Unusual endoperoxide isomerizations: a convenient entry into 2-vinyl-2-cyclopentenones from saturated fulvene endoperoxides

An unusual peroxide base-promoted isomerization is uncovered. Saturated endoperoxides derived from fulvenes give rise to 2-vinyl-2-cyclopentenones upon treatment with DBU in CH₂Cl₂ in a one-pot reaction. This methodology is applied to a convenient synthesis of dihydrojasmone. Moreover, functional groups placed on the side chain at C-6 participate in the base-catalyzed isomerizations via conjugate attack at the enone moiety to give 2-cyclopentenones carrying oxygen heterocycles at C-2.     

Crystal structures and physical chemical properties of nedocromil zinc heptahydrate and nedocromil magnesium pentahydrate

The crystal structure of one of the hydrated forms of nedocromil zinc, the heptahydrate, and that of one of the hydrated forms of nedocromil magnesium, the pentahydrate, have been determined. Crystal data: zinc salt,a=11.769(3),b=7.000(2),c=14.022(4); Å; =105.35(2)°; monoclinic, space groupP2₁,Z=2;magnesium salt,a=7.460(1),b=10.233(2),c=13.934(2) Å, =86.54(1)°, =79.74(1)°, =77.25(1)°; triclinic, space groupP,Z=2. The major differences between the crystal structures are the environment and bonding of the cations. The zinc cation is linked directly to the carbonyl oxygen of the pyridone ring and to five water molecules in an octahedral coordination. The magnesium cation is linked directly to two different carboxyl oxygens, one in asyn orientation and the other in ananti orientation in different asymmetric units and to four water molecules in an octahedral coordination. Thermal analytical methods show that the zinc salt hydrate undergoes thermal dehydration at lower temperatures than the magnesium salt hydrate. This behavior may be related to the presence of continuous water channels in the zinc salt hydrate and to their absence in the magnesium salt hydrate. For each salt hydrate 1 mole of water is lost at a higher temperature than the other waters.     

Two birds with one metallic stone: single-pot catalysis of fundamentally different transformations

Advances in metal catalysis have revolutionized organic synthesis, with the scope of metal-catalyzed reactions now covering nearly all areas of carbon-carbon, carbon-hydrogen, and carbon-heteroatom bond formation. For years, the goal was to develop catalysts that were highly selective for a single transformation. However, a promising current area of research is the use of a single catalyst to mediate more than one transformation in a selective manner. Whereas much early work was focused on using a catalyst for several similar transformations, recent investigations have shown that it is also possible to employ a single catalyst for several very different transformations in a single reaction sequence. This Minireview focuses on methods in which the mechanisms of the transformations are fundamentally very different.     

Crystal structures and hydrogen bond analysis of three arenesulfonate salts ofl-alanine,glycine, andl-serine

Single crystal X-ray structures are presented for three amino acid arenesulfonate salts:l-alanine 2,4-dinitrobenzenesulfonate hydrate (1), 21 glycine 1,5-naphthalene-disulfonate dihydrate (2), andl-serine 4-hydroxybenzenesulfonate (3). Hydrogen bond patterns of each salt are analyzed systematically by using hydrogen bond graph set notation. First-, second-, and selected third-level graph set motifs of the three salts are presented and discussed. Hydrogen-bonded diad, chain, ring, ribbon, and two-dimensional sheet patterns are identified in these structures. Even though the three salts contain apparently similar types of hydrogen-bonding interactions, their graph sets are quite different.Deceased June 10, 1992.     

Ultrathin Antifouling Coatings with Stable Surface Zwitterionic Functionality by Initiated Chemical Vapor Deposition (iCVD)

Antifouling thin films of poly[N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl)-co-2-(dimethylamino)ethyl methacrylate-co-ethylene glycol dimethacrylate] (PDDE) were synthesized via a substrate-independent and all-dry-initiated chemical vapor deposition (iCVD) technique followed by a diffusion-limited vapor-phase reaction with 1,3-propane sultone. Coated surfaces exhibited very low absorption of various foulants including bovine serum albumin (BSA), humic acid (HA), and sodium alginate (SA), as measured with the quartz crystal microbalance with dissipation monitoring (QCM-D). The fouling by humic acid was dependent on the presence of divalent cations such as Ca(2+). Both depth profiling and angle-resolved X-ray photoelectron spectroscopy (XPS) measurements indicated that the zwitterionic groups were highly concentrated in the top ～3 nm of the film. The contact angle measurements revealed a limited degree of surface chain reorganization upon contacting water. The dynamic contact angles remained unchanged after 100 days of storage in air, indicating the stability of the interface. The coating was substrate-independent, and the film was conformal on surface nanostructures including trenches, reverse osmosis membranes, and electrospun nanofiber mats.     

Initiated chemical vapor deposition of poly(1H,1H,2H,2H-perfluorodecyl acrylate) thin films

A solvent-free initiated chemical vapor deposition (iCVD) process was used to create low surface energy poly(1H,1H,2H,2H-perfluorodecyl acrylate) (PPFDA) thin films at deposition rates as high as 375 nm/min. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy showed full retention of the fluorine moieties, and no measurable cross-linking was detected. Additionally, the FTIR studies support the hypothesis that film deposition results from vinyl polymerization. For all iCVD PPFDA films, the static contact angle was found to be 120.8 +/- 1.2 degrees. The roughness of the films was found to be between 14.9 and 19.8 nm RMS, and the refractive index of the films was found to be between 1.36 and 1.37. The deposition rate was studied as a function of the substrate temperature and the partial pressure of the monomer. It was found that the deposition rate increases with decreasing substrate temperature and increasing monomer partial pressure. It was also found that the molecular weight increases with decreasing substrate temperature and increases with increasing monomer partial pressure. The highest molecular weight measured was 177 300 with a polydispersity of 2.27. Quartz crystal microbalance (QCM) measurements showed that these effects correlated with an increased monomer concentration at the surface. The deposition rate data and the QCM data were quantitatively analyzed to find the rate constants of the process using a previously published model for the iCVD process involving nonfluorinated monomers. The determined values of the rate constants of the surface polymerization were found to be similar to the rate constants measured in liquid-phase free radical polymerization. The kinetic data found in this paper can now be used to study iCVD deposition onto substrates with more complex geometries.