1076691-75-2Relevant academic research and scientific papers
Unique diastereoselectivity trends in aminyl radical cyclizations onto silyl enol ethers
Zlotorzynska, Maria,Zhai, Huimin,Sammis, Glenn M.
supporting information; experimental part, p. 864 - 872 (2010/05/18)
(Chemical Equation Presented) The cyclization of nitrogen-centered radicals onto silyl enol ethers is an efficient method for the synthesis of polyhydroxylated alkaloids as the 2-hydroxymethylpyrrolidine core can be readily accessed from a linear precursor. During our studies on the synthesis of polyhydroxylated alkaloid CYB-3, we found that the diastereoselectivity of the cyclization was dependent on a complex combination of sterics and olefin geometry. A more thorough understanding of the factors that lead to high diastereoselectivites would greatly expand the utility of this methodology in complex natural product synthesis. We have found that cyclization diastereoselectivities of substrates with alkyl or aryl substitution were excellent regardless of olefin geometry or substitution pattern. When electronegative substituents were introduced adjacent to the silyl enol ether, only Z-silyl enol ethers provide high diastereoselectivites. Temperature, steric size of the silyl group, and sterics and electronics of the metal hydride affected the selectivity to a lesser extent.
Chemoselective oxygen-centered radical cyclizations onto silyl enol ethers
Zlotorzynska, Maria,Zhai, Huimin,Sammis, Glenn M.
supporting information; experimental part, p. 5083 - 5086 (2009/05/31)
(Chemical Equation Presented) A new oxygen-centered radical cyclization onto silyl enol ethers has been developed and utilized for the synthesis of versatile siloxy-substituted tetrahydrofurans. The reactions display excellent chemoselectivity for cyclization onto the electron-rich silyl enol ether when competing terminal alkene cyclization, 1,5-hydrogen abstraction, and β-fragmentation pathways are present. The increased chemoselectivity also allows for the synthesis of tetrahydropyrans, a challenging substrate class to access using oxygen-centered radical alkene cyclizations due to competing 1, 5-hydrogen abstractions.
