectroelectrochemistry and ESR spectroscopy of the singly reduced compounds are also discussed. The OH protons of [P(OEP)(X)(OH)](+) are acidic enough to generate P(OEP)(X)(O) by treatment with aq dilute NaOH. X-ray analysis of P(OEP)(CH(2)CH(3))(O) reveals that the PO bond length is very short (1.475(7) A) and is comparable to that in triphenylphosphine oxide (1.483 A). The features of the quite unique hexacoordinate hypervalent compounds are investigated by density functional calculation of a model (Por)P(CH(2)CH(3))(O) and (Por)P(F)(O) (Por: unsubstituted porphyrin).