Modified Flavins Permit Catalytic Reductive Cyclization

Key words

flavins - photoexcitation - reductive cyclization barbituric acids - single-electron reductants

Significance

Storch and co-workers report a novel class of reduced air-stable flavin photocatalysts that, upon photoexcitation, permit the catalytic reductive cyclization of barbituric acid derivates and, therefore, replace the rare-earth reductant SmI₂ previously used to achieve this transformation. By using a catalytic system consisting of the flavin photocatalyst, triethylamine, and cysteine as a hydrogen-atom donor, along with γ-terpinene as a superstoichiometric reductant, the bicyclic products could be obtained in poor to excellent yields.

Comment

Whereas reductive transformations are well known for DNA photolyase enzymes, molecular flavins have not been used previously to achieve this reactivity. By introducing an additional substituent in the 6-position, the authors found the corresponding flavins to be air-stable in their reduced form, opening up a plethora of possibilities for catalytic reductive transformations. We look forward to the synthetic potential of this novel concept being revealed, especially in the context of asymmetric catalysis.

Publication History

Article published online:
17 May 2022