Organic–Inorganic Azafullerene‐Gold C59N‐Au Nanohybrid: Synthesis,Characterization, and Properties

Azafullerene (C₅₉N) was functionalized using a Mannich‐type reaction and then subsequently condensed with lipoic acid to yield dithiolane‐modified C₅₉N. In the following step, the extended dithiolane moiety from the C₅₉N core was utilized to decorate the azafullerene sphere with gold nanoparticles (Au NPs). The latter were initially stabilized with dodecanothiol (DT ? Au) and then integrated on azafullerene through a ligand exchange reaction with the dithiolane‐functionalized C₅₉N to produce the C₅₉N/DT ? Au nanohybrid. The nanohybrid was fully characterized by spectroscopy and microscopy, revealing the formation of spherical nanoparticles with a diameter in the range of 2–5 nm, as imaged by HR‐TEM. In the electronic absorption spectrum of C₅₉N/DT ? Au nanohybrid, the characteristic surface plasmon band (SPB) of Au NPs was observed, however, it was redshifted compared with that of DT ? Au. The redshift of the SPB is indicative of closer interparticle proximity of Au NPs, in accordance with the formation of aggregated NPs as observed by TEM, in C₅₉N/DT ? Au nanohybrid. Excited‐state interactions in C₅₉N/DT ? Au were probed by photoluminescence assays. It was found that the weak emission of C₅₉N at 819 nm was blueshifted by 14 nm in C₅₉N/DT ? Au, but was stronger in intensity, thus suggesting energy transfer to C₅₉N, within the organic–inorganic C₅₉N/DT ? Au nanohybrid. Finally, with the aid of pump–probe measurements and transient absorption spectroscopy, the formation of the singlet excited state of C₅₉N was identified.     

Size‐Selective Complexation and Extraction of Endohedral Metallofullerenes with Cycloparaphenylene

A new strategy for the non‐chromatographic extraction of metallofullerenes from solutions of arc‐processed raw soot is based on the size‐selective complexation with cycloparaphenylene (CPP). [11]CPP has a high affinity for M_x@C₈₂ (x=1, 2); for example, Gd@C₈₂ can be selectively extracted from a fullerene mixture by the addition of [11]CPP. This approach should open new opportunities in metallofullerene chemistry, including for the bulk extraction of metallofullerenes.     

Iridium‐Catalyzed Enantioselective CH Alkylation of Ferrocenes with Alkenes Using Chiral Diene Ligands

The first catalytic and enantioselective C? H alkylation of ferrocene derivatives with various alkenes was achieved. A cationic iridium complex, having a chiral diene ligand, and an isoquinolyl moiety as a directing group are essential for regioselective and enantioselective C? H bond activation.     

Efficient and convenient heterogeneous palladium-catalyzed regioselective deuteration at the benzylic position

The Pd/C-catalyzed efficient and regioselective hydrogen-deuterium (H-D) exchange reaction on the benzylic site proceeded in D2O in the presence of a small amount of H2 gas. The use of the Pd/C-ethylenediamine complex [Pd/C(en)] as a catalyst instead of Pd/C led to the efficient deuterium incorporation into the benzylic site of O-benzyl protective groups without hydrogenolysis. These H-D exchange reactions provide a post synthetic and D(2)-gas-free deuterium-labeling method on a wide variety of benzylic sites using D2O as the deuterium source and heterogeneous Pd/C or Pd/C(en) as a reusable heterogeneous palladium catalyst under mild and neutral conditions.     

Sequence-specific alkylation by Y-shaped and tandem hairpin pyrrole-imidazole polyamides

To extend the target DNA sequence length of the hairpin pyrrole-imidazole (Py-Im) polyamide 1, we designed and synthesized Y-shaped and tandem hairpin Py-Im polyamides 2 and 3, which possess 1-(chloromethyl)-5-hydroxy-1,2-dihydro-3H-benz[e]indole (seco-CBI) as DNA-alkylating moieties. High-resolution denaturing polyacrylamide gel electrophoresis by using 5'-Texas-Red-labeled 465 base pair (bp) DNA fragments revealed that conjugates 2 and 3 alkylated the adenine of the target DNA sequences at nanomolar concentrations. Conjugate 2 alkylated adenine N3 at the 3' end of two 8 bp match sequences, 5'-AATAACCA-3' (site A) and 5'-AAATTCCA-3' (site C), while conjugate 3 recognized one 10 bp match sequence, 5'-AGAATAACCA-3' (site A) in the 465 bp DNA fragments. These results demonstrate that seco-CBI conjugates of Y-shaped and tandem hairpin polyamides have extended their target alkylation sequences.     

