Catellani-Inspired BN-Aromatic Expansion: A Versatile Tool toward π-Extended 1,2-Azaborines with Tunable...

Area of Science:

• Organic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• BN-isosterism offers a route to novel organic compounds by replacing carbon-carbon units with boron-nitrogen pairs.
• Synthesizing larger BN-containing polyaromatic cores remains challenging, limiting exploration of their properties.

Purpose of the Study:

• To develop a method for accessing diverse extended BN-embedded polyaromatic cores.
• To investigate the impact of BN-unit orientation on the photophysical properties of these novel compounds.

Main Methods:

• Utilized a multigram-scale synthesis of BN-naphthalene.
• Employed a Catellani-type arene extension reaction (using Pd(OAc)2/P(2-furyl)3 and norbornene).
• Synthesized BN-embedded benzo[c]phenanthridines, curved ring-fused derivatives, and benzofluorenones with varying BN-vector orientations.

Main Results:

• Successfully synthesized diverse extended BN-polyaromatic cores, including benzo[c]phenanthridines and benzofluorenones.
• Achieved control over both normal and inverse BN-vector orientations within the synthesized structures.
• Demonstrated a >10-fold enhancement in light-induced singlet oxygen generation for the "boron-up" benzofluorenone isomer compared to the inverted isomer.

Conclusions:

• The developed strategy provides access to extended BN-polyaromatic cores with tunable electronic properties.
• BN-mapping offers a powerful approach for electronically tuning optically responsive organic materials.
• The orientation of the BN moiety significantly impacts photophysical properties, particularly singlet oxygen generation.