Visible-Light-Promoted Access to Fused Aza-Heterocyclic Frameworks

Area of Science:

• Organic Chemistry
• Sustainable Synthesis
• Photochemistry

Background:

• Growing demand for environmentally benign synthetic methods in organic chemistry.
• Visible light photochemistry offers an attractive, sustainable energy source.
• Diazo compounds are versatile reagents suitable for photochemical activation.

Purpose of the Study:

• To develop generalized photochemical pathways for synthesizing benzene-fused 1,4- and 1,3-diazines.
• To explore photocatalyst-free annulation reactions using diazo compounds.
• To investigate the construction of 5-membered aza-heterocyclic cores and late-stage modifications.

Main Methods:

• Visible light irradiation of diazo compounds with aza bis-nucleophiles in water.
• Direct photoinduced carbene generation without a photocatalyst.
• Control experiments and Density Functional Theory (DFT) studies for mechanistic insights.

Main Results:

• Successful synthesis of benzene-fused 1,4- and 1,3-diazines via [4+2] or [5+1] annulation pathways.
• Formation of 5-membered aza-heterocyclic cores using the same photochemical approach.
• Generation of diverse spiroindene compounds and steroid-embedded diaza heterocycles through late-stage C-H activation.

Conclusions:

• Developed a novel, sustainable, and photocatalyst-free method for synthesizing diverse nitrogen-containing heterocycles.
• Demonstrated the versatility of visible light-mediated diazo chemistry in organic synthesis.
• Provided a new strategy for constructing complex molecular architectures, including those relevant to medicinal chemistry.