An atom-economic intermolecular radical addition reaction of acyloxy nitroso compounds to electron-deficient alkenes mediated by visible light is reported. The starting nitroso derivatives are readily prepared by oxidation of the corresponding oximes prepared from ketones and the overall transformation represents an oxidative coupling of a ketone with a Michael acceptor. The cascade proceeds smoothly under mild conditions, providing a series of valuable functionalized oximes in moderate to good yields. Mechanistic studies suggest that these cascades proceed via addition/coupling processes that are controlled by the persistent radical effect (PRE) with NO acting as the persistent species.
A metal-free
radical 1,2-difunctionalization of activated alkenes
with various silanes and tert-butyl nitrite is reported.
The radical cascade occurs by light-promoted homolytic O–NO
bond cleavage of tert-butyl nitrite and subsequent
hydrogen atom abstraction by the alkoxyl radical from the silane.
Silyl radical addition to the alkene and highly selective cross-coupling
of the NO radical with the Si-adduct C-radical provide the silyl-oximation
product in moderate to good yields. The reaction features good functional
group tolerance and is easily scaled up.
An atom-economic thermal α,β-difunctionalization of various styrenes with readily prepared azodioxy compounds is reported. Mechanistic studies reveal that the starting azodioxy compounds can thermally be cleaved to the corresponding C-nitroso...
Eine durch sichtbares Licht vermittelte, atomçkonomische, intermolekulare Radikal-Additionsreaktion von Acyloxy-Nitroso-Verbindungen an elektronenarme Alkene wird beschrieben. Die Nitroso-Ausgangsderivate lassen sich leicht durch Oxidation der entsprechenden Keton-abgeleiteten Oxime herstellen, und die gesamte Sequenz stellt eine oxidative Kupplung eines Ketons mit einem Michael-Akzeptor dar. Die Kaskade läuft unter milden Bedingungen ab und liefert eine Reihe von wertvoll funktionalisierten Oximen in moderaten bis guten Ausbeuten. Mechanistische Studien deuten darauf hin, dass diese Kaskaden über Additions-/Kupplungsprozesse ablaufen, die durch den "Persistent Radical Effect" (PRE) kontrolliert werden, wobei das NO-Radikal als persistente Spezies agiert.
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