In the field of synthetic chemistry, oximes are crucial nitrogen-containing compounds widely used as synthetic precursors in the development of pharmaceuticals and functional materials. Notably, the homolytic cleavage of the N-O bond to generate imine radicals has emerged as a key strategy for oxime transformation. 

However, unactivated oximes are often prone to side reactions, which complicates the selective cleavage of the N–OH bond. As a result, most studies to date have focused on activated oximes such as oxime esters or ethers.

A study published in Angewandte Chemie International Edition and conducted by a research team led by Prof. SU Weiping and Prof. JIE Xiaoming from the Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences focused on developing radical-based reactions for the transformation of inert bonds, and opened up an efficient and universal synthetic route for the direct transformation of unactivated oximes.

The researchers achieved the direct cyclization of unactivated oximes with α,β-unsaturated aldehydes under green light-induced copper and photocatalytic synergistic conditions. This reaction produced only water as a byproduct, offering a novel and efficient route for the rapid construction of pyridine frameworks.

Under the optimal reaction conditions, the researchers conducted an in-depth study on the substrate scope. Experimental results indicated that, due to the mild conditions, the reaction demonstrated good tolerance toward most common functional groups, and substrates with more complex structures could also undergo the desired transformation.

To further reveal the practical value of this reaction, the researchers applied this synthetic strategy to the construction of various conjugated pyridine derivatives containing electron-donating units and investigated their photoluminescent properties. They found that some of the products exhibited significant solvatochromic effects, providing strong support for the development of functional materials.

The reaction provides a concise and environmentally friendly synthesis method for constructing functionally dense, multi-substituted pyridine compounds. Through the synergistic effect of the dual-catalysis system, the method not only eliminates the need for activation group introduction, a common step in traditional approaches, but also broadens the application scope of oxime compounds in synthetic chemistry.