Rh-catalyzed intermolecular and enantioselective [4 + 2] cycloaddition of 1,3-dienes with dimethyl acetylenedicarboxylate

A Rh-BINAP complex catalyzed an intermolecular and enantioselective [4 + 2] cycloaddition of 1-monosubstituted, 1,1- or 1,2-disubstituted buta-1,3-dienes with dimethyl acetylenedicarboxylate to give chiral cyclohexa-1,4-dienes.     

Enantioselective syntheses of various chiral multicyclic compounds with quaternary carbon stereocenters by catalytic intramolecular cycloaddition

The intramolecular cycloaddition of 1,n-diene-ynes (n = 4-6), where alkyne and alkene moieties are connected by a 1,1-disubstituted alkene, was examined using a chiral rhodium catalyst, and various types of cycloadducts with quaternary carbon stereocenter(s) were obtained in high to excellent enantiomeric excess. In the case of 1,4-diene-ynes, tricyclic, bicyclic, and spirocyclic compounds were obtained depending upon the substituents at the 2-position of the 1,4-diene moiety and those at their alkyne termini. On the other hand, 1,5- and 1,6-diene-ynes gave tricyclic and bicyclic compounds, which included medium-sized ring systems. The mechanistic considerations for different reaction pathways and the synthetic transformation of tricyclic products into functionalized spirocyclic compounds are also described. The reaction of enediynes, where two alkyne moieties are connected by a 1,1-disubstituted alkene, was also examined, and sterically strained tricyclic compounds with two carbon stereocenters were obtained.     

Precise Zn isotopic ratio measurements of human red blood cell and hair samples by multiple collector-ICP-mass spectrometry.

Precise 66Zn/64Zn and 68Zn/64Zn isotopic ratios of biochemical samples have been measured using multiple collector-ICP-mass spectrometry (MC-ICPMS). In order to eliminate the mass spectrometric interferences on Zn isotopes (e.g., 64Ni+ and 136Ba2+), we chemically purified the analyte using an ion chromatographic technique. The resulting precisions of the 66Zn/64Zn and 68Zn/64Zn ratio measurements were 0.05/1000 and 0.10/1000 (2SD), respectively, which were enough to detect the isotopic variation of Zn in nature. Red blood cell (RBC) samples were collected from five volunteers (four males and one female), including a series of 12 RBC samples from one person through monthly-based sampling over a year. These were analyzed to test possible seasonal changes and variations in 66Zn/64Zn and 68Zn/64Zn ratios among the individuals. The 66Zn/64Zn and 68Zn/64Zn ratios for a series of 12 RBC samples collected over a year were 0.43/1000 and 0.83/1000 higher than the values of highly purified Zn metal (JMC Zn), and no seasonal change could be found. The 66Zn/64Zn and 68Zn/64Zn ratios for RBC samples collected from five volunteers did not vary significantly. In order to investigate Zn isotopic heterogeneity in a human body, Zn isotopic ratios of a hair sample collected from one of the volunteers was also analyzed. The 66Zn/64Zn and 68Zn/64Zn ratios for the hair sample were 0.59/1000 and 1.14/1000 lower than the mean value of RBC samples. This result demonstrates that detectable isotopic fractionation occurs in the human body. The data obtained here suggest that the isotopic ratios of trace metals could provide new information about transportation of metal elements in vivo.     

Short communication: An alternative and effective catalyst in the stereo‐specific reaction of Z‐1‐aryl‐1‐stannyl‐2‐silylethenes with allyl bromide

The Pd(dba)₂‐catalyzed reaction of Z‐1‐aryl‐1‐(tributylstannyl)‐2‐(trimethylsilyl)ethenes with allyl bromide in the presence of copper(I) iodide is reported for the first time. The reaction in the presence of 0.5 mol% Pd(dba)₂ and 8 mol% CuI in dimethylformamide takes place at room temperature to give E‐2‐aryl‐1‐(trimethylsilyl)penta‐1,4‐dienes exclusively in isolated yields of 62–99%. A putative reaction mechanism is proposed. Copyright © 2005 John Wiley & Sons, Ltd.