Al-Jumaili, Mustafa
(2019)
Studies in Thiophene Chemistry for Organic Electronic Materials.
PhD thesis, University of Nottingham.
Abstract
Thiophene-based organic semiconductor materials have seen important growth in the last two decades owing to their potential applications in many different areas. Overall, this thesis details attempts to develop rapid, efficient, cheap and scalable syntheses of small molecules and monomers of thiophene-based molecules.
After an introductory Chapter, the second Chapter in this thesis focuses on the synthesis of 7-R-anthra[2,3-b]thiophenes derivatives 11a-d (R = H, Me, iPr, OMe) and naphtho[2,3-b:6,7-b']dithiophene 12. Existing synthetic methods for the known anthra[2,3-b]thiophene 11a and naphtho[2,3-b:6,7-b']dithiophene 12 require multi-steps, toxic reagents, expensive starting materials and give low yields. However, we prepared these 7-R-anthra[2,3-b]thiophene derivatives 11a-d (R = H, Me, iPr, MeO) in only three steps (with average overall yields of >50%) starting from (E)-4-RC6H4CH2(HOCH2)C=CI(CH2OH). The latter are commercial or readily prepared from 2-butyne-1,4-diol 1 and ArCH2Cl 4 (both typically costing <4 pence /g) at 10 g scales. These procedures allow selective formation of (otherwise unattainable) higher solubility 7-substituted. Similar methods allowed the preparation of naphtho[2,3-b6,7-b']dithiophene 12 using equally low-cost starting materials in only three steps.
A third Chapter of this report focuses on efficient synthesis and characterization of new derivatives of 3,4-ethylenedithiothiophene (EDTT) 149a-d starting from tetrabromothiophene 146. Selective 2,5-dilithiation followed by reaction with a range of aldehydes gives diols 147a-e as mixtures of diastereomers. Only the 2 and 5 positions in tetrabromothiophene 146 react leaving the 3,4-bromides for further elaboration. The diols 147a-e are oxidised to their corresponding diketones 148a-e using activated MnO2. Reaction with 1,2-ethanedithiol, by addition-elimination, provides access to novel monomers 149a-d for the preparation of conjugated copolymers of 3,4-ethylenedithiothiophene (EDTT). A range of these monomers can be attained by applying the synthesis of a series of ketones and this is applicable to further synthesis of π-extended thiophene-based organic semiconductors.
Chapter four of this thesis composed of two parts. The first part focus on the synthesis of 3,4-ethylenedioxythiophene (EDOT) dialdehyde derivatives 177 by efficient alternatives to literature chemistry, while a second part reports the optimisation of a synthesis of novel vinyl thiophenes materials.
A final Chapter gives full experimental details of all the compounds prepared in the thesis and their spectroscopic data.
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