title: Radical-Radical Cyclization Cascades of Barbiturates Triggered by Electron-Transfer Reduction of Amide-Type Carbonyls.
abstract: Radical-radical cyclization cascades, triggered by single-electron transfer to amide-type carbonyls by SmI2-H2O, convert simple achiral barbiturates in one step to hemiaminal- or enamine-containing tricyclic scaffolds containing up to five contiguous stereocenters (including quaternary stereocenters). Furthermore, we describe the surprising beneficial effect of LiBr on the most challenging of the radical-radical cyclization cascades. An alternative fragmentation-radical cyclization sequence of related substrates allows access to bicyclic uracil derivatives. The radical-radical cyclization process constitutes the first example of a radical cascade involving ET reduction of the amide carbonyl. Products of the cascade can be readily manipulated to give highly unusual and medicinally relevant bi- and tricyclic barbiturates.
authors.affiliation: School of Chemistry, Oxford Road, University of Manchester , Manchester, M13 9PL, United Kingdom.
authors.forename: Huan-Ming
authors.initials: HM
authors.lastname: Huang
authors.affiliation: School of Chemistry, Oxford Road, University of Manchester , Manchester, M13 9PL, United Kingdom.
authors.forename: David J
authors.initials: DJ
authors.lastname: Procter