130562-99-1Relevant academic research and scientific papers
PROTONATION AND ELECTROPHILIC TRICHLOROMETHYLATION OF 2,5- AND 2,4-DICHLOROTHIOPHENES
Belen'kii, Leonid I.,Gromova, Galina P.,Krayushkin, Mikhail M.
, p. 365 - 368 (2007/10/02)
Trichloromethylation of 2,5-dichlorothiophene, 1, and 2,4-dichlorothiophene, 2, with CCl4 and AlCl3 has been studied.It could be shown that in the case of 1 the reaction was directed to position 3 with formation of 2,5-dichloro-3-(trichloromethyl)thiophene, 3, the process being complicated by the formation of the isomeric 3,5-dichloro-2-(trichloromethyl)thiophene, 4, and 4,5-dichloro-2-(trichloromethyl)thiophene, 5, as well as linked products, i.e. a mixture of bis(dichlorothienyl)dichloromethanes (6).Trichloromethylation of 3 smoothly leads to 4, along with a small amount of bis(3,5-dichloro-2-thienyl)dichloromethane.It has also been found that, as a result of protonation, under the effect of HCl and AlCl3, the 2,5-dichloro derivative 1 was converted into the 2,4-dichloro isomer 2, which, under the reaction conditions, exist in the form of ?-complex, i.e. the 2H-3,5-dichlorothiophenium ion, stable at room temperature.The mechanism of trichloromethylation of 1, including the ipso-attack by the CCl3+ cation and isomerization during protonation, is discussed.
