Date of Award
Doctor of Philosophy
Aaron D. Sadow
The research presented and discussed in this dissertation involves the synthesis of aromatic dicarboxylates via catalytic isomerization or disproportionation, the synthesis of amines via catalytic hydrosilylation of amides and the development of new methods and approaches for studying catalytic reactions on an automated synthesis platform. The automated synthesis platform was utilized for studying kinetics of oxidation reactions of cyclohexane, as well as the synthesis of small molecules in specialized reactors and scalable quantities of heterogeneous catalysts.
Aromatic dicarboxylic acids such as terephthalic acid or 2,5-furandicarboxylic acid can be prepared through catalytic disproportionation or isomerization of their respective metal carboxylate precursors. Copper(I) iodide catalyzes the disproportionation of potassium furoate to 2,5-furandicarboxylate in up to 85% yield at temperatures of 280 – 300 °C under a carbon dioxide rich atmosphere (40 bar). CuI also catalyzes the disproportionation of potassium benzoate to terephthalate in up to 60% yield at temperatures of 320 – 350 °C under carbon dioxide (40 bar).
XantphosRh(cod)BArF (cod = 1,5-cyclooctadiene; BArF = Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) was demonstrated to be an excellent catalyst for the reduction of secondary and tertiary amides to secondary and tertiary amines by phenylsilane. Most substrates could be converted at mild temperatures (25 – 60 °C) within 1 h. Tertiary amides required 2 equiv. of PhSiH3 for full conversion. Secondary amides exhibited side reactions involving disproportionation of N-R and N-H bonds. These side reactions were inhibited by the addition of 10 equiv. of PhSiH3.
An automated synthesis robot (Chemspeed SWING-XL) was used to prepare surface supported catalysts of Pd on CeO2, SiO2, TiO2 for hydrogenation reactions. These materials were prepared by iterative additions of a dilute pre-catalyst solution followed by slow evaporation of solvent. These materials were used as catalysts for hydrogenolysis experiments, affording cyclohexanol from guaiacol. This instrument was also used to study the kinetics of cyclohexane oxidation reactions catalyzed by a series [tris(oxazolinyl)borato]cobalt compounds previously reported in our group. Finally, this same instrument was used to prepare synthetically challenging diene compounds, by slowly adding catalyst to a heated, pressurized reactor using high-pressure peristaltic pumps.
Zachary Benjamin Weinstein
Weinstein, Zachary Benjamin, "Synthesis of aromatic dicarboxylates and unique approaches to automated synthesis" (2018). Graduate Theses and Dissertations. 17355.