Butyl thiophene

Stable 2,4-disubstituted thiophene-3-carbonitrile oxides 7 and 3,5-di(t-butyl)-thiophene-2-carbonitrile oxide 8 were synthesized from respective aldoximes by the similar one-pot procedure (33—35). 

The heterocyclic 2,5-dilithio-3,4-di-(f-butyl)thiophene (78) could be generated by Nakayama and coworkers, starting from the corresponding 2,5-dibromo compound 77. The bromide-lithium exchange reaction was effected using two equivalents of... 

Friedel-Crafts alkylation of 2,5-dimethylthiophene with f-butyl chloride and A1C13 gave only the mono-r-butylated product (49) and none of the expected di-f-butylated thiophene (50). In order to facilitate di-r-butylation at positions 3 and 4, the substituents at 2 and 5 were tied back in the thiophenophane (51). This on alkylation gave, unexpectedly, the rearranged mono-f-butyl derivatives (52 30%) and (53 57%), and the di-f-butyl derivative (54 12%). The structures of the products were proved by NMR, Raney nickel desulfurization and independent synthesis (75T2551). One other such isomerization under Friedel-Crafts conditions had been previously reported (65JOC1058) 2,5-di-f-butylthiophene isomerizing to 2,4-di-f-butylthiophene. 

In alkylthiophenes38,40 [see Fig. 2, mass spectrum of a-(n-butyl)-thiophene] cleavage reactions which proceed with ring enlargement are highly favored, (42)->[44], (43)->[44] ... 

Poly(3-butyl)thiophene with cited density of head-to-tail units. t... 

Procedure. Isobutylene (gaseous) is introduced in a rapid stream to the well-stirred mixture of thiophene and sulfuric acid over a period of about one hour. The temperature is raised to 60-70° before addition of the isobutylene and maintained in that range throughout the addition by means of a water bath. The organic layer is decanted from the catalyst layer and washed with dilute alkali (KOH or NaOH), dried over calcium chloride, and distilled in a 10-plate fractionating column. The cut boiling between 162 and 170° is a mixture of 2- and 3-/rr/-butyl-thiophene. These isomers are best separated in a 60-plate column by a double fractionation. Pure 2-terf-butylthiophene boils at 163.9°,... 

Pyrimidine cyclization based on 3-amino derivatives of thiophene 03MI47. Studies on 7t-face selective additions with 3,4-di-Art-butyl thiophene 1-oxide and 1-imide 03YGK1106. 

The ultra-thin organie film formation on TiOj templates was effectively promoted through the speeifi-eally designed, bifunctional self-assembly molecules (SAM) 5-eyano-2-(butyl(4-phosphonie acid))-3-butyl-thiophene (CNBTPA), whereas DBQT and DBST did not improve their layer structure when they were evaporated on the SAM layer (images not shown). 

Methoxycarbonylamino-3-athoxycarbonylamino-2-(4-carboxy-butyl)-tetrahydro-durch katal. Hydrierung von 4- Mcthoxycarbonyl-amino-3-athoxycarbonylamino-2-(4-carb-oxy-butyl)-thiophen mit Pd/C 364 2-Methoxycarbonyl-2,5-dihydro- 639 2-Methoxy methyl- 362 2-Methyl- 55... 

We will show that a comparison of results between (PBT(FeCl3)) and polycondensation of the dibromi-nated monomer (PBT(MgX)) does not reveal the effect of molar mass, although the molar mass obtained is different. In order to investigate this effect, a more accurate study on fractionated samples of poly(3-butyl thiophene) has to be carried out. 

Table 8.3. Molar masses, defect late, conductivity and c iogh7. are given as a function of doping level for samples of each fraction of poly(3-butyl thiophene)...

Various organic sulfides present in Allium have been found to have anticar-cinogenic activity. For example, allyl sulfide, a constituent of garlic oil, inhibited colon cancer in mice exposed to 1,2-dimethylhydrazine, and allyl methyl trisulfide, allyl methyl disulfide, aUyl trisulfide, and allyl sulfide all inhibited benzo[a]pyrene-induced neoplasma of the forestomach and lung in female mice (55). Lam et al. (Chapter 22) investigated the ability of 2-n-butyl thiophene, a constituent of roast beef aroma, to inhibit chemically induced carcinogenesis in three different tumor systems. This compound was found to be effective in the forestomach, lung, and colon models. 

Photochemistry of Thiophens.—Wynberg and co-workers have continued their investigations on the photochemistry of thiophens, and an excellent essay by Wynberg on the photochemistry and other aspects of thiophen chemistry has recently been published. The photoisomerizations of thiophens are also discussed in a detailed review article on the photoisomerization of five-membered heterocyclics. Irradiation of 2-methyl-, 2-benzyl-, 2-neopentyl-, and 2-t-butyl-thiophens leads to their irreversible transformation to the corresponding 3-substituted derivatives in 8— 27% yields. 2,5-Di-t-butylthiophen rearranges irreversibly to the 2,4-isomer, which is remarkably stable under the reaction conditions. Irradiation of 2,2 -bithienyl leads to 2,3 -bithienyl and a small amount of benzo[6]thio-phen. 2,3 -Bithienyl affords 3,3 -bithienyl and benzo[6]thiophen as major products. 5,5 -Dideuterio-2,2 -bithienyl gives 5,5 -dideuterio-2,3 -bithienyl... 

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