A DFT Study on the Conversion of Aryl Iodides to Alkyl Iodides: Reductive Elimination of R−I from Alkylpalladium Iodide Complexes with Accessible β‐Hydrogens

DFT calculations have been performed on the palladium‐catalyzed carboiodination reaction. The reaction involves oxidative addition, alkyne insertion, C?N bond cleavage, and reductive elimination. For the alkylpalladium iodide intermediate, LiOtBu stabilizes the intermediate in non‐polar solvents, thus promoting reductive elimination and preventing β‐hydride elimination. The C?N bond cleavage process was explored and the computations show that PPh₃ is not bound to the Pd center during this step. Experimentally, it was demonstrated that LiOtBu is not necessary for the oxidative addition, alkyne insertion, or C?N bond cleavage steps, lending support to the conclusions from the DFT calculations. The turnover‐limiting steps were found to be C?N bond cleavage and reductive elimination, whereas oxidative addition, alkyne insertion, and formation of the indole ring provide the driving force for the reaction.     

Coordination‐Driven Self‐Assembly and Anticancer Potency Studies of Ruthenium–Cobalt‐Based Heterometallic Rectangles

Three new cobalt–ruthenium heterometallic molecular rectangles, 1 – 3 , were synthesized through the coordination‐driven self‐assembly of a new cobalt sandwich donor, (η⁵‐Cp)Co[C₄‐trans‐Ph₂(4‐Py)₂] (L ; Cp: cyclopentyl; Py: pyridine), and one of three dinuclear precursors, [(p‐cymene)₂Ru₂(OO∩OO)₂Cl₂] [OO∩OO: oxalato ( A₁ ), 5,8‐dioxido‐1,4‐naphthoquinone ( A₂ ), or 6,11‐dioxido‐5,12‐naphthacenedione ( A₃ )]. All of the self‐assembled architectures were isolated in very good yield (92–94 %) and were fully characterized by spectroscopic analysis; the molecular structures of 2 and 3 were determined by single‐crystal X‐ray diffraction analysis. The anticancer activities of bimetallic rectangles 1 – 3 were evaluated with a 3‐[4,5‐dimethylthiazol‐2‐yl]‐2,5‐diphenyltetrazolium bromide (MTT) assay, an autophagy assay, and Western blotting. Rectangles 1 – 3 showed higher cytotoxicity than doxorubicin in AGS human gastric carcinoma cells. In addition, the autophagic activities and apoptotic cell death ratios were increased in AGS cells by treatment with 1 – 3 ; the rectangles induced autophagosome formation by promoting LC3‐I to LC3‐II conversion and apoptotic cell death by increasing caspase‐3/7 activity. Our results suggest that rectangles 1 – 3 induce gastric cancer cell death by modulating autophagy and apoptosis and that they have potential use as agents for the treatment of human gastric cancer.     

Nonisothermal crystallization kinetics of biodegradable poly(butylene succinate‐co‐propylene succinate)s

Poly(butylene succinate) (PBSu) and two poly(butylene succinate‐co‐propylene succinate)s were synthesized via the direct polycondensation reaction. The copolyesters were characterized as having 7.0.and 11.5 mol % propylene succinate (PS) units, respectively, by ¹H NMR. A differential scanning calorimeter (DSC) and a polarized light microscope (PLM) adopted to study the nonisothermal crystallization of these polyesters at a cooling rate of 1, 2, 3, 5, 6, and 10 °C/min. Morphology and the isothermal growth rates of spherulites under PLM experiments were monitored and obtained by curve‐fitting. These continuous rate data were analyzed with the Lauritzen?Hoffman equation. A transition of regime II → III was found at 95.6, 84.4, and 77.3 °C for PBSu, PBPSu 95/5, and PBPSu 90/10, respectively. DSC exothermic curves show that all of the nonisothermal crystallization occurred in regime III. DSC data were analyzed using modified Avrami, Ozawa, Mo, Friedman, and Vyazovkin equations. All the results of PLM and DSC measurements indicate that incorporation of minor PS units into PBSu markedly inhibits the crystallization of the resulting polymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1299–1308, 2010     

A non‐natural dinucleotide containing an isomeric l‐related deoxy­nucleoside: dinucleotide inhibitors of anti‐HIV integrase activity

The first X‐ray crystal structure of a non‐natural dinucleotide, 5′‐O‐phosphoryl‐1′‐deoxy‐2′‐isoadenylyl‐(3′ → 5′)‐cytidine 6.5‐hydrate (pIsodApC), C₁₉H₂₆N₈O₁₃P₂·6.5H₂O, belonging to a family of dinucleotides that contain an isomeric nucleoside component, is described. A complex system of hydrogen bonds between water mol­ecules and various sites on the dinucleotide was found. All H atoms were located from electron‐density difference maps, which allowed identification of protonation sites. Compounds of this family have been found to bind at the active site of HIV integrase and to be inhibitors of this key viral enzyme. These dinucleotides are completely resistant to cleavage by exonucleases; an abnormal dihedral angle twist in an inter­nucleotide phosphate bond revealed in the X‐ray crystal structure may be contributing to this unusual stability towards nucleases.     

A Novel Method to Convert Ketones and Aldehydes to the Corresponding Alcohols

A novel method of converting aldehydes and ketones to the corresponding alcohols based on selective indirective electroreduction was found, in which EtOH was used as a support electrolyte and Al(OC₂H₅)₃ as intermedia that was produced on spot reduction by electrolysis. The reaction took place in a cell with two Al electrodes.     

Preparation,characterization, and properties of fluorene‐containing benzoxazine and its corresponding cross‐linked polymer

A benzoxazine compound (FDP‐FBz), which possesses a fluorene group and two terminal furan groups, and its corresponding cross‐linked polymer (CR‐FDP‐FBz) have been prepared using 4,4′‐(9‐fluorenylidene)diphenol (FDP), furfurylamine, and formaldehyde as precursors. The chemical structure of FDP‐FBz has been characterized with Fourier‐transform infrared and ¹H nuclear magnetic resonance spectroscopies. FDP‐FBz displays a melting point at about 173 °C and a processing window of 52 °C as well as good solubility in common organic solvents. As a result, FDP‐FBz can be fabricated in both molten and solution processes. Under an excitation at 365 nm, FDP‐FBz exhibits a photoluminescent (PL) emission at about 445 nm. The PL intensity of FDP‐FBz is as high as sixfolds of the intensity recorded with FDP. CR‐FDP‐FBz displays a glass transition temperature of 215 °C, a high storage modulus of 3.1 GPa, a 10% weight loss at 384 °C, and a high char yield of 56 wt % (900 °C, in nitrogen). Moreover, CR‐FDP‐FBz has a high refractive index of about 1.65 as a result of incorporating fluorene groups to its structure. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4020–4026, 2010