Utilization of Natural Sunlight and Air in the Aerobic Oxidation of Benzyl Halides

Abstract

A novel, efficient oxidation of α-aryl halogen derivatives to the corresponding α-aryl carbonyl compounds at room temperature has been disclosed. Natural sunlight and air are successfully utilized in this approach through the combination of photocatalysis and organocatalysis. A plausible mechanism was proposed on the basis of the mechanistic studies.

DMSO/I2 mediated C–C bond cleavage of α-ketoaldehydes followed by C–O bond formation: a metal-free approach for one-pot esterification

“…To know the generality of iodine source for this reaction, some reagents were screened. As observed in 20 our initial experiments, the reaction in other solvents has not given the desired product; this shows the presence of DMSO is required to undergo the reaction. There was no product formation observed in all other cases (Table 1).…”

“…A reaction conducted without iodine did not 20 undergo. In a reaction of 2oxo-2-phenylacetaldehyde 1, with I 2 in catalytic amount and DMSO as solvent, the decarbonylative oxidation was observed 10 with the formation of benzoic acid 2a, in low yields (Scheme 1).…”

Visible Light Photoredox Catalysis with Transition Metal Complexes: Applications in Organic Synthesis

“…71 In their mechanistically unique strategy, a pyridine derivative serves to activate the α -haloester substrate and molecular oxygen serves as the terminal oxidant and source of the oxygen atom incorporated into the product. Thus, ethyl α -bromophenylacetate ( 92 ), which does not react in the absence of a pyridine catalyst, is converted in good yield into ethyl benzoylformate ( 93 ) in the presence of catalytic amounts of 4-methoxypyridine ( 94 ) and Ru(bpy) 3 2+ by running the reaction under air (Scheme 23).…”

Highly Efficient Aerobic Oxidative Hydroxylation of Arylboronic Acids: Photoredox Catalysis Using Visible Light

“…[11] Recently, the groups of Blechert and Wang [12] developed a metal-free photooxidative system to achieve the oxidation of amines and alcohols, and Jiao et al described the use of a Ru II polypyridine complex and 4-methoxypyridine to promote the conversion of a-aryl halogen derivatives into a-aryl carbonyl compounds. [13] The molecular oxygen in air has been widely used as a green oxidant in synthesis. [14] Consequently, the development of visible-light photooxidative reactions using air as the oxidant is highly desirable.…”