Doctor of Philosophy (PhD)
Cycloparaphenyleneacetylene (CPPA) and cycloparaphenylene (CPP) are called carbon nanohoops; they are fully conjugated macrocycles with radially oriented aromatic groups. Though many syntheses of CPPA and CPP were reported, in the macrocyclization step, the yields were usually not satisfying, as the reactions were irreversible. Our group utilizes alkyne metathesis to address this problem. Chapter 1 provides backgrounds and an introduction to the carbon nanohoops and alkyne metathesis.
Chapter 2 details the synthesis of the CPP4A and CPP5A, with good macrocyclization yields via alkyne metathesis. This study showed the error-correction ability of alkyne metathesis, especially with nonsymmetric substrates. As expected, CPP4A and CPP5A were more air-stable than CPP3A. Computational study and characterization using NMR and UV-Vis spectroscopy showed that enlarging the ring size stabilized the nanohoops.
As reductive aromatization was causing issues with scalability in the synthesis of CPP4A and CPP5A, in Chapter 3, we decided to avoid reductive aromatization, and found an alternative route by combining Kawase’s method with alkyne metathesis. We successfully synthesized the CPPA-Me8 in 600 mg scale, achieving scalable synthesis of CPPA. X-ray crystallographic analysis of the CPPA-Me8 showed a unique conformation, and DFT calculation further investigated this.
The construction of various macrocycles can be achieved via alkyne metathesis, not just carbon nanohoops. In Chapter 4, we attempted to synthesize a series of cyclic cisoid diamides (CCD) based macrocycles with different methods including alkyne metathesis. Despite many challenges, we were still able to build several unique macrocycles and investigate their properties.
Zhou, Xin, "Synthesis of Carbon Nanohoops and Macrocycles via Alkyne Metathesis" (2022). LSU Doctoral Dissertations. 5977.
Available for download on Friday, October 24, 2025