Ferroceneboronic Acid and Derivatives: Synthesis, Structure, Electronic Properties, and Reactivity in Directed C–H Bond Activation

Abstract

Known since 1959, ferroceneboronic acid (1) and its derivatives have been mainly used as polyol sensors and in crosscoupling reactions. However, a literature survey revealed that there is not a paper describing the full characterization of ferroceneboronic acid derivatives and that useful boron protecting groups have not been studied in the ferrocene series. Here, we present an optimized multigram scale synthesis of the known ferroceneboronic acid (1) using a phase-switch purification process. It was furthermore functionalized to reach the diaminonaphthalene (FcB(dan), 15), anthranilamides (FcB(aam), 16; FcB(Me-aam), 17 and 18), potassium trifluoroborate (FcBF3K, 19), triolborate (FcB(triolborate), 20) and N-methyliminodiacetic acid (FcB(MIDA), 21) derivatives. Their structures were unambiguously assigned by NMR and X-ray analysis and the data collected provided a general overview of the electronic and structural features of these compounds. From the data obtained, B(dan) and B(amm) groups were classified as electron-withdrawing whereas trifluoroborate and triolborate behave as electron-donating groups. We report the first catalytic silylation of ferrocene C-H bonds to access di-and trisubstituted derivatives. Catalytic borylation was also attempted, highlighting a switch of regioselectivity that was unambiguously assigned by X-ray analysis.

Voltammetric characterisation of diferrocenylborinic acid in organic solution and in aqueous media when immobilised into a titanate nanosheet film

“…In 11 B NMR a characteristic peak is observed at 46.0 ppm consistent with sp 2 -boron, which compares to the 11 B chemical shift for ferroceneboronic acid of 31.0 ppm. 2 For further details and data, see ESI. † Fc 3 B (2) was also characterised (see ESI Fig.…”

“…Ferroceneboronic acid as an electrochemically active boronic acid has been used previously in electroanalytical sensing protocols. 1,2 Boronic acid moieties [R 1 B(OH) 2 ] can bind nucleophiles and in particular vicinal diols or other polyols 3,4 and importantly to glucose. 5 From this, a range of sensing applications have been developed, [6][7][8] including applications with electrochemical detection.…”

Chiral Bidentate Boryl Ligand-Enabled Iridium-Catalyzed Enantioselective Dual C–H Borylation of Ferrocenes: Reaction Development and Mechanistic Insights

“…However, establishing other types of chirality through an asymmetric C–H borylation protocol has lagged behind and still represents a formidable challenge. For example, the first C–H borylation of ferrocenes has been reported as early as 2004, but so far, its stereoselective variants remains elusive. In this paper, we hitherto disclose the first example of amide-directed Ir-catalyzed enantioselective dual C–H borylation of ferrocenes enabled by a chiral bidentate boryl ligand ( CBL ) (Scheme C).…”

Electrophilic C–H Borylation of Aza[5]helicenes Leading to Bowl-Shaped Quasi-[7]Circulenes with Switchable Dynamics

“…The compound reveals the lowest oxidation potential with an irreversible oxidation (E ox ) at +0.03 V, that may be ascribed to the oxidation of 1,8-diaminonaphthalene (E ox = +0.6 V vs Ag/AgCl, peak potential). 29 The HOMO−LUMO gaps (E g CV , Table 4.1, SI) calculated from the DPV or SWV measurements do not vary much within the set of the bowl-shaped compounds except for Bdan derivative 2g, for which the HOMO level was raised significantly, thereby decreasing E g CV to 1.97 V.…”