Alternative methods for the MnO2 oxidation of codeine methyl ether to thebaine utilizing ionic liquids

The MnO2 oxidation of codeine methyl ether, CME, to thebaine has been accomplished via the use of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, bmimBF4. The ionic liquid has been used to remove or extract excess MnO2 and associated impurities from the reaction mixture to afford thebaine in 36 to >95% yield. © 2001 Elsevier Science Ltd. All rights reserved.

Manganese dioxide allylic and benzylic oxidation reactions in ionic liquids

Ionic liquids 1-butyl-3-methylimidazolium tetrafluoroborate [bmIm][BF₄] and 1-butyl-3-methylimidazolium hexafluorophosphate [bmIm][PF₆] were evaluated as reaction media for allylic and benzylic oxidation reactions using manganese dioxide. The use of ionic liquids as an extractant in the reaction work-up was also investigated. Procedures for recycling of the [bmIm][PF₆] ionic liquids used in these MnO₂ oxidation reactions were also developed.

Bone formation following implantation of titanium sponge rods into humeral osteotomies in dogs : a histological and histometrical study

Background: Titanium (Ti) is widely proven to enhance bone contact and growth on its surface. It is expected that bone defects could benefit from Ti to promote healing and to increase strength of the implanted area.

Purpose: The present study aimed at comparing the potential of porous Ti sponge rods with synthetic hydroxyapatite (HA) for the healing of bone defects in a canine model.

Material and Methods: Six mongrel dogs were submitted to three trephined osteotomies of 6.0 × 4.0 mm in one humerus and after 2 months another three osteotomies were performed in the contralateral humerus. A total of 36 defects were randomly filled either with Ti foam, particulate HA, or coagulum (control). The six animals were killed 4 months after the first surgery for histological and histometrical analysis.

Results: The Ti-foam surface was frequently found in intimate contact with new bone especially at the defect walls. Control sites showed higher amounts of newly formed bone at 2 months – Ti (p = 0.000) and HA (p = 0.009) – and 4 months when compared with Ti (p = 0.001). Differently from HA, the Ti foam was densely distributed across the defect area which rendered less space for bone growth in the latter's sites. The use of Ti foams or HA resulted in similar amounts of bone formation in both time intervals. Nevertheless, the presence of a Ti-foam rod preserved defect's marginal bone height as compared with control groups. Also, the Ti-foam group showed a more mature bone pattern at 4 months than HA sites.

Conclusion: The Ti foam exhibited good biocompatibility, and its application resulted in improved maintenance of bone height compared with control sites. The Ti foam in a rod design exhibited bone ingrowth properties suitable for further exploration in other experimental situations.

Tunable wettability of polyimide films based on electrostatic self-assembly of ionic liquids

We have demonstrated that the surface wettability of negatively charged polyimide films could be turned by electrostatic self-assembly of ionic liquids. The water contact angles of the polyimide films varied in the range 27-80 degrees for 13 different ionic liquids based on imidazolium and ammonium salts. The surface morphology of the resulting surfaces was characterized using atomic force microscopy. The results revealed that the assembly of longer-substituent cations was characterized by the formation of spherical nanoparticles that were formed due to sequent aggregation of cations on those electrostatically assembled ones via hydrophobic interaction. In this case, the counteranions are present in the assembled layers and the wettability is accordingly affected. Whereas for shorter-substituent cations, no aggregates were formed due to the less hydrophobic interaction than the electrostatic repulsive interaction between the cations, and the counteranions were absent from the assembled layers. This method can also be utilized to quantify the hydrophobicity of various ionic liquids.

Bronsted acidic ionic liquids derived from alkylamines as catalysts and mediums for Fischer esterification : study of structure–activity relationship

Esterification of acetic acid with 1-octanol was studied using a series of alkylammonium salts as Brønsted acidic ionic liquids. The following
ionic liquids were prepared and used as catalysts and mediums in the esterification reaction; [Et₃NH][HSO₄], [Et₃NH][H₂PO₄], [Et₃NH][BF₄],
[Et₃NH][p-CH₃C₆H₄SO₃], [Et₂(PhCH₂)NH][HSO₄], [n-Bu₃NH][HSO₄], [n-Oct₃NH][HSO₄], [Et₂NH₂][HSO₄], [Et₂NH₂][H₂PO₄], [Et₂NH₂]
[BF₄], [i-Pr₂NH₂][HSO₄], [EtNH₃][HSO₄], [EtNH₃][H₂PO₄], and [EtNH₃][BF₄]. Higher acidity of the anion in the ionic liquid resulted in high yield of the ester. Yield of the ester decreased with increase in the size of the cation. There was no phase separation in the reactions where size of anion and/or cation was bigger

Dispersion of boron nitride nanotubes in aqueous solution with the help of ionic surfactants

We report that ammonium oleate surfactants can help the dispersion of multiwalled boron nitride nanotubes (BNNTs) in water to form a BNNT solution stable for several months, which was due to the non-covalent functionalization of nanotube surfaces. Fourier Transform Infrared Spectroscopy (FTIR) and Photoluminescence (PL) analysis with synchrotron radiation source revealed that this BNNT aqueous solution preserves the intrinsic optical properties of BNNTs. © 2009 Elsevier Ltd. All rights reserved.