Intramolecular cyclization of 6-amino-5-[2-substituted-2-(cyanovinyl)]amino-1,3-dimethyluracil: synthesis of 9-deazaxanthine derivatives and 8-(cyanomethyl)theophylline
New air-stable zinc complexes formed from cyanoacrylate- and methylenemalonate-based [N2O2]-ligands and their role as catalysts in epoxide–CO2 coupling