Coupling Pyrazine to Dithiocarbonates for Molybdopterin Model Ligands-Indispensable Tin

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.

Automated summary

Several synthetic cross-coupling procedures were evaluated for tethering pyrazine to dithiocarbonates. The resulting compounds can serve as pro-ligands and can be converted into ene-dithiolate ligand systems resembling molybdopterin by removing the C=O moiety. The coupling of 2-iodopyrazine with stannylated dithiocarbonate units mediated by copper(I)-thiophene-2-carboxylate in stoichiometric equivalents proved to be the most efficient and reliable method for synthesizing the targeted compounds.