An Efficient Method for the Synthesis of Acyl-diazenes Using NaNO_2/NaHSO_4·H_2O

Azo compounds are widely utilized as analytic reagents and dyes1, they can also be used in material of non-linear optics, material of optics information storing in laser disks, and dyes with oil solubility in photochromy in modern technology2. Recently, many noteworthy studies have shown that some azo compounds possess excellent optical memory and photoelectric properties3,4. For example, polymer scaffolds bearing azobenzene-potential are useful for optical information storage, azo-dye doped…     

Terpsichorean movements of pentaammineruthenium on pyrimidine and isocytosine ligands

Pentaammineruthenium moves on ambidentate nitrogen heterocycles by both rotation and linkage isomerization, which may affect the biological activity of potential ruthenium metallopharmaceuticals. The rapid rotation rates of [(NH3)5RuIII] coordinated to the exocyclic nitrogens of isocytosine (ICyt) and 6-methylisocytosine (6MeICyt) have been determined by 1H NMR. Since these rotamers can be stabilized by hydrogen bonding between the coordinated ammines and the N1 and N3 endocyclic nitrogens, rotamerization is under pH control. Spectrophotometrically (UV-vis) measured pKa values for the two endocyclic sites for the ICyt complex are 2.78 and 9.98, and for 6MeICyt are 3.06 and 10.21, which are probably weighted averages for ionization from N3 and N1, respectively. Activation parameters for the rotamerizations were determined by variable-temperature NMR at pKa1 < pH < pKa2 for the complexes with (ICyt-kappa N2)-, (6MeICyt kappa N2)-, and 2AmPym kappa N2. For [(6MeICyt kappa N2)(-)-(NH3)5RuIII]2+, delta H* = 1.6 kcal/mol, delta S* = -37 cal/mol K, and Ea = 2.2 kcal/mol. Due to strong RuIII-N pi-bonding, the activation enthalpies are approximately 10 kcal lower than the expected values for the free ligands. Rotameric structure is correlated with pKa values, pH-dependent reduction potentials, and 1H NMR parameters. Linkage isomers of [(2AmPym)(NH3)5Ru]n+ are reported in which RuII is coordinated to the endocyclic nitrogen (N1) and RuIII to the exocyclic nitrogen (N2). The rate constant for the kappa N2-->kappa N1 isomerization as part of an ECE mechanism is 3.9 s-1 at pH 3. The pH dependence of the acid-catalyzed hydrolysis of [(2AmPym kappa N1)(NH3)5Ru]2+ is determined.     

Carbene-catalyzed activation of cyclopropylcarbaldehydes for mannich reaction and δ-lactam formation: remote enantioselecitvity control and dynamic kinetic asymmetric transformation

An N-heterocyclic carbene(NHC)-catalyzed enantioselective Mannich reaction of the remote γ-carbon of cyclopropylcarbaldehydes is disclosed for the first time. Diastereo-and enantiomerically enriched multicyclic δ-lactam compound is afforded as the main product from 8 possible stereo-specific isomers through dynamic kinetic asymmetric transformation(DYKAT) processes. Multiple chiral functional molecules can be afforded from the lactam products through simple protocols with retentions of the optical purities.     

Structural and Bonding Properties of AlnC4-/0 (n=2-4) Clusters:Anion Photoelectron Spectroscopy and Theoretical Calculations

We measured the photoelectron spectra of AlnC4-(n=2-4) clusters by using size-selected anion photoelectron spectroscopy.The structures of AlnC4-/0 (n=2-4) clust...