Efficient preparation of photoswitchable dithienylethene-linker-conjugates by palladium-catalyzed coupling reactions of terminal alkynes with thienyl chlorides and other aryl halides

Marc Zastrow, Sujatha Thyagarajan, Saleh A. Ahmed, Paul Haase, Sabine Seedorff, Dmitri Gelman, Josef Wachtveitl, Elena Galoppini, Karola Rück-Braun*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Three photochromic dithie-nylethene-linker-conjugates with an adamantane core containing different spacer lengths and footprint areas with carboxylic anchoring groups are synthesized. The synthetic routes start either from the ethynylene-linker 5 or the iodo-substituted linker 8. Reaction conditions for the final Sonogashira coupling step between ethynylenelinker 5 with the chloro-substituted dithienylethene 4 in the presence of [PdCl 2(CH3CN)2]/X-Phos and Cs2CO 3 or K3PO4 are optimized using 2-chloro-5-methylthiophene (9) and triethylsily-lacetylene or triisopropylsilylacetylene (10a,b) as model compounds. Experimental conditions are found to suppress the activation of the C(sp)-Si bond in TIPS-acetylene 10 b, a reaction leading to a subsequent cross-coupling reaction to form by-product 12. Furthermore, activation of the C(sp)-Si bond in the presence of the fluorinated backbone of the chloro-substituted di-thienylethene 4 can also be prevented. The photochromic properties of the conjugate 3 and its precursor dithienyl-ethene 7b are also investigated.

Original languageEnglish
Pages (from-to)1202-1212
Number of pages11
JournalChemistry - An Asian Journal
Volume5
Issue number5
DOIs
StatePublished - 3 May 2010

Keywords

  • Cross-coupling
  • Palladium
  • Photochromism
  • Thiophene
  • Tripodal ligands

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