Deacetylation of chiral ferrocenyl-containing β-diketones promoted by ethylene diamine: Spectroscopic and structural characterization of the fragmentation products
Résumé
It is well known that β-diketones react with primary amines, readily forming the
corresponding Schiff base derivatives. However, in the present case, the chiral
ferrocenyl-containing β-diketones, 3-(1-ferrocenylethyl)-pentane-2,4-dione (1a), 1-(4-
methoxyphenyl)-2-(1-ferrocenylethyl)-butane-1,3-dione (1b), and 1-ferrocenyl-2-(1-
ferrocenylethyl)-butane-1,3-dione (1c) react with ethylene diamine under acidic
conditions in refluxing toluene to yield, unexpectedly, their deacetylated counterparts,
3-ferrocenyl-butane-2-one (2a), 1-(4-methoxyphenyl)-3-ferrocenyl-butane-1-one (2b),
and 1,3-bisferrocenyl-butane-2-one (2c), respectively. Such deacetylation reactions are
accompagned by the formation of 2-methyl-2-imidazoline. A reaction mechanism
involving an intramolecular Michael addition followed by a retro-Mannich
rearrangement is suggested. The ketones 2a-c are fully characterized by analytical and
spectroscopic methods. Additionally, compounds 2a and 2c are authenticated by single
crystal X-ray diffraction analysis. The electrochemical behaviour of the bimetallic
complex 2c is also investigated.
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