Development and application of decatungstate catalyzed C–H ¹⁸F- and ¹⁹F-fluorination, fluoroalkylation and beyond

Abstract

We describe our efforts to develop a decatungstate (DT)-catalyzed C–H 18F- and 19F-fluorination reaction, and the discovery and exploitation of electrostatic effects in DT catalysis for the synthesis of radiotracers for PET imaging.

Recent advances of decatungstate photocatalyst in HAT process

“…Both compounds have attracted a lot of attention for the purpose of photocatalytic C–H functionalization due to their remarkable photochemical activity. 16–23 In the 1980s Papaconstantinou 24 explored the use of decatungstate and other polyoxometalates as photocatalysts and dectungstate in particular was further investigated through pioneering work by Hill and co-workers 25 and later by Fagnoni, Ryu, Ravelli and other groups. 16–22 The decatungstate anion displays a broad-band absorption spectrum with a centre at 324 nm.…”

“…16–23 In the 1980s Papaconstantinou 24 explored the use of decatungstate and other polyoxometalates as photocatalysts and dectungstate in particular was further investigated through pioneering work by Hill and co-workers 25 and later by Fagnoni, Ryu, Ravelli and other groups. 16–22 The decatungstate anion displays a broad-band absorption spectrum with a centre at 324 nm. As the wavelength of incident light increases, the absorption signal steadily decreases and eventually disappears at 420 nm.…”

“…As the wavelength of incident light increases, the absorption signal steadily decreases and eventually disappears at 420 nm. 26 According to mechanistic studies done by Hill, 25,26 Tanielian 22 and others, 16–21 it has been suggested that, upon photoexcitation, an excited state ([W 10 O 32 ] 4− *) species generated via intramolecular O-to-W ligand to metal charge transfer (LMCT) rapidly (∼30 ps) declines to a reactive state termed wO (lifetime: 55 ± 20 ns) with a quantum yield of approximately 0.6 (Scheme 1b). 27 The wO species demonstrates partial radical character on the oxygen centre and a predicted redox potential E ( wO /[W 10 O 32 ] 5− ) of approximately +2.44 V in comparison to a saturated calomel electrode (SCE).…”

An iron-containing POM-based hybrid compound as a heterogeneous catalyst for one-step hydroxylation of benzene to phenol

“…37–39 And the organic nitrogen heterocyclic ligands make conjugated π electrons more active, thereby activating the C–H bond of the benzene ring. 40,41 Based on the above analysis, a POM-based hybrid compound {[Fe II (pyim) 2 (C 2 H 5 O)][Fe II (pyim) 2 (H 2 O)][PMo V 2 Mo VI 9 V IV 3 O 42 ]}·H 2 O ( Fe 2 -PMo 11 V 3 ) was synthesized via hydrothermal synthesis selecting pyim ligands and iron ions to modify the POM anion. Fe 2 -PMo 11 V 3 exhibits an isolated structure, in which two Fe-pyim fragments are attached to the [PMo 11 V 3 O 42 ] 3− anion with a bi-capping structure by the Fe–O bond.…”

Engineering the heterogeneous photocatalytic activity of crystalline decatungstate-based coordination polymers

“…1 DT in a solution containing organic substrates could be easily reduced with appearance of blue color when irradiated with UV light, which signified its potential to act as a promising photocatalyst. 2,3 Recently, the decatungstate anion has attracted growing attention due to its outstanding photocatalytic performance in various reactions, including activation of inert C(sp 3 )-H bonds via hydrogen atom transfer (HAT) or single electron transfer (SET), [4][5][6] oxidation of organic substrates, [7][8][9][10][11] degradation of organic pollutants, 12,13 etc. However, commonly used DT-based photocatalytic catalysts, such as (Bu 4 N) 4 [W 10 O 32 ] (TBADT) and Na 4 [W 10 O 32 ] (NaDT), were known to have a relatively low light harvesting efficiency.…”