Dithienyls

Functionalized conducting monomers can be deposited on electrode surfaces aiming for covalent attachment or entrapment of sensor components. Electrically conductive polymers (qv), eg, polypyrrole, polyaniline [25233-30-17, and polythiophene/23 2JJ-J4-j5y, can be formed at the anode by electrochemical polymerization. For integration of bioselective compounds or redox polymers into conductive polymers, functionalization of conductive polymer films, whether before or after polymerization, is essential. In Figure 7, a schematic representation of an amperomethc biosensor where the enzyme is covalendy bound to a functionalized conductive polymer, eg, P-amino (polypyrrole) or poly[A/-(4-aminophenyl)-2,2 -dithienyl]pyrrole, is shown. Entrapment of ferrocene-modified GOD within polypyrrole is shown in Figure 7. 

Ethylene, /3-(dimethylamino)-nitro-in pyrrole synthesis, 4, 334 Ethylene, dithienyl-in photochromic processes, 1, 387 Ethylene, furyl-2-nitro-dipole moments, 4, 555 Ethylene, l-(3-indolyl)-2-(pyridyl)-photocyclization, 4, 285 Ethylene, l-(2-methyl-3-indolyl)-l,2-diphenyl-synthesis, 4, 232 Ethylene, (phenylthio)-photocyclization thiophenes from, 4, 880 Ethylene carbonate C NMR, 6, 754 microwave spectroscopy, 6, 751 photochemical chlorination, 6, 769 synthesis, 6, 780 Ethylene oxide as pharmaceutical, 1, 157 thiophene synthesis from, 4, 899 Ethylene sulfate — see 2,2-dioxide under 1,3,2-Dioxathiolane... 

To a solution of thienyl magnesium bromide prepared from 21.4 g of magnesium and 144 g of 2-bromothiophene are added 39.B g of ethyl 4-dimethylaminocyclohexylcarboxylate. The mixture is ailowed to warm to room temperature and stirred for an additional six hours. The reaction mixture is then decomposed with dilute ammonium chloride solution and extracted with ether. The combined ether extracts are extracted thoroughiy with 10% hydrochloric acid and the acid solution made alkaline with ammonium hydroxide. The aqueous solution is extracted with chloroform which is then washed with water, dried and evaporated to a residue in vacuo. Recrystallization of the residue from hexane yields Oi.O -dithienyl-4-dimethyl-aminocyclohexyl carbinol, melting point 156°C to 157°C after recrystallization from benzene. 

TABLE 5. Observed absorption maxima (Amax) of all- ratts,-a,G)-dithienyl-polyenes in dichloromethane37... 

Figure 33 shows the UPS spectra of 2,5-bis(diphenylmethy-lene)-2,5-dihydrothiophene and di-hydroselenophene, as compared with that of 2,5-bis(dithienyl methy-lene)-2,5-dihydrothiophene, together with the spectra of benezene and thiophene for references, irrespective of the central ring with sulphur or selenium the UPS spectra are found to be almost same. However, the spectra were significantly different with changing the substituent rings at the exocyclic double bonds from the phenyl to the thienyl groups. In both the phenyl and the thienyl substituents, the spectra are very similar to those of benzene and thiophene... 

Applications of the aforementioned methodology are also found in the total synthesis of plagiochin D to link a 16-membered biaryl system [47], as well as to the intramolecular cyclization of di-benzyl halides [45, 48]. Additional examples include dithienothiophene (40) from dithienyl bromide 39 [49] and carbazole 42 from diarylbromide 41 [50]. 

DITHIENYL SULFIDE, 50 75 1,3-Dithiolanes, 54, 37 Diynes, preparation, 50, 101 n-Dodecane, 53, 108 Double bond, exocyclic, selective hydrogenation, 53, 65 DURENE, I0D0—, 51, 94... 

By treatment with NaBH4 in aqueous NaOH in the presence of dithienyl ditelluride, a-phenylseleno carboxylic esters and malonates, as well as a-phenylseleno carboxylic acids, are deselenylated to the corresponding seleno-lree acids in good yields. The selective removal of the seleno group without dealkylation of the ester moiety is achieved by the methods depicted in the scheme. 

The phenylation of thiophene with benzoyl peroxide gave a considerable amount of 2,2 -dithienyl one suggested mechanism involved the formation of 2-thienyl radicals by oxidation, and their subsequent dimerization. More recent studies indicate that the 2,2 -dithienyl is formed through an initial addition of benzoyloxy radicals to the thiophene nucleus followed by dimerization of the resulting radical and loss of two molecules of benzoic acid (Scheme 15). 

Photochromic dithienyl- and dibenzothienylethenes, particularly those containing the central 1,2-perfluorocyclopentene fragment, belong to the major group of compounds, which have attracted the attention of researchers in the field of information storage (optical memory) and optical switches because their starting (A) and cyclic (B) forms are, in most cases. 

The synthesis of dithienyl photochromes containing a maleic anhydride fragment (a furan-2,5-dione fragment) as the ethene bridge was a difficult problem. Initially, vicinal dinitriles 160 and 162 were used as the starting compounds (Scheme 49). But the latter compounds give a maleic anhydride only in the cis conformations. The separation of the cis and trans isomers is an additional time-consuming laborious problem. 

The conventional and efficient method for the synthesis of dithienyl-maleimide 185, according Scheme 56, was described by Chinese researchers (06TL9227). 2,3-Bis(5-bromo-2-methylthiophen-3-yl)fumaronitrile 184 was hydrolyzed with sodium methoxide-methanol followed by N-meth-ylation with potassium ferf-butoxide and iodomethane to give the target compound 2,3-bis(5-bromo-2-methylthiophen-3-yl)-N-methylmaleimide. Subsequent modification of the latter afforded 186 containing two ferrocene fragments. 

More recently, a new method was developed (05MI3) for photochromic 4,5-dithienyl(dibenzothienyl)-l,3-dithiol-2-ones 229 and dithiol-2-thiones 230 from acetylene derivative 228 (Scheme 66). Compounds 230 are good building blocks for the design of photochromic fluorophores. 

DITHIENYL SULFIDE, 50, 75 Diynes, preparation, 50, 101 DURENE, IODO-, 51, 94... 

Wynberg and Bantjes studied the pyrolysis of thiophene at 800°-850° by mass spectrometry they established the presence of isomeric dithienyls, benzo[6]thiophene, and traces of naphthalene, isomeric phenylthiophenes, and thienothiophenes, besides unreacted thiophene and carbon disulfide. 

Dithienyl sulfides have been used for the synthesis of other isomeric dithienothiophenes, the former being obtained by the method of Fyodorov and Stoyanovich from thienyllithium and dithienyl disulfides. Dithienyl dsulfides were prepared from thiophene or 3-bromo-thiophene in high yields (Scheme 11). 

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