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In Search of oligo(2-thienyl)-substituted Pyridine Derivatives: A Modular Approach to Di-, Tri- And tetra(2-thienyl)pyridines

In Search of oligo(2-thienyl)-substituted Pyridine Derivatives: A Modular Approach to Di-, Tri- And tetra(2-thienyl)pyridines

Mrinal K Bera, Paul Hommes, Hans-Ulrich Reissig

Chemistry. 2011 Oct 10;17(42):11838-43.

PMID: 21898622

Abstract:

Herein, we describe our attempts to systematically prepare a series of oligo(2-thienyl)-substituted pyridine derivatives. The crucial starting material, a β-alkoxy-β-ketoenamide, is easily available on a large scale by the reaction of lithiated methoxyallene with thiophene-2-carbonitrile and thiophene-2-carboxylic acid. This three-component reaction is followed by intramolecular cyclization to yield the suitably functionalized 2,6-di(2-thienyl)-substituted pyridine derivates. The two oxygen atoms allow the programmed activation of positions C-3, C-4, or C-5 of the pyridine ring to perform palladium-catalyzed coupling reactions with thiophene-2-boronic acid or 2-(tributylstannyl)thiophene, and alternatively, reductive removal of groups. With this concept, we were able to prepare five pyridine derivatives with 2-thienyl substituents in the 2,6-, 2,3,6-, 2,4,6-, 2,3,4,6-, and 2,3,5,6-positions. 2,3,4,5,6-Penta(2-thienyl)pyridine was not available with our methods. The UV/Vis and fluorescence spectra of all pyridines were recorded and showed a dependence on the substitution pattern and protonation state. For the protonated 2,3,5,6-tetra(2-thienyl)-substituted pyridine, a Stokes shift of about 180 nm with an emission at 515 nm was observed.

Chemicals Related in the Paper:

Catalog Number	Product Name	CAS Number	Price
AP54663784	2-(Tributylstannyl)thiophene	54663-78-4	Price
AP59020109	3-(Tributylstannyl)pyridine	59020-10-9	Price
LS7931212	5-bromobenzo[b]thiophene-2-boronic acid		Price

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