Photocatalytic oxidation of benzene to phenol using dioxygen as an oxygen source and water as an electron source in the presence of a cobalt catalyst

Abstract

The present study reports the first example of photocatalytic hydroxylation of benzene with O2 and H2O, both of which are the most green reagents, under visible light irradiation to afford a high turnover number.

Solar‐Driven Production of Hydrogen Peroxide from Water and Dioxygen

“…[50][51][52][53][54][55][56][57][58][59][207][208][209][210] The solar-driven productiono fH 2 O 2 from H 2 Oa nd O 2 may also be combined with an umber of green catalytic oxidationr eactions in which substrates are oxidized using O 2 ,w hich is the greenest oxidant. [211,212] Thus, H 2 O 2 is ap romising solar fuel as well as the green oxidant, which can be easily stored and carried, for personal use as well as af uel powerstation in future.…”

Photocatalytic Oxygenation Reactions Using Water and Dioxygen

“…[58] The photocatalytic oxygenation is started by photoinduced ET from [Ru(bpy) 3 [58] The quantum yield for the formationo fp-styrene oxide sulfonate in thep hotocatalytic oxygenation of p-styrene sulfonate with [(TMPS)Mn III (OH)] increased with increasing [Co III (NH 3 ) 5 Cl] 2 + concentration to reach ac onstantv alue close to 50 %, which corresponds to the maximum value for the one-photon one-electronprocess in Scheme 2. [62] The [Co III (NH 3 ) 5 [64,65] In the presence of benzene, benzene is hydroxylated with H 2 O 2 by redox catalysis of [Co III (Cp*)(bpy)(H 2 O)] 2 + to yield phenol. [60,61] The iron(III) complex of biuret-modified tetraamidomacrocyclic ligand (bTAML) also acts as an oxygenation catalyst in the photocatalytic hydroxylation and epoxidation of alkanes and alkenes, respectively, by using [Ru II (bpy) 3 5 Cl] 2 + as aw eak electron acceptor,a nd H 2 Oa sa n oxygen source (Scheme 4).…”

“…[58] An onheme iron(IV)-oxo complex, [59] Photocatalytic oxygenation of thioanisole to sulfoxide was also accomplished by using trinuclear Ru complexes as ap hotocatalyst as well as an oxygenation catalyst, H 2 Oa sa no xygen source,a nd [Co III (NH 3 ) 5 Cl] 2 + as an electron acceptor. [64] In the prolonged photoirradiation, the oxygen atom in phenol comesf rom H 2 O, because H 2 Oi so xidized to O 2 under the photocatalytic conditions (Scheme 5). [62] Photocatalytic oxidation of cis-1,2-dimethylcyclohexane and adamantane was performed in a mixture of CH 3 CN and H 2 18 O( 3:2 v/v)t oa fford > 90 %a nd > 95 %i ncorporation of 18 O-labeled oxygen atoms in 1-adamantanol and (1S,2R or 1R,2S)-1,2-dimethylcyclohexanol, respectively.…”

“…[60,61] The iron(III) complex of biuret-modified tetraamidomacrocyclic ligand (bTAML) also acts as an oxygenation catalyst in the photocatalytic hydroxylation and epoxidation of alkanes and alkenes, respectively, by using [Ru II (bpy) 3 5 Cl] 2 + as aw eak electron acceptor,a nd H 2 Oa sa n oxygen source (Scheme 4). [64] Photocatalytic oxygenation of hexamethylbenzene (HMB) was carried out by using H 2 Oa sa no xygen source,O 2 as a two-electron oxidant,a nd [Co(TPP)] (TPP 2À = tetraphenylporphyrin dianion) as ap hotoredoxc atalystt oy ield pentamethylbenzyla lcohol (PMBÀCH 2 OH) and hydrogen peroxide (H 2 O 2 ) with at urnover number of over 6000. [62] The [Co III (NH 3 ) 5 [64,65] In the presence of benzene, benzene is hydroxylated with H 2 O 2 by redox catalysis of [Co III (Cp*)(bpy)(H 2 O)] 2 + to yield phenol.…”

“…Then, thioanisole was oxygenated by [Fe IV (O)(MePy 2 tacn)] 2 + to yield the sulfoxide, in which the oxygen atom comes from H 2 O [63]. Photocatalytic Hydroxylation of Substrates with Metal Complexes by using H 2 Oasan Oxygen Source and O 2 as an Oxidant Photocatalytic hydroxylation of benzene to phenol was carried out by using O 2 as an oxidant, [Ru II (Me 2 phen) 3 ] 2 + (Me 2 phen = 4,7-dimethyl-1,10-phenanthroline) as ap hotoredox catalyst, [Co III (Cp*)(bpy)(H 2 O)] 2 + (Cp* = h 5 -pentamethylcyclopentadienyl) as at hermalr edox catalyst for both water oxidationa nd benzene hydroxylation reactions, and H 2 Oa sa ne lectron source in the presence of Sc(NO 3 ) 3 (Scheme 5) [64]. Photocatalytic Hydroxylation of Substrates with Metal Complexes by using H 2 Oasan Oxygen Source and O 2 as an Oxidant Photocatalytic hydroxylation of benzene to phenol was carried out by using O 2 as an oxidant, [Ru II (Me 2 phen) 3 ] 2 + (Me 2 phen = 4,7-dimethyl-1,10-phenanthroline) as ap hotoredox catalyst, [Co III (Cp*)(bpy)(H 2 O)] 2 + (Cp* = h 5 -pentamethylcyclopentadienyl) as at hermalr edox catalyst for both water oxidationa nd benzene hydroxylation reactions, and H 2 Oa sa ne lectron source in the presence of Sc(NO 3 ) 3 (Scheme 5) [64].…”