Synthesis, characterization and crystal structures of boron-containing intermediates in the reductive amination of ferrocenecarboxaldehyde to a bis(ferrocenylmethyl) amine

摘要

Reaction of ferrocenecarboxaldehyde with aqueous methylamine leads to [(methylimino)methyl]ferrocene, which is reduced to N-(ferrocenylmethyl)-N-methylamine by NaBH4. This amine reacts with ferrocenecarboxaldehyde and NaCNBH3 to give the tertiary ammonium salt, di(N-(ferrocenylmethyl))-N-methylammonium cyanoborohydride. Hydrolysis of the NaCNBH3 reaction mixture produces the free amine, di(N-(ferrocenylmethyl))-N-methylamine. Thermolysis of di(N-(ferrocenylmethyl))-N-methylammonium cyanoborohydride in refluxing tetrahydrofuran converts it to the cyanoborane adduct, di(N-ferrocenylmethyl)-N-methylaminecyanoborane, with elimination of H-2. The new compounds are fully characterized by using spectroscopic and physical methods, including X-ray crystal structure determinations of di(N-(ferrocenylmethyl))-N-methylammonium cyanoborohydride, di(N-(ferrocenylmethyl))-N-methylamine, and di(N-(ferrocenylmethyl))-N-methylamine-cyanoborane. (c) 2006 Elsevier B.V. All rights reserved.