Abstract by Garrison Nickel
Chemistry and Biochemistry
Microwave-promoted radical cyclizations of oxime ethers
The cyclization of iminyl radicals is a powerful process for creating dihydropyrroles and pyrroles. Iminyl radicals are formed upon microwave heating of O-phenyl oxime ethers, eliminating the need for heavy metal, peroxide, or photoredox catalysts. These iminyl radicals cyclize via a 5-exo-trig process and can be captured after cyclization by a variety of radical traps. This results directly in the synthesis of many functionalized adducts via a radical cascade process. We demonstrate the use of various radical traps in the formation of new bonds between the exo-carbon and carbon, oxygen, sulfur, nitrogen, and halogens. Additionally, we demonstrate that installing a thiophenyl group as a radical acceptor on the carbon beta to the cyclization site allows for iminyl radical cyclizations to proceed without addition of an external radical trap, resulting in a vinyl dihydropyrrole species.