Chemistry and Biochemistry
Bayer School of Natural and Environmental Sciences
catalysis, atom transfer radical addition, transfer hydrogenation, amide conformation, green chemistry, step-growth polymerization, Thorpe Ingold
This work focused on “greening” catalytic processes, atom transfer radical addition (ATRA), which adds an alkyl halide across and alkene, and transfer hydrogenation/dehydrogenation, which reduces a carbonyl without needing direct H2 gas. Part of “greening” of these processes is through using abundant first row metals, Cu and Ni for catalysis. One aim was to design new ligands which would be more active in these systems; the second was investigation of additives for catalyst regeneration to reduce the catalyst loading necessary for high yields.
The TPMA* family was investigated in ATRA. Rate constants followed the expected trend, which increased with increasing electron-donation, but ATRA reactions yielded the opposite. Expected trends were yielded utilizing acetone, showing halidophilicity was an important factor. [Cu(Me6TREN)Cl][Cl] was investigated using ascorbic acid ATRA, and found catalyst protonation. Adding small amounts of base improved yields by >80%. Coordination studies concluded base was not displacing the inner sphere halogen essential for radical deactivation.
Photo-initiated ATRA methods were studied, and conditions utilized to synthesize sequence-regular macromonomers for step-growth polymerization. Degrees of polymerization were less than 10. XRD analysis of crystals grown from a crude reaction mixture found a cyclized dimer.
Cascade ATRC was explored as a way to synthesize g-lactones. Having geminal-dialkyl substituents was necessary due to the Thorpe Ingold effect. Computational studies agreed well with experiment.
Conformational studies found 3˚ amides preferred the cis conformation over trans mostly due to steric strain between the a-substituent N-Me, and rotation out of plane is due to sterics and unfavorable electrostatic interactions.
Unique pyridyl-monoprotic aminophosphines (MAPs) were synthesized with phenyl or tert-butyl phosphines and coordinated to nickel. Computationally, P-bound complexes were more stable than N-bound by ~12 kcal/mol, and nickel preferred to be low spin.
This work provided a significant contribution to several fields: ATRA/ATRC, amide synthesis, and transfer hydrogenation. Ligand development and reaction optimization provided greener methods by lowering catalyst loading necessary for product formation, and fundamental understanding of structure and function relationships for diene esters, amides, and Ni-MAP complexes was achieved.
Pros, G. (2019). Greening of Catalytic Processes Using First-Row Transition Metals for Atom Transfer Radical Addition and Transfer Hydrogenation (Doctoral dissertation, Duquesne University). Retrieved from https://dsc.duq.edu/etd/1828
Available for download on Sunday, December 20, 2020