3- Ethyl thiophene

This activation of the ortho position is most strikingly illustrated in the reactivity of 2,5-dimethylthiophene, which competitive experiments have shown to undergo the SnCb-catalyzed Friedel-Crafts reaction more rapidly than thiophene and even 2-methylthiophene. The influence of the reagent on the isomer distribution is evident from the fact that 2-methoxythiophene is formylated and bromi-nated (with A -bromosuccinimide) only in the 5-position. Similarly, although 3-bromo-2-methylthiophene has been detected in the bromi-nation of 2-methylthiophene with bromine, only the 5-isomer (besides some side-chain bromination) is obtained in the bromination of alkylthiophenes with A -bromosuccinimide. ° However, the mechanism of the latter type of bromination is not established. No lines attributable to 2-methyl-3-thiocyanothiophene or 2-methyl-3-chIoro-thiophene could be detected in the NMR spectra of the substitution products (5-isomers) obtained upon thiocyanation with thiocyanogen or chlorination with sulfuryl chloride. 2-Methyl- and 2-ethyl-thiophene give, somewhat unexpectedly, upon alkylation with t-butyl chloride in the presence of Feds, only 5-t-butyl monosubstituted and... 

Cases of the S-coordinated rhodium and iridium are quite scarce. To complete the picture, we next consider the possibilities of S-coordination using complicated derivatives of thiophene. 2,5-[Bis(2-diphenylphosphino)ethyl]thiophene is known to contain three potential donor sites, two phosphorus atoms and the sulfur heteroatom, the latter being a rather nucleophilic center (93IC5652). A more typical situation is coordination via the phosphorus sites. It is also observed in the product of the reaction of 2,5-bis[3-(diphenylphosphino)propyl]thiophene (L) with the species obtained after treatment of [(cod)Rh(acac)] with perchloric acid (95IC365). Carbonylation of [Rh(cod)L][C104]) thus prepared yields 237. Decarbonylation of 237 gives a mixture of 238 and the S-coordinated species 239. Complete decarbonylation gives 240, where the heterocycle is -coordinated. The cycle of carbonylation decarbonylation is reversible. 

Figure 9.19 Chemical structure of poly 3-[2-((S)-2-methylbutoxy)ethyl]thiophene. Number of repeating units is 50.

Fig. 7.11. Metabolism of S-(l- [(2,3,4,5-tetrahydro-2-oxothiophen-3-yl)amino]carbonyl ethyl) thiophene-2-carbothioate (MR 889, 7.71) in rats to the active thiol metabolite homocysteine thiolactone thiolactamide (7.72) and to thiophene-2-carboxylic acid (7.73) [154], Subsequent reactions of hydrolysis and conjugation are also shown.

Alkylation of intermediate with 2-(2-bromo-ethyl)thiophene affords the corresponding thiophene-... 

Thienylzincates are available using lithium di-zW-butyltetramethylpiperidinozincate (TMP-zincate) <1999JA3539> thus, ethyl thiophene-3-carboxylate is easily metallated at C(2) at room temperature, subsequent reaction with iodine giving ethyl 2-iodothiophene-3-carboxylate in 89% yield. Similarly ethyl thiophene-2-carboxylate gives the 5-iodo derivative in 62% yield. 

C7H802S ethyl thiophene-2-carboxylate 2810-04-0 491.15 43.034 1,2 10990 C7H9NO 3-amino-o-cresol 53222-92-7 480.51 42.014 2... 

C7H10O trans,trans-2,4-heptadienal 4313-03-5 357.65 30.394 1,2 11230 C7H10S 2-methyl-4-ethyl thiophene 13678-54-1 436.15 38.411 1,2... 

C7H10S 2-methyl-5-ethyl thiophene 40323-88-4 204.65 12.073 2 11700 C7H14 trans-1,2-dimethylcyclopentane 822-50-4 155.58 7.398 1... 

Chart 2.2 Chemical structures of N-M-propyl-(3-thiophen-2-yl-ethyl)-thiophen-3-ylethy 1-amine (29), N- -propyl-(2-thiophen-2-yl-ethyl)-thiophen-3-ylethyl-amine (30). 

N- -Propyl-(3-thiophen-2-yl-ethyl)-thiophen-2-yI-acetamide (48) To a solution of amine 47.HC1 (500 mg, 2.4 mmol) dissolved in dichloromethane (50 mL) and 10 % NaOH (10 mL) was added 2-thienylacetylchloride (2 mL). The mixture was stirred for 3 h at RT and poured into water. The organic layer was separated and the aqueous layer was extracted with dichloromethane. The combined organic layers were washed with brine, dried over Na2S04 and concentrated under reduced pressure. The oil was purified over a Si02-column with dichloromethane as eluent. Evaporation of the dichloromethane yielded 660 mg (93 %) oil H NMR (CDCI3) 8 0.9 (t, 3H, J = 7.3 Hz), 1.4-1.7 (m, 2H), 2.8-2.9 (m, 2H), 3.1-3.2 (m, 1H), 3.3-... 

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