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A study of HT regioregular polythiophenes and 3-thienyl organometallic reagents: Using Rieke metals as an important synthetic tool
Abstract
Attention has been paid to organic and polymer synthesis using Rieke metals, highly activated metals. Recently, Rieke Zinc is found to undergo chemoselectively oxidative addition to dihaloarylenes affording monometallation products. The polycondensation of these haloaryl zinc halides catalyzed by Ni- or Pd-complexes provides a series of polyarylenes. The most significant case is the regiocontrolled synthesis of poly(3-alkylthiophenes) in which the regioselective oxidative addition of Rieke Zinc to 2,5-dibromo-3-alkylthiophenes generating 2-bromo-5-bromozincio-3-alkylthiophenes is the key step. In order to prepare polythiophene compounds with higher conductivities, the regiocontrolled approach has been developed to synthesize regioregular poly (3-(alkylthio)thiophenes). Similarly, 2-bromo-3-(alkylthio)-5-(bromozincio)thiophenes, prepared by the oxidative addition of Rieke Zinc (Zn$\sp*$) to 2,5-dibromo-3-(alkylthio)thiophenes, undergo the polycondensation and transform to highly HT regioregular poly (3-(alkylthio)thiophenes) in the presence of Ni(DPPE)Cl$\sb2$. The structure and the properties of the polymers are investigated via NMR, FTIR, UV-Vis, X-ray spectroscopies. The study indicates that the polymers have a narrow band gap and a high conductivity. 3-Lithiothiophene is not regiostable in ethereal solvents. However, a regiostable form of this organolithium is prepared by a THF inducing metal-halogen exchange reaction in hexanes. The regiostable 3-lithiothiophene affords a facile synthesis for 3-functionalized thiophene molecules. Currently, a novel synthetic route for 3-thienyl organometallic reagents has been explored as the oxidative addition of Rieke Zinc and Rieke Magnesium to 3-iodothiophene. Thus prepared thienyl organometallic reagents are regiostable and used as important precursors for thiophene derivatives, such as 3-functionalized-aryl thiophenes.
Subject Area
Organic chemistry|Polymers
Recommended Citation
Wu, Xiaoming, "A study of HT regioregular polythiophenes and 3-thienyl organometallic reagents: Using Rieke metals as an important synthetic tool" (1996). ETD collection for University of Nebraska-Lincoln. AAI9712533.
https://digitalcommons.unl.edu/dissertations/AAI9712533