Development of Heck and Desaturation Reactions Involving Novel Hybrid Palladium-Radical Intermediates
thesisposted on 08.02.2018, 00:00 by Marvin Parasram
The first part of the thesis focuses on the development of the first endo-selective Pd-catalyzed Heck reaction of iodomethylsilyl ethers of phenols and alkenols leading to valuable allylic silyloxycylces. Mechanistic studies revealed that the transformation operates via a novel hybrid Pd-radical process. Also, it was found that the silicon atom is crucial for the observed endo selectivity, and it also enables post-modification of the reaction products. The obtained allylic silyloxycylces were efficiently oxidized to form Z-1,5-alkenols, which highlights our protocol as a useful tool for a formal Z-hydroxymethylation of a broad range of alkenols. The second part of the thesis discloses the development of an unprecedented visible-light induced Pd-catalyzed remote desaturation of aliphatic alcohols. Our strategy involves the development of silicon tethers that allow for auxiliary-controlled α-/β-, β-/γ-, γ-/δ-, and δ-/ε- desaturation of alcohols leading to valuable alkenol building blocks. This work involves a new mechanistic approach for remote C–H functionalization involving hybrid Pd-radical intermediates, which possess both radical and Pd character that enables a radical hydrogen atom transfer (HAT) reaction and a Pd-involved β-hydride elimination event to occur. The latter feature of the mechanism results in desaturation of alcohols with superior degrees of regioselectivity compared to the state-of-the-art desaturation methods.