Cerium-photocatalyzed aerobic oxidation of benzylic alcohols to aldehydes and ketones

Abstract

We have developed a cerium-photocatalyzed aerobic oxidation of primary and secondary benzylic alcohols to aldehydes and ketones using inexpensive CeCl3·7H2O as photocatalyst and air oxygen as the terminal oxidant.

Light-mediated aerobic oxidation of C(sp3)–H bonds by a Ce(iv) hexachloride complex

“…It was proposed that chlorine radical (Cl˙) was responsible for the C(sp 3 )–H bond cleavage, 41–49 consistent with recent work from our group, where the generation of Cl˙ radicals was demonstrated as the rate-limiting step, and the Cl˙ reactivity could be altered by the addition of suitable additives (alcohols and arenes). 50 The oxygenation of gaseous alkanes ( i.e.…”

“…It was proposed that chlorine radical (Cl • ) was responsible for the C(sp 3 )-H bond cleavage, [41][42][43][44][45][46][47][48][49] consistent with recent work from our group, where the generation of Cl • radicals was demonstrated as the rate-limiting step, and the Cl • reactivity could be altered by the addition of suitable additives (alcohols and arenes). 50 The oxygenation of gaseous alkanes (i.e., CH 4 and C 2 H 6 ) mediated by [NEt 4 ] 2 [Ce IV Cl 6 ] was studied with the goal of transformation of light alkanes into liquid fuels under mild conditions, in contrast with ceria based catalysts that employ harsh conditions.…”

Emergence of ligand-to-metal charge transfer in homogeneous photocatalysis and photosensitization

“…93 However, the Ce III photocatalysis has been thoroughly reviewed by Schelter elsewhere 94,95 and will not be covered here. Instead, we focus on the latest research on LMCT-enabled Ce IV photocatalysis, which has been led by Zuo, [96][97][98][99][100][101][102][103] Schelter, 104 König, [105][106][107] and Mashima 108, 109 over the past five years. Ce IV complexes are intrinsically powerful oxidants with redox potentials reaching as high as +1.63 V versus the standard calomel electrode for Ce(ClO4)3 under strongly acidic conditions.…”

{Ru(C6H6)}‐Decorating Heteropolymolybdate for Highly Activity Photocatalytic Oxidation of Benzyl Alcohol to Benzaldehyde

“…Besides, the fluorescence quenching experiments verified that the electron transfer occurred between the excited state of the POM and O 2 (Figure 4b), which was acoordance with the electron paramagnetic resonance (EPR) results (Figure S15) (EPR results demonstrated that the characteristic peaks of O 2 *À were observed under illumination, further confirming that O 2 *À was indeed formed during the reaction process). [54] Finally, no significant change in yield and selectivity was detected upon the addition of 2, 2, 6, 6-tetramethylpiperidine-N-oxyl (TEMPO) or isopropanol (IPA) to the reaction system, signifying 1 O 2 and OH * were not active species in this catalytic system. [55,56] Based on the literature reports and the above analysis, we proposed the mechanism of photocatalytic oxidation reaction of benzyl alcohol by compound 1 with the assitance of CAN and O 2 , [57][58][59][60] as shown in Scheme 1.…”