Synthesis of Novel Five- and Six-Membered Ferrocene-Containing Heterocycles and Heteroaromatics via Cyclocondensation of 1-Ferro­cenyl-3,3-bis(methylthio)prop-2-en-1-one with Various Bifunctional Nucleophiles

Abstract

Synthesis and reactions of 1-ferrocenyl-3,3-bis(methylthio)prop-2-en-1-one as a versatile 1,3-bielectrophilic synthon leading to a range of novel ferrocene-containing five- and six-membered heterocycles and heteroaromatics has been reported. Thus its cyclocondensation with various bifunctional heteronucleophiles, such as hydrazine­, phenylhydrazine, hydroxylamine, guanidine, and amidine, affords­ a range of ferrocene-substituted pyrazoles, oxazoles, and pyrimidines in highly regioselective manner. Synthesis of few ferrocenyl-substituted pyridines and thiophenes has also been described. Similarly cycloaromatization of this ferrocene-substituted α-oxoketene dithioacetal with anions generated from (het)arylacetonitriles provides a facile entry to ferrocene-substituted heteroaromatics in good yields. Synthesis of a few 2-ferrocenylvinyl-substituted heterocycles, such as pyrazoles, isoxazoles, and pyrimidines, via cyclocondensation of a novel 5-ferrocenyl-1,1-bis(methylthio)penta-1,4-dien-3-one with phenylhydrazine, hydroxylamine, and guanidine has also been reported.