Syntheses of donor-acceptor-functionalized dihydroazulenes

Area of Science:

• Organic Chemistry
• Materials Science
• Molecular Electronics

Background:

• The dihydroazulene (DHA)/vinylheptafulvene (VHF) photo/thermoswitch is key for advanced materials.
• Tuning its optical and switching properties requires novel derivatives.
• Previous studies highlighted the influence of donor/acceptor groups on isomer switching.

Purpose of the Study:

• To investigate the synthesis of substituted DHA derivatives.
• To explore functionalization of the DHA core and seven-membered ring.
• To optimize palladium-catalyzed coupling reactions for DHA derivatives.

Main Methods:

• A four-step synthesis of the DHA core from acetophenone and tropylium substrates.
• Introduction of diverse functional groups onto the phenyl unit of acetophenone.
• Regioselective bromination-elimination for seven-membered ring functionalization.
• Palladium-catalyzed cross-coupling reactions (cyanation, Sonogashira, Suzuki).

Main Results:

• A wide range of functional groups on acetophenone were tolerated, yielding substituted DHA derivatives.
• A regioselective protocol introduced a bromo substituent at position 7 of the DHA core.
• Optimized Suzuki coupling conditions were developed, minimizing azulene byproduct formation.
• Successful palladium-catalyzed cyanation, Sonogashira, and Cadiot-Chodkiewicz couplings were achieved.

Conclusions:

• Efficient synthetic strategies provide access to diverse DHA derivatives.
• These derivatives are valuable for fine-tuning DHA/VHF photo/thermoswitch properties.
• The developed methods facilitate the creation of new molecular electronic components.