Thermodynamic Control Enables trans-Selective Isomerization of Vicinal Diols via Iridium Photocatalysis

Key words

iridium catalysis - photocatalysis - diols - thermodynamic control - trans selectivity

Significance

The Wendlandt group reports a ­selective catalytic isomerization of cis-1,2-diols to trans-diequitorial-1,2-diols via photoredox catalysis. The use of Ph₃SiSH was found to be essential, as the nature of the silanethiol catalyst influenced the product distribution of the two isomers. The reaction was amenable to a variety of 1,2-diols and as well as mixtures of diastereomers, giving a single product isomer.

Comment

A series of mechanistic experiments revealed that, under the optimal conditions, the H-atom abstraction and donation steps were mediated by the Ph₃SiSH catalyst. The amine additive served as a base, not as a H-atom abstractor. The authors conclude that since the H-atom abstraction process is reversible, the equilibrium ratio represents the thermodynamic product distribution of the isomers.

Publication History

Article published online:
16 February 2022