Synthesis of Ferrocenyl-Substituted Heterocycles: The Beneficial Effect of the Microwave Irradiation
The synthesis of ferrocenyl-substituted thiophenes, furans, pyrroles, pyrimidine and pyrazole has been studied. 2-Ferrocenylpyrroles were prepared from ferrocenyl ketoximes and acetylene in DMSO - KOH mixture whereas 3-chloro-3-ferrocenylacrylaldehydes and thioglycolic or glycolic acids were the starting materials for the synthesis of the thiophene and furan derivatives. The yields were significantly enhanced when the reactions were carried out in a microwave oven. The lower stability of 2-ferrocenylfuran in comparison with 2-ferrocenylthiophene is discussed on the basis of semiempirical quantum chemistry calculations.