Mild and Selective C(CO)–C(α) Bond Cleavage of Ketones by Rhodium(III) Porphyrins: Scope and Mechanism

Rhodium­(III) porphyrins were found to undergo selective
C­(CO)–C­(α)
bond activation (CCA) of ketones promoted by water at temperatures
as low as 50 °C. The acyl group of the ketone was transferred
to the rhodium center, and the alkyl fragment was oxidized to a carbonyl
moiety accordingly. The hydroxyl group of water is transferred to
the rhodium porphyrin through hydrolysis of the kinetic α-carbon–hydrogen
bond activation (α-CHA) product to give RhIII(ttp)­OH
(ttp = 5,10,15,20-tetratolylporphyrinato dianion), which subsequently
cleaves the C­(CO)–C­(α) bond of ketone.