Reactivity of pyrrole pigments. part 6: Electrochemical reduction of some s(1h)-pyrromethenones and 5-arylmethylene-3,4-dimethyl-3-pyrrolin-2-ones

The electrochemical reduction of some 5(1H)-pyrromethenones and 5-arylmethylene-3-pyrrolin-2-ones in imethylformamide (DMF) has been studied by polarography and by identification of their electrochemical reduction products. The reduction processes observed depend on the presence on the type of supporting electrolyte. LiClO₄ or tetraethyl ammonium perchlorate (TEAP) and, When TEAP is used, they also depend on the presence of Water. Polarographic curves show two monoelectronic diffusion Waves in anhydrous DMF both with LiCIO₄ and with TEAP. The reaction products from (Z)-3,4-dimethyl-5-[(4-methylphenyl)methylene]-3-pyrrolin-2-one and from (Z)-2-[(3,4-dimethyl-5-oxo-3-pyrrolin-2-yl)-methylene]-1H-pyrrole for the electrolysis at controlled potentials and under different experimental conditions have been isolated and identified.In all cases a stereoselective reductive dimerization occurs but, at second wave potentials, the reduction compounds corresponding to the hydrogenation of the exocyclic double bond are also formed. The electrolysis yields can be optimized in order to make the process synthetically useful.     

Dehydrogenation with phenylseleninic anhydride in the total synthesis of ergot alkaloids

The standardised procedure for dehydrogenation of indolines into indoles with phenylseleninic anhydride $\text{1}$ was successfully applied to the final steps in the total synthesis of ergot alkaloids.     

Regioselective synthesis of azetidines or pyrrolidines by selenium-induced cyclization of secondary homoallylic amines

Azetidines or pyrrolidines can be regioselectively obtained by selenocyclization of homoallylic amines, according to the double bond substitution.     

Mass spectrometric characterization of tamoxifene metabolites in human urine utilizing different scan parameters on liquid chromatography/tandem mass spectrometry

Different liquid chromatographic/tandem mass spectrometric (LC/MS/MS) scanning techniques were considered for the characterization of tamoxifene metabolites in human urine for anti‐doping purpose. Five different LC/MS/MS scanning methods based on precursor ion scan (precursor ion scan of m/z 166, 152 and 129) and neutral loss scan (neutral loss of 72 Da and 58 Da) in positive ion mode were assessed to recognize common ions or common losses of tamoxifene metabolites. The applicability of these methods was checked first by infusion and then by the injection of solution of a mixture of reference standards of four tamoxifene metabolites available in our laboratory. The data obtained by the analyses of the mixture of the reference standards showed that the five methods used exhibited satisfactory results for all tamoxifene metabolites considered at a concentration level of 100 ng/mL, whereas the analysis of blank urine samples spiked with the same tamoxifene metabolites at the same concentration showed that the neutral loss scan of 58 Da lacked sufficient specificity and sensitivity. The limit of detection in urine of the compounds studied was in the concentration range 10–100 ng/mL, depending on the compound structure and on the selected product ion. The suitability of these approaches was checked by the analysis of urine samples collected after the administration of a single dose of 20 mg of tamoxifene. Six metabolites were detected: 4‐hydroxytamoxifene, 3,4‐dihydroxytamoxifene, 3‐hydroxy‐4‐methoxytamoxifene, N‐demethyl‐4‐hydroxytamoxifene, tamoxifene‐N‐oxide and N‐demethyl‐3‐hydroxy‐4‐methoxytamoxifene, which is in conformity to our previous work using a time‐of‐flight (TOF) mass spectrometer in full scan acquisition mode. Copyright © 2010 John Wiley & Sons, Ltd.     

Cytotoxic Evaluation of Pungencine: A New Tropane Alkaloid from the Roots of Erythroxylum pungens O. E. Schulz

A new tropane alkaloid as well as a new substitution group, (3‐endo,8‐anti)‐8‐methyl‐8‐azabicyclo[3.2.1]oct‐3‐yl 4‐hydroxy‐3,5‐dimethoxybenzoate, called pungencine ( 1 ), was isolated from the roots of Erythroxylum pungens O. E. Schulz . The structure was elucidated by spectral analyses, including ¹H‐ and ¹³C‐NMR and 2D‐NMR techniques (¹H,¹H‐COSY, NOESY, DEPT, HMQC, and HMBC) and HR‐ESI‐MS. Furthermore, compound 1 was tested for cytotoxicity against several cell lines (Jurkat, HL‐60, U937, K562, KG‐1, and U266) and was determined not to inhibit cell viability at 10 μM .     

