Iron-Catalyzed C–C Single-Bond Cleavage of Alcohols

Abstract

An iron-catalyzed deconstruction/hydrogenation reaction of alcohols through C−C bond cleavage is developed through photocatalysis, to produce ketones or aldehydes as the products. Tertiary, secondary, and primary alcohols bearing a wide range of substituents are suitable substrates. Complex natural alcohols can also perform the transformation selectively. A investigation of the mechanism reveals a procedure that involves chlorine radical improved O−H homolysis, with the assistance of 2,4,6-collidine.

Iron-catalyzed deconstructive alkylation through chlorine radical induced C–C single bond cleavage under visible light

“…20 We found recently that an iron salt can generate alkoxy radicals from simple alcohols through a chlorine radicalinduced procedure. 21 Zeng also reported a novel LMCT procedure of an Fe-OR intermediate with cyclic alcohols recently. 22 However, both the alcohol and olefine substrates suffered from strict limitations.…”

Photoinduced Fe-catalyzed bromination and iodination of unstrained cyclic alcohols

“…A plausible mechanism was then proposed (Scheme 2). 6,20,22 The O-radical Int-O formation from the free alcohol 1a was the first step. The ligand-to-metal charge transfer (LMCT) of the Int-Fe species or the homolysis of the Int-Br species would result in the formation of such an O-radical.…”

Synthetic Applications of Photocatalyzed Halogen‐Radical Mediated Hydrogen Atom Transfer for C−H Bond Functionalization

“…also used to activate OÀ H bonds in alcohols and carboxylic acids. [43,44] Given the above, the covered examples can be classified into three categories depending on the operating mechanism: photolysis triggered by Ligand-to-Metal Charge Transfer (LMCT), photoredox catalyzed outer-sphere single-electron transfer and energy transfer (Scheme 2).…”

“…[71] In another instance, the Hu group reported the generation of Cl * to promote the CÀ C bond cleavage via β-scission of an oxyl radical. [44] In this case, Cl * is used to cleave an OÀ H bond to afford the O-centered radical that undergoes β-scission.…”

“…Finally, we did not consider those cases where one of the substrates also works as the photocatalyst, [42] as these should be more properly referred to as photochemical approaches. It is worth mentioning that halogen radical‐mediated HAT has been also used to activate O−H bonds in alcohols and carboxylic acids [43,44] …”