Pd-Catalyzed Cross Coupling Strategy for Functional Porphyrin Arrays

Abstract

Porphyrin arrays are an important class of compounds to study interporphyrin electronic interactions that are crucial in determining the rates of energy transfer and electron transfer reactions. When the electronic interactions become stronger, porphyrin arrays exhibit significantly altered optical and electronic properties owing to large oscillator strength and flexible electronic nature of porphyrins. In addition, porphyrins accept various metal cation in their cavities and the interporphyrin interactions depend upon the coordinated metal. With these in the background, porphyrin arrays have been extensively explored as sensors, multielectron catalysts, photodynamic therapy reagents, artificial photosynthetic antenna, nonlinear optical materials, and so on. Here, we review the synthesis of porphyrin arrays by palladium-catalyzed cross-coupling reactions, which are quite effective to construct carbon-carbon bonds and carbon-nitrogen bonds in porphyrin substrates. Palladium-catalyzed cross coupling reactions employed so far are Suzuki-Miyaura coupling reaction, Sonogashira coupling reaction, Buchwald-Hartwig amination, Mizoroki-Heck reaction, Migita-Kosugi-Stille coupling reaction, and so on. In each case, the representative examples and synthetic advantages are discussed.

Scheme 1. Synthesis of meso–meso Directly Linked Porphyrin Arrays

Scheme 2. Synthesis of β–β and β–meso Directly Linked Porphyrin Arrays

Scheme 3. Synthesis of meso–meso 2,5-Pyrrolyene Bridged Linear Porphyrin Arrays

Reagents and conditions: a) Pd₂(dba)₃, PPh₃, CsF, Cs₂CO₃, toluene, DMF, reflux; b) p-xylene, reflux

Scheme 4. Synthesis of meso–meso Directly Linked Cyclic Porphyrin Arrays

Scheme 5. Synthesis of meso–β Directly Linked Cyclic Porphyrin Arrays

Scheme 6. Synthesis of meso–β Directly Linked Cyclic Porphyrin Arrays

Scheme 7. Synthesis of β–β Directly Linked Cyclic Porphyrin Arrays

Scheme 8. Synthesis of meso–meso Spacer Bridged Cyclic Porphyrin Arrays

Scheme 9. Synthesis of Thienylene- and Pyrrolylene-Bridged Cyclic Porphyrin Arrays

Scheme 10. Synthesis of β–β Thienylene-Bridged Cyclic Porphyrin Arrays

Scheme 11. Synthesis of β–β Pyridylene-Bridged Cyclic Porphyrin Arrays

Scheme 12. Synthesis of β–β Pyridylene-Bridged Dimer 63 and Trimer 64

Scheme 13. Synthesis of β–β Pyridiylene-Bridged Cyclic Porphyrin Arrays (Nano-Porphyrin Barrel)

Scheme 14. Synthesis of β–β and meso–meso Azobenzene-Bridged Cyclic Porphyrin Arrays

Scheme 15. Synthesis of Azobenzene-Bridged Porphyrin–Dipyrrin Dimers

Scheme 16. Synthesis of Diethynylphenylene-Bridged Porphyrin Dimers

Scheme 17. Synthesis of meso–meso Acetylene-Bridged Porphyrin Oligomers

Scheme 18. Synthesis of β–β Acetylene-Bridged 5,15-Diazaporphyrin Dimer

Scheme 19. Synthesis of meso–meso Diphenylethynyl-Bridged Cyclic Porphyrin Arrays

Scheme 20. Synthesis of meso–meso Acetylene-Bridged Porphyrin Nanorings

Scheme 21. Synthesis of meso–meso Nitrogen-Bridged Diporphyrinylamine

Scheme 22. Synthesis of β–meso and β–β Nitrogen-Bridged Diporphyrinylamine

Scheme 23. Synthesis of 1,3,5-tris(Zn(II)-porphyrinylamino)benzene and Triaminyl Radical

Scheme 24. Synthesis of meso–β Ethenylene-Bridged Dimer

Scheme 25. Synthesis of Di(vinylphenyl)porphyrin Polymers

Scheme 26. Synthesis of β–β-Vinylbenzene-Bridged Porphyrin Oligomers

Scheme 27. Synthesis of meso–meso (E)-Vinylene-Bridged Porphyrin Dimer

Scheme 28. Synthesis of Pyrrole- and Thiophene-Bridged 5,15-Diazaporphyrin Dimers

Scheme 29. Synthesis of Triphenylene-Linked Diporphyrin