Stereodynamics of C-C and C-N rotation in furan and thiophene omicron-amino thioaldehydes and aldehydes

The carbon-carbon rotational barrier about the Ar-CHS bond and carbon-nitrogen rotational barrier near the Ar-NH2 bond were analyzed in furan and thiophene omicron-amino thioaldehydes. Nuclear magnetic resonance analysis of thioaldehydes in DMSO indicated the presence of rotational conformers. The minor rotamer exhibited a S,NH2-anti structure while the major rotamer exhibited a S,NH2-syn structure. Furthermore, the delocalization of the amino nitrogen lone pair occurred to a larger extent with the thiophene derivatives of omicron-amino thioaldehydes.