CONTROLLING ARCHITECTURE USING C2-SYMMETRIC CATALYSTS: FROM SMALL MOLECULES TO LARGE POLYMERS

Abstract

My doctoral studies have concentrated on the use of C2-symmetic catalysts to control the three-dimensional construction of molecules. The first half of my thesis focuses on asymmetric addition of phenols into Pd π-allyl complexes. This work was inspired by the natural product, sch202596, an antagonist for the galinin receptor that contains a highly stereogenic and compact carbasurgar structure appended onto a phenol by an allylic aryl-ether bond. A transformation was developed in which racemic allylic oxides underwent a Tsuji-Trost reaction to give diastereomeric π-allyl complexes. Addition of a nucleophile resulted in enantioenriched regioisomers in good yields. We termed this approach allylic oxide regio resolution (AORR). Using this approach, four different carbasurgar natural products were synthesized: streptol, MK7607, cyathiformine B and polyporapyranone G. Additionally, this method was extended to append carbasugar-like molecules onto complex natural products. Furthermore, C2-symmetic catalysts were used to synthesize polymers with stereoregularity, which will be the focus of the second half of my thesis. Utilizing advances in chain walking polymerization, 1-butene was polymerized resulting in a novel isotactic semi-crystalline polymer. The ligand framework and reaction conditions were probed in order to optimized the system, which gave an active catalyst that produced a polymer with few stereo and regioerros. Specifically, it was found that ortho-cumyl groups were necessary to maintain the stereochemical information through the chain walking steps. Additionally reaction conditions were explored and discovered that a reaction temperature of −40 °C and a concentration of approximately 8 M were the optimal conditions. Finally, the use of non-aromatic, high polarity, aprotic solvents proved beneficial.