Eosin Y- and Copper-Catalyzed Dark Reaction To Construct Ene-γ-Lactams

Area of Science:

• Organic Chemistry
• Catalysis
• Photoredox Catalysis

Background:

• Eosin Y is a well-established organo-photocatalyst for visible-light photoredox reactions.
• Thermal redox reactions often require harsh conditions or specific catalysts.

Purpose of the Study:

• To explore the catalytic activity of Eosin Y in thermal redox reactions.
• To develop a novel synthetic method for lactam formation.
• To demonstrate Eosin Y-catalyzed reactions in the absence of light.

Main Methods:

• Utilized Eosin Y as a catalyst with a catalytic amount of Copper(II) acetate (Cu(OAc)₂).
• Investigated the reaction between vinyl azides and ketene silyl acetals.
• Performed reactions under thermal conditions, without light irradiation.

Main Results:

• Eosin Y exhibited excellent catalytic activity for thermal redox reactions.
• The reaction successfully formed formal [3 + 2] cycloadducts via α-ester radical addition.
• This represents the first reported instance of Eosin Y-catalyzed redox reactions occurring in the dark.

Conclusions:

• A mild and straightforward synthetic strategy for five-membered ene-γ-lactams and bridge ring lactams was established.
• This work expands the catalytic applications of Eosin Y beyond photoredox catalysis.
• The developed method offers a new pathway for synthesizing important lactam synthons.