Advances in the Chemistry of the Tropylium Ion

Abstract

The multi-electrode current source (MECS) interstitial hyperthermia system, which is used for treatment of cancer, employs segmented electrodes inserted in plastic tubes implanted in the treatment volume. The mean power deposition of the individual electrodes is controlled by varying the duty cycle of the RF signal applied to the electrodes, using thermocouples inside the electrodes for thermometry.A non-zero loss angle results in self-heating of the catheter. The thermal influence of selfheating was investigated and an analysis of the measurement of temperatures inside the catheter during and after heating is presented. Analytical models and a high-resolution numerical model were used for the calculation of steady state and transient distributions, respectively. The model results are compared with experimental data obtained in a muscle equivalent phantom.Results indicate that there is no difference between temperature inside and outside the catheter when using lossless catheter materials (e.g. PE and PTFE). Self-heating in the catheter wall has an adverse effect on the uniformity of the stationary temperature distribution and the reliability of temperature measurement with internal thermometry. These problems remain within acceptable limits for mildly lossy materials; the difference between the temperature inside and outside is only 6% when using low-loss Nylon.Analysis of the thermal decay after power-off shows that low-loss materials allow more time to obtain an accurate estimate of the tissue temperature at the catheter wall during power-on. This effect is enhanced by the presence of minute air layers in the applicator.Distortion of temperature gradients along the catheter was also investigated. Key factors are the thermal conduction across the catheter wall, and especially the presence of minute layers of air between consecutive layers of the probe. The distortion extends less than two millimetres, which is acceptable.The simulation results are compatible with measurements in phantoms and show that, if the proper choice of materials is made, the MECS applicator answers our expectations and that the temperature measurement inside the catheter can be used for direct feedback treatment control.

Fluxionality in the Tropolone Hinokitiol Chelate

“…The excited states responsible for this fluxionality can be tropolone-based as well as those delocalized over the M−L ensemble. Tropolones have a rich chemistry frequently involving tropelium cations, 32 as well as benzenoid intermediates. 15 The latter are the reverse of the carbene/ beneznoid addition/rearrangement leading to many tropolones, 33 as well as the reverse of the formal oxidation/ring expansion found in the catechol interdiol oxygenases.…”

Structure of HIV-1 Reverse Transcriptase with the Inhibitor β-Thujaplicinol Bound at the RNase H Active Site

“…A tropylium ion is a seven-membered aromatic ring, containing three conjugated double bonds and an overall +1 charge (for reviews, see refs [18-20], Figure 6 Inset). If one of the carbon atoms is changed to a carbonyl, the ring is called a tropolone, and the ring retains some aromatic character[21].…”

Seven-membered conjugated carbo- and heterocyclic compounds and their homoconjugated analogs and metal complexes. Synthesis, biosynthesis, structure, and reactivity

“…This is a general method for the synthesis of compounds of the type 143 and works well also with diamines in the place of hydrazine.114 Formally related to aminotroponeimines are also 1,3diazaazulenes (144) and 1,3-diazaazulenium Ions, such as 145.114 General methods for the synthesis of 1,3-diazaazulenes will be discussed in section V.A.2. The parent compound, heptafulvene (147), has been obtained by several methods such as Hofmann elimination at room temperature in vacuo from the ammonium (113) G. Sunagawa and N. Soma, Japan Patent 12674 (1962); Chem. Abstr., 60, 4064h (1964). (114) W. R. Erasen, .…”

“…Chem. Soc., 83, 3125 (1961) Heptafulvene is also formed, together with benzene, acetylene, and cyclooctatetraene, in the thermal or photochemical decomposition of cycloheptatrienyldiazomethane.120 A reasonable mechanism for this reaction is decomposition of the diazoalkane to give the carbene 150 which then rearranges to 147.120 H 150 Heptafulvene is a very labile compound which easily polymerizes, even at -80°, in concentrated solutions.117 Recently, however, the above-mentioned pyrolysis of the mixture of acetoxymethylcycloheptatrienes (Scheme XVII), with collection of the pyrolyzates at -70°followed by purifications at low temperature, allowed the preparation of deep-red crystalline 147 which is stable at -70°b ut polymerizes in a few minutes at 20°.,,9b At moderately low temperatures it was possible to obtain nmr and ir spectra11913 (section IV.B.3). Less labile, or even stable, heptafulvenes were obtained by either replacing the methylene hydrogens with strongly electron-attracting groups or Inserting the methylene carbon into a conjugated chain or cycle as shown by subsequent examples.…”