Aminomethyl-Substituted Ferrocenes and Derivatives: Straightforward Synthetic Routes, Structural Characterization, and Electrochemical Analysis

Abstract

A variety of aminomethyl-substituted ferrocenes and the parent compounds (iminomethyl)ferrocenes, azaferrocenophanes, and diferrocenylamines can be selectively synthesized from reductive amination of 1,1′-diformylferrocene or formylferrocene. The optimized one- or two-step reactions have delivered 13 new compounds, isolated in 65–97% yields, which include tertiary (ferrocenylmethyl)amines and azaferrocenophanes by using NaBH(OAc)3 as a mild reducing agent and (iminomethyl)ferrocenes and secondary (ferrocenylmethyl)amines by using LiAlH4. X-ray structures of representative members of these ferrocene derivative families have evidenced the preferred conformation adopted by ferrocene backbones, in which surprisingly the steric hindrance is apparently not systematically minimized. 15N NMR measurements on aminomethyl-substituted ferrocenes and derivatives are provided for the first time, establishing benchmark values ranging from −330 to −305 ppm (nitromethane δ 0 ppm). The cyclic voltammetry of these species evidences two clearly distinct oxidation potentials related to the iron(II) center and the amino function. These aminomethyl-substituted ferrocenes are potentially valuable for further ortho-directed functionalization of ferrocene.

N‐Allyl‐N‐ferrocenylmethylamines andansa‐Ferrocenylmethylamines: Synthesis, Structure, and Biological Evaluation

“…Reactions of 2 with two equivalents of allylamine provided the expected 1,1′‐diamine 7 in a rather moderate yield (38 %) as the only isolable product [20] . Contrary to the previous report on reactions of 1,1′‐ferrocenedicarboxaldehyde with secondary amines, [15b] the reactions with N ‐allylmethylamine or N ‐allylaniline appeared as incomplete, also when a ten‐fold excess of the amine was used. Consequently, an unexpected and simple route to aminomethyl aldehydes (R=Me or Ph) and aminomethyl alcohol (R=Ph) was discovered.…”

“…Compounds analogous to 14 have been previously obtained from 2 and primary alkyl amines, such as N ‐butylamine, [15a,b] or by condensation of 1,1′‐ferrocenedimethanol with primary amines [12] . Formation of the bridge is unambiguously confirmed by a single‐crystal X‐ray diffraction analysis ( see below ).…”

Gold‐Catalyzed Suzuki Coupling of ortho‐Substituted Hindered Aryl Substrates

“…We recently reported the high-yielding diastereoselective synthesis of planar chiral (N,N',P,P')-hybrid organometallic ligands L1-L3 (L1:R = Et, R' = Ph; L2:R= Et, R' = iPr; L3:R =À CH 2 (CH 2 ) 2 CH 2 À,R ' = Ph). [18] We used these racemates for synthesizing dinucleargold complexes AuL1-AuL3 (Scheme 2).…”

1-Cyano-1′-ethynyl-ferrocene: Synthesis and reaction chemistry

“…Further characteristic for 6 is the appearance of an irreversible oxidation process at 460 mV, which can be assigned to the amine NEt 2 oxidation and is typical for alkyl-substituted amines [70e72]. The irreversibility of this process can be explained by the strong tendency of oxidized amines to undergo follow-up reactions, like iminium ion formation by deprotonation [73] or dealkynation [74]. Also an attachment of the oxidized species towards the carbon and platinum surfaces is possible [75].…”