Self‐Relay Gold(I)‐Catalyzed Pictet–Spengler/Cyclization Cascade Reaction for the Rapid Elaboration of Pentacyclic Indole Derivatives

Gold‐catalyzed cascade reactions allow the rapid elaboration of pentacyclic indolo[2,3‐a]quinolizidines from N‐allyl tryptamines and ortho‐alkynylarylaldehydes. The tandem process combines a gold‐catalyzed Pictet‐Spengler reaction and a cyclization occurring concomitantly with an allyl transfer from the nitrogen atom to the stilbene function. Various substituted allyls were successfully transferred, furnishing the products in yields typically ranging from 60–98 % in high diastereoselectivity. Tryptamines bearing a butenol chain undergo an additional cyclization to chiral hemiaminals in high diastereoselectivities.     

Stereoselective Synthesis of Chiral Polycyclic Indolic Architectures through Pd0‐Catalyzed Tandem Deprotection/Cyclization of Tetrahydro‐β‐carbolines on Allenes

Enantioenriched N‐allyl tetrahydro‐β‐carbolines were prepared by chiral phosphoric acid‐catalyzed Pictet–Spengler reactions. The compounds undergo Pd⁰‐catalyzed cyclizations through a tandem deprotection/cyclization process. The regioselectivity of the attack is controlled by the chain length and by the substitution pattern of the allene function. Products resulting from 5‐exo‐ or 6‐exo‐attack were obtained with diastereoisomeric ratio up to 95:5. Azepinopyrrido[3,4‐b]indoles were obtained by 7‐endo‐cyclizations.     

Cage‐like Copper(II) Silsesquioxanes: Transmetalation Reactions and Structural,Quantum Chemical,and Catalytic Studies

The transmetalation of bimetallic copper–sodium silsesquioxane cages, namely, [(PhSiO_1.5)₁₀(CuO)₂(NaO_0.5)₂] (“Cooling Tower”; 1 ), [(PhSiO_1.5)₁₂(CuO)₄(NaO_0.5)₄] (“Globule”; 2 ), and [(PhSiO_1.5)₆(CuO)₄(NaO_0.5)₄(PhSiO_1.5)₆] (“Sandwich”; 3 ), resulted in the generation of three types of hexanuclear cylinder‐like copper silsesqui‐ oxanes, [(PhSiO_1.5)₁₂(CuO)₆(C₄H₉OH)₂(C₂H₅OH)₆] ( 4 ), [(PhSiO_1.5)₁₂(CuO)₆(C₄H₈O₂)₄(PhCN)₂(MeOH)₄] ( 5 ), and [(PhSiO_1.5)₁₂(CuO)₆(NaCl)(C₄H₈O₂)₁₂(H₂O)₂] ( 6 ). The products show a prominent “solvating system–structure” dependency, as determined by X‐ray diffraction. Topological analysis of cages 1 – 6 was also performed. In addition, DFT theory was used to examine the structures of the Cooling Tower and Cylinder compounds, as well as the spin density distributions. Compounds 1 , 2 , and 5 were applied as catalysts for the direct oxidation of alcohols and amines into the corresponding amides. Compound 6 is an excellent catalyst in the oxidation reactions of benzene and alcohols.     

Temperature‐ and Voltage‐Induced Ligand Rearrangement of a Dynamic Electroluminescent Metallopolymer

A dynamic‐covalent metal‐containing polymer was synthesized by the condensation of linear diamine and dialdehyde subcomponents around copper(I) templates in the presence of bidentate phosphine ligands. In solution, the red polymers undergo a sol–gel transition upon heating to form a yellow gel, a process that can be either reversible or irreversible depending on the solvent used. When fabricated into a light‐emitting electrochemical cell (LEC), the polymer emits infrared light at low voltage. As the voltage is increased, a blue shift in the emission wavelength is observed until yellow light is emitted, a process which is gradually reversed over time upon lowering the voltage. The mechanism underlying these apparently disparate responses is deduced to be due to loss of the copper phosphine complex from the polymer.