Date of Award
Doctor of Philosophy
Levi M. Stanley
In this thesis, various palladium-catalyzed reactions to form C-N and C-C are discussed. These reactions span N-tert-prenylation, conjugate addition of arylboronic acids to β,β-disubstituted enones and Suzuki-Miyaura cross-coupling of haloarenes and arylboronic acids.
Palladium-catalyzed conjugate addition of wide range of arylboronic acids to β,β-disubstituted enones occur to form ketone products bearing benzylic all-carbon quaternary centers. A simple catalyst prepared from palladium trifluoroacetate and 2,2ʹ-bipyridine promotes these reactions. The use of aqueous sodium trifluoroacetate as the reaction medium significantly enhances reactivity and enables formation of challenging bis-benzylic and ortho-substituted benzylic all-carbon quaternary centers.
Palladium(II)-functionalized MOF-253 (MOF-253-Pd(OAc)2) can be used as a recyclable catalyst to form all-carbon quaternary centers via conjugate additions of arylboronic acids to β,β-disubstituted enones in aqueous media. MOF-253-Pd(OAc)2 can be reused 8 times to form ketone products in high yields and PXRD confirms the crystallinity remains intact. Additions of a range of stereoelectronically diverse arylboronic acids to a variety of β,β-disubstituted enones catalyzed by MOF-253-Pd(OAc)2 occur in modest-to-high yields.
The electronic and steric effects of linker substitution on the activity of metalated MOFs have been investigated in the context of Suzuki–Miyaura cross-coupling reactions. m-6,6ÃÂ´-Me2bpy-MOF-PdCl2 (UiO-67-Pd-6,6ÃÂ´-dimethyl-bpydc0.4/bpdc0.6) exhibited a remarkable enhancement in the activity compared to non-functionalized m-bpy-MOF-PdCl2 (UiO-67-Pd-bpydc0.5/bpdc0.5) and m-4,4ÃÂ´-Me2bpy-MOF-PdCl2(UiO-67-Pd-4,4ÃÂ´-dimethyl-bpydc0.4/bpdc0.6). This result clearly demonstrates that the stereoelectronic properties of metal-binding linker units are critical to the activity of single-site organometallic catalysts in MOFs.
Three distinct protocols are developed for the synthesis of N-tert-prenylindoles using indole, (η6-indole)Cr(CO)3, and indoline nucleophiles in the presence of the same catalyst generated from [Pd(η3-prenyl)Cl]2 and Xantphos. These reactions form N-tert-prenylindole products with a broad range of substitution and electronic character in high yields with high tert-prenyl-to-n-prenyl selectivity.
Ryan Van Zeeland
Van Zeeland, Ryan, "Exploring Palladium Catalysis: From N-tert-prenylation to green chemistry" (2016). Graduate Theses and Dissertations. 15830.