SELECTIVE ELECTROCHEMICAL MONOSILYLATION AND POLYSILYLATION OF HALOTHIOPHENES

Citation
D. Deffieux et al., SELECTIVE ELECTROCHEMICAL MONOSILYLATION AND POLYSILYLATION OF HALOTHIOPHENES, Organometallics, 15(8), 1996, pp. 2041-2046
Citations number
35
Categorie Soggetti
Chemistry Inorganic & Nuclear","Chemistry Inorganic & Nuclear
Journal title
ISSN journal
02767333
Volume
15
Issue
8
Year of publication
1996
Pages
2041 - 2046
Database
ISI
SICI code
0276-7333(1996)15:8<2041:SEMAPO>2.0.ZU;2-G
Abstract
Electrochemical trimethylsilylation of mono- and polyhalothiophenes (h al = Cl, Br) has been examined. In order to predict the selectivity of the reaction in accordance with the halogen position on the ring, the reduction potentials of the commercially available halothiophenes hav e been determined by cyclic voltammetry. Thus, as expected, the bromo derivatives are more easily reduced than the chloro analogs, and the 2 -position is more reactive than the S-position. We obtained 2- and 3-( trimethylsilyl)thiophenes, 2-(trimethylsilyl)-3 (or 5)-halothiophenes, 2-(trimethylsilyl)-3,4,5-trihalothiophenes, 2,5-bis(trimethylsilyl)th iophene, 2,5-bis(trimethylsilyl)-3,4-dihalothiophenes and 2,3,5-tris(t rimethylsilyl)-4-halothiophenes with an excellent selectivity. In cont rast, the silylation of 2-(trimethylsilyl)3-halo- and 2,3,5-tris(trime thylsilyl)-4-halothiophenes occurred with ring opening and afforded 1, 1,4,4-tetrakis(trimethylsilyl)-1,2-butadiene and hexakis(trimethylsily l)-2-butyne, respectively. A coherent interpretation of the synthetic results is proposed in correlation with the measured potential values.