Combining Sanford Arylations on Benzodiazepines with the Nuisance Effect

Area of Science:

• Organic Chemistry
• Catalysis
• Medicinal Chemistry

Background:

• Benzodiazepines are important pharmaceutical scaffolds.
• Developing efficient synthetic methods for functionalizing benzodiazepines is crucial for drug discovery.
• Palladium catalysis offers powerful tools for C-C bond formation.

Purpose of the Study:

• To develop a novel palladium- and photoredox-catalyzed method for the synthesis of 5-(2-arylphenyl) benzodiazepine analogues.
• To investigate the reaction mechanism and compare it with palladium-only catalysis.
• To explore the scope and limitations of the new synthetic strategy.

Main Methods:

• Utilizing palladium and visible light photoredox catalysis for the reaction of 5-phenyl-1,3-dihydro-2H-1,4-benzodiazepin-2-ones with aryldiazonium salts in methanol.
• Employing Density Functional Theory (DFT) for computational mechanistic analysis.
• Characterizing the resulting products using standard spectroscopic techniques.

Main Results:

• The reaction successfully afforded the desired 5-(2-arylphenyl) benzodiazepine analogues.
• A "nuisance effect" was observed with fluorobenzenediazonium derivatives, leading to both fluoroaryl and methoxyaryl products.
• DFT analysis revealed that photocatalysis facilitates a lower-energy single-electron transfer (SET) pathway compared to palladium-only catalysis, which involves a high-energy oxidative addition step.

Conclusions:

• A novel and efficient palladium- and photoredox-catalyzed method for synthesizing functionalized benzodiazepines has been established.
• The study elucidates the mechanistic differences between photoredox and traditional palladium catalysis in this transformation.
• The findings provide valuable insights into the development of new catalytic strategies for complex molecule synthesis.