C-C Coupling in sterically demanding porphyrin environments.

Area of Science:

• Organic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Classic synthetic protocols for C-C bond forming reactions on nonplanar porphyrins are underdeveloped.
• Nonplanar porphyrin architectures are crucial for applications in supramolecular assemblies, catalysis, and sensing.
• Developing efficient synthetic routes is key to advancing porphyrin chemistry.

Purpose of the Study:

• To synthesize a library of arm-extended dodecasubstituted porphyrins.
• To optimize the Suzuki-Miyaura coupling for functionalizing sterically demanding, nonplanar porphyrins.
• To explore C-C bond formation at different meso-phenyl positions (ortho, meta, para).

Main Methods:

• Optimization of the Suzuki-Miyaura coupling reaction.
• Palladium-catalyzed cross-coupling of peripheral haloaryl substituents with boronic acids.
• Borylation of dodecasubstituted porphyrin's meso-phenyl position.
• X-ray crystallography for structural analysis.

Main Results:

• Successfully synthesized arm-extended dodecasubstituted porphyrins.
• Achieved C-C bond formation at the para- and meta-meso-phenyl positions.
• Ortho-functionalization at the meso-phenyl position proved elusive for these sterically hindered systems.
• Reversing the polarity of the reaction via borylation and subsequent coupling led to higher yields.
• X-ray analysis confirmed the formation of supramolecular assemblies with substrate-accommodating voids.

Conclusions:

• The optimized Suzuki-Miyaura coupling is effective for meta- and para-functionalization of dodecasubstituted nonplanar porphyrins.
• Ortho-functionalization remains a synthetic challenge for these sterically demanding porphyrins.
• The developed synthetic strategies yield porphyrins capable of forming supramolecular assemblies, opening avenues for new applications in catalysis and sensing.