Cyclopalladated 2-t-butyl-4,4-dimethyl-2-oxazoline: its preparation, and use in the functionalisation of a non-activated carbon-hydrogen bond

Complementary Strategies for Directed C(sp3)−H Functionalization: A Comparison of Transition‐Metal‐Catalyzed Activation, Hydrogen Atom Transfer, and Carbene/Nitrene Transfer

“…[11] It is believed that after the coordination of the oxime nitrogen atom to the palladium(II) catalyst, ac oncerted metalation/deprotonation event between the substrate and the Pd II catalyst leads to the formation of alkylPd II intermediate B1.Oxidation of Pd II to Pd IV by PhI(OAc) 2 drives reductive elimination to furnish the CÀOb ond. In addition, Sanford and co-workers found that pyridine can also be applied as ad irecting group for the acetoxylation of primary C À Hb onds,a si llustrated by the conversion of pyridine 12 into 13.Y ua nd co-workers [12] reported the palladium(II)-catalyzed iodination of unactivated primary C(sp 3 )ÀHbonds of oxazolines,substrates that had previously been shown to undergo cyclopalladation with astoichiometric amount of palladium [13] (Scheme 4). Iodine is included as an additional oxidant, accounting for the observed iodination of oxazoline 14 to 15,i nstead of acetoxylation.…”

Cyclopalladation of 2-tert-butyl-4,4-dimethyl-2-oxazoline in solution and on silica gel

“…Cyclopalladation of oxazoline 1 by Pd(OAc) 2 in AcOH was previously reported by Balavoine and Clinet [11]. According to their study, two cyclometallated complexes, 2 and 3, were formed in 62 and 16% yield, respectively, after refluxing the reagents in AcOH for 2 h. The major compound 2 had a dimeric structure, while the minor product 3 was a trinuclear derivative.…”

“…Compound 3 was also converted to complex 4 in 96% yield by treatment with LiCl in MeOH (Scheme 2) [11]. The authors [11] provided no proof of the proposed structure and no spectral data for complex 4.…”

“…According to their study, two cyclometallated complexes, 2 and 3, were formed in 62 and 16% yield, respectively, after refluxing the reagents in AcOH for 2 h. The major compound 2 had a dimeric structure, while the minor product 3 was a trinuclear derivative. Reaction of complex 2 with LiCl in Ac 2 O afforded the μ-Cl analog 4 in 92% yield [11]. Compound 3 was also converted to complex 4 in 96% yield by treatment with LiCl in MeOH (Scheme 2) [11].…”

Komplementäre Strategien für die dirigierte C(sp3)‐H‐Funktionalisierung: ein Vergleich von übergangsmetallkatalysierter Aktivierung, Wasserstoffatomtransfer und Carben‐ oder Nitrentransfer

“…Yu [12] berichtete über die Palladium(II)-katalysierte Iodierung nichtaktivierter primä-rer C(sp 3 )-H-Bindungen von Oxazolinen, fürd ie zuvor nachgewiesen wurde,d ass sie als Substrate eine Cyclopalladierung mit einer stçchiometrischen Menge an Palladium erfahren (Schema 3). [13] Iod wird als zusätzliches Oxidationsmittel einbezogen und bewirkt anstelle einer Acetoxylierung die Iodierung des Oxazolins 14 zu 15.D augulis entdeckte,d ass Picolinamide als zweizähnige Liganden bei der palladiumkatalysierten C-H-Aktivierung dienen kçnnen. [14] Im spezifischen Fall wurden nichtaktivierte C(sp 3 )-H-Bin- [16] oder Aniline [17] abgefangen werden kçnnen, was zur Arylierung bzw.A minierung der Methyl-C-H-Bindungen [20] Baudoin erweiterte erfolgreich den Anwendungsbereich dieser Reaktionen, indem er Vinylhalogenide als spurlose dirigierende Gruppe einsetzte.S ok ann die Methyl-C-HBindung des Vinylbromids 35 fürd ie Synthese des bicyclischen Pyrrolidins 36 aktiviert werden (Schema 7).…”