Coupling Pyrazine to Dithiocarbonates for Molybdopterin Model Ligands—Indispensable Tin

Abstract

Several synthetic cross-coupling procedures were (re-)evaluated for the tethering of pyrazine to dithiocarbonates. The resultant species constitute pro-ligands and can be converted by removal of the C=O moiety into ene-dithiolate ligand systems that model molybdopterin. The coupling of 2-iodopyrazine with the stannylated dithiocarbonate units mediated by copper(I)-thiophene-2-carboxylate in stoichiometric equivalents proved to be the most efficient and the only reliable route to the targeted compounds. Single-crystal X-ray structural analysis confirmed the final structures of two pursued pyrazine-derived dithiocarbonates and those of two intermediates.

Keywords

• Stille reaction
• stannylation
• copper(I)-thiophene-2-carboxylate
• 4-(pyrazin-2-yl)-1,3-dithiol-2-one ligand systems
• acetalization