Issue 20, 2023

Mechanistic studies on catalytic alkane oxidation by Murahashi's O2/copper(ii)/aldehyde system

Abstract

Mechanistic studies on catalytic alkane hydroxylation by Murahashi's O2/copper(II)/aldehyde system have been conducted to show that the autoxidation of an aldehyde (RCHO) by an O2 generating acyl radical intermediate (RC(O)˙) is involved as an initiation step of the catalytic cycle. The generated RC(O)˙ is trapped by O2 to give an acylperoxyl radical intermediate RC(O)OO˙, which may react with another RCHO to generate an adduct intermediate RC(O)OOC(R)(H)O˙. The following O–O bond homolytic cleavage of this intermediate will give acyloxyl intermediate RC(O)O˙ and RCOOH, in which the former acts as a reactive species for hydrogen atom abstraction (HAA) from alkane substrates (R1R2CH2; R1 and R2 are alkyl groups or hydrogen atoms), giving R1R2CH˙. The generated R1R2CH˙ reacts with O2 to generate alkylperoxyl radical intermediate R1R2CHOO˙, which then undergoes the Russell reaction to give R1R2CHOH (alcohol) and R1R2C[double bond, length as m-dash]O (ketone) in a 1 : 1 ratio as the oxidation products. The acyloxyl intermediate RC(O)O˙ also reacts with RCHO to give carboxylic acid RC(O)OH and RC(O)˙, constructing the catalytic cycle. The role of copper(II) ions in the above catalytic process is also investigated using a series of copper(II) complexes. Furthermore, Murahashi's system was adopted in the catalytic oxidation of methane.

Graphical abstract: Mechanistic studies on catalytic alkane oxidation by Murahashi's O2/copper(ii)/aldehyde system

Supplementary files

Article information

Article type
Paper
Submitted
07 Jul 2023
Accepted
18 Jul 2023
First published
25 Aug 2023

Catal. Sci. Technol., 2023,13, 5859-5867

Author version available

Mechanistic studies on catalytic alkane oxidation by Murahashi's O2/copper(II)/aldehyde system

K. Yamaguchi, Y. Uemura, H. Sugimoto, R. Ito, Y. Morimoto and S. Itoh, Catal. Sci. Technol., 2023, 13, 5859 DOI: 10.1039/D3CY00944K

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