Benzothiophenes structure

The literature on conductivity in poly(p-phenylene sulfide) is confused. According to Shacklette et al.74) heavy doping with AsF5 causes reduction of the polymer with the formation of fused benzothiophene structures which are responsible for conjugation. This would more properly place poly(p-phenylene sulfide) in the category of precursor polymers, discussed later. On the other hand, Friend and Giles 75) proposed an intrinsic conduction mechanism, based on optical measurements and Tsukamoto et al. 76) have presented XPS and 13C NMR measurements to support this view. 

Benzo[b]thiophene-2,3-quinone, 5-chloro-oxidation, 4, 824 Benzothiophenes, 4, 863-934 biological activity, 4, 911-913 intramolecular acylation, 4, 761 mass spectrometry, 4, 739 metabolism, 1, 242 phosphorescence, 4, 16 reactivity, 4, 741-861 spectroscopy, 4, 713-740 structure, 4, 713-740 substituents reactivity, 4, 796-839... 

Although desulfurization is a process, which has been in use in the oil industry for many years, renewed research has recently been started, aimed at improving the efficiency of the process. Envii onmental pressure and legislation to further reduce Sulfur levels in the various fuels has forced process development to place an increased emphasis on hydrodesulfurization (HDS). For a clear comprehension of the process kinetics involved in HDS, a detailed analyses of all the organosulfur compounds clarifying the desulfurization chemistry is a prerequisite. The reactivities of the Sulfur-containing structures present in middle distillates decrease sharply in the sequence thiols sulfides thiophenes benzothiophenes dibenzothio-phenes (32). However, in addition, within the various families the reactivities of the Substituted species are different. 

A cationic molybdenum sulfide cluster [Mo3S4(H20)9] " with incomplete cubane-type structure and a cationic nickel-molybdenum mixed sulfide cluster [Mo3NiS4Cl(H20)9p " with complete cubane-type structure were introduced into zeolites NaY, HUSY and KL by ion exchange. Stoichiometry of the ion exchange was well established by elemental analyses. The UV-visible spectra and EXAFS analysis data exhibited that the structure of the molybdenum cluster remained virtually intact after ion exchange. MoNi/NaY catalyst prepared using the molybdenum-nickel sulfide cluster was found to be active and selective for benzothiophene hydrodesulfurization. 

This paper describes the successful incorporation of molybdenum and molybdenum-nickel clusters into zeolites with 12-membered ring by aqueous ion exchange and application of the resulting materials to HDS reaction of benzothiophene. Stoichiometry of the ion exchange was examined by elemental analysis. UV-visible spectroscopy and EXAFS measurements were carried out to investigate the structure of molybdenum species loaded on zeolites. 

Table 5 shows HDS product distributions over several catalysts prepared by using the molybdenum-nickel cluster 2. Sulfur content in decane was adjusted to 5.0 wt% in these experiments. MoNi/NaY was found to be more active than MoNi/Al203. It is to be noted that during the high temperature pretreatment the original cluster structure would have been changed. However, the high activity of the MoNi/NaY catalyst for benzothiophene HDS is probably due to the formation of active sites derived from this particular mixed metal cluster. 

Fig. 2.2. Chemical structure of several SERMs in benzothiophene group...

Symmetrical and unsymmetrical thenoines, diketones, and chloro ketones 213-225 containing substituted thienyl, benzothiophene, and other moieties are versatile precursors of structures containing various heterocycles as bridges. Chloro ketones were used, for example, in the synthesis of photochromic thiazoles 226 (01IZV113) and tetrathiafulva-lenes 227 (99CL1071) (Scheme 65). 

The structure of a novel benzothiophene glycoside, echinothiophene 132, isolated from the roots of Echinops grijissii was elucidated by a combination of spectroscopic methods (MS and NMR) <990L197>. Interestingly, 132 undergoes a facile epimerization to 134, perhaps through enol intermediate 133. 

A reactivity study of the isomeric 2-vinylthieno[3,2-/ ][l]henzofuran 95 as well as of the structurally related 2-vinyl[l]thieno[3,2-/ ][l]benzothiophene 96 and 2-vinylthieno[3,2- ]thiophene 97 with dienophiles was performed by Svoboda and co-workers <2004TL2189>. Cycloaddition reactions were performed by heating 95-97 with dimethyl acetylenedicarboxylate (DMAD) to reflux in toluene under a nitrogen atmosphere. 

Benzothiophene-1,1-dioxide (VI) in benzene solution, is converted in sunlight into a stable photodimer (Vila or VHb), which is considered to contain a central cyclobutane structure.56 196 Even though the monomer cannot be isolated on thermal decomposition of the dimer, the latter in boiling ethyl phthalate decomposes, forming sulfur dioxide and... 

A and B. DE values were calculated from the W values given in Section IV, A for the Kekul6 structures of types 131 and 132. The data for benzothiophenes (Fig. 18) make it clear that Model Al yields DE... 

Recent work by Kvitko et a/.409 on thieno[2,3-c]pyrazoles 393 has shown that bromination and formylation (Vilsmeier reaction) take place at C-2, i.e., a to sulfur, though benzothiophene generally substitutes in the / -position.4090 These Russian workers argue that, for 393, a transition state such as 395 will be less unfavorable than the corresponding transition state 394 for benzothiophenes, since 394 has to adopt a quinonoid structure (see 90c and 282b, Section IV,A,1). 

The fluorescence excitation and emission spectra of the electrogenerated fused benzothiophene oligomers [poly(39) and poly(41)] show the existence of dramatic red shifts of the fluorescence maxima and important increases of the fluorescence intensity relative to the parent monomers. These results suggest the existence of extended electronic conjugation in the oligomer chains. Poly(39) and poly(41) showed a well-structured excitation band with maxima at about 335 nm and 395 nm, respectively. These excitation maxima are strongly red shifted by about 50 and 108 nm, respectively, against the 39 and 41 excitation spectra. The emission spectra are characterized by a relatively wide, poorly structured band, centered at 410 nm and 445 nm, respectively. These emission maxima also present dramatic red shifts relative to the emission spectra of the parent monomers. 

As complex as the desulfurization of thiophene might appear, projection of the kinetic picture to benzothiophene and dibenzothiophene, and to their derivatives, is even more complex. As has already been noted for bond energy data, kinetic data derived from model compounds cannot be expected to include contributions from the various steric effects that are a consequence of complex molecules containing three-dimensional structures. Indeed, such steric effects can lead to the requirement of additional catalyst and process parameters for sulfur removal (Isoda et al., 1996a, 1996b). 

Benzothiophene. There have been several reports on the aerobic co-metabolism of benzothiophene (42, 46, 47). Bohonos et al. (46) identifed some benzothiophene metabolites by GC-MS and the structures of these are shown in Figure 8. Although the only compounds found were oxidized on the thiophene ring, they could not exclude the possibility of oxidation of the benzene ring. Finnerty et al. (48) found that benzothiophene was transformed to unidentified water-soluble products by a dibenzothiophene-oxidizing bacterium. 

Thiophene complexes, containing a(S)-coordination bond, are represented by a high number of structures [8,13,205b,622,623]. Compound 321 [8] is an example of these complexes. (a-S-Coordination is also characteristic for benzothiophene complexes, for instance 322 [8,13,624] ... 

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