Synthesis of 2,3-Dihydrothieno[2,3-b]-1,4-dithiine, 2,3-Dihydrothieno-[3,2-b]-1,4-oxathiine, 2,3-Dihydrothieno[2,3-b]-1,4-oxathiine and Their Transformation­ into Corresponding End-Capped Oligomers [1]

Abstract

Three new heterocyclic parent compounds, 2,3-dihydrothieno[2,3-b][1,4]dithiine (TDT), 2,3-dihydrothieno[3,2-b][1,4]oxathiine (TOT), and 2,3-dihydrothieno[2,3-b][1,4]oxathiine, have been synthesized by acid-catalyzed transformations starting from 3-methoxythiophene. Two of the new compounds have been transformed to the corresponding end-capped dimeric, trimeric and tetrameric oligothiophenes. These oligomers show very stable cationic and dicationic states as judged by cyclic voltammetry, and their UV-Vis spectra are considerably red-shifted compared to previously synthesized end-capped oligomers.

Key words

ring-closure - tandem reactions - oligothiophenes - Suzuki coupling

References

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2

Present address: Acreo AB, Bredgatan 34, SE-602 21 Norrköping, Sweden.

3

Present address: Unit for Organic Chemistry, Department of Biosciences, Karolinska Institute and Södertörn University College, Novum Research Park, SE-141 57 Huddinge, Sweden.

10

In order to have a useful shorthand nomenclature for the oligothiophenes, we named TDT for thienodithiine 5 and TOT for thienooxathiine 7. The oligothiophenes were then called TDTnT for the dithiino end-capped series, and TOTnT for the oxathiino end-capped series, where n is the number of thiophene units, as for the ECnT oligomers [7] . For instance, TOT3T 29 is a terthiophene, which is end-capped with thioxano rings.

11

A literature search with Beilstein Commander and Scifinder Scholar in May 2003 found 20 substances containing 5 as a substructure, other than those reported by us in preliminary communications. Only 3 of these contain a peripheral ethylenedithio bridge. No compound with the substructure 6 was found, and only 3 compounds based on 7.