Metallaphotoredox Enabled Single Carbon Atom Insertion into Alkenes for Allene Synthesis

Area of Science:

• Organic Chemistry
• Catalysis
• Photochemistry

Background:

• Synthesizing allenes efficiently from simple precursors remains a significant challenge in organic chemistry.
• Existing methods, like the Doering-LaFlamme reaction, have limitations.
• Development of novel synthetic strategies is crucial for accessing diverse allene structures.

Purpose of the Study:

• To introduce a novel, efficient, and mild two-stage protocol for allene synthesis.
• To explore a photochemical rearrangement approach utilizing synergistic catalysis.
• To demonstrate the broad applicability of the developed method.

Main Methods:

• A two-stage synthesis protocol involving single-atom insertion into alkenes.
• Synergistic photoredox and cobalt catalysis.
• Radical-based photochemical rearrangement mechanism.
• Density functional theory (DFT) calculations for mechanistic insights.

Main Results:

• The protocol efficiently synthesizes allenes under mild conditions.
• Demonstrated broad substrate scope, including late-stage diversification of complex molecules.
• Mechanistic studies suggest a radical pathway via cyclopropyl carbene intermediates.

Conclusions:

• The presented photochemical rearrangement offers a powerful new tool for allene synthesis.
• The method is efficient, mild, and versatile, applicable to natural products and bioactive molecules.
• Understanding the radical mechanism provides a foundation for further synthetic development.