Highly Functionalized Cyclopentane Derivatives by Tandem Michael Addition/Radical Cyclization/Oxygenation Reactions.
Chemistry
; 21(27): 9877-88, 2015 Jun 26.
Article
en En
| MEDLINE
| ID: mdl-26012714
ABSTRACT
Densely functionalized cyclopentane derivatives with up to four consecutive stereocenters are assembled by a tandem Michael addition/single-electron transfer oxidation/radical cyclization/oxygenation strategy mediated by ferrocenium hexafluorophosphate, a recyclable, less toxic single-electron transfer oxidant. Ester enolates were coupled with α-benzylidene and α-alkylidene ß-dicarbonyl compounds with switchable diastereoselectivity. This pivotal steering element subsequently controls the diastereoselectivity of the radical cyclization step. The substitution pattern of the radical cyclization acceptor enables a switch of the cyclization mode from a 5-exo pattern for terminally substituted olefin units to a 6-endo mode for internally substituted acceptors. The oxidative anionic/radical strategy also allows efficient termination by oxygenation with the free radical 2,2,6,6-tetramethyl-1-piperidinoxyl, and two C-C bonds and one C-O bond are thus formed in the sequence. A stereochemical model is proposed that accounts for all of the experimental results and allows the prediction of the stereochemical outcome. Further transformations of the synthesized cyclopentanes are reported.
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1
Colección:
01-internacional
Base de datos:
MEDLINE
Tipo de estudio:
Prognostic_studies
Idioma:
En
Revista:
Chemistry
Asunto de la revista:
QUIMICA
Año:
2015
Tipo del documento:
Article