Palladium-Catalyzed Aromatic C–H Bond Nitration Using Removable Directing Groups: Regiospecific Synthesis of Substituted o-Nitrophenols from Related Phenols

Abstract

A general and regiospecific transformation of substituted phenols into the related o-nitrophenols has been achieved via a three-step process involving the palladium-catalyzed chelation-assisted ortho-C-H bond nitration as the key step. In the process, 2-pyridinyloxy groups act as removable directing groups for the palladium-catalyzed ortho-nitration of substituted 2-phenoxypridines, and they can be readily removed in the subsequent conversion of the resulting 2-(2-nitrophenoxy)pyridines into 2-nitrophenols.

Copper–cobalt synergy in Cu1−xCoxFe2O4spinel ferrite as a highly efficient and regioselective nanocatalyst for the synthesis of 2,4-dinitrotoluene

“…an important and necessary precursor to polyurethane resins employed for rigid and exible foams, coatings, elastomers, and bers. Aer the original work by Othmer and co-workers 24 in 1944, further progress for nitration of aromatic compounds was achieved by Adamiak and co-worker, 25 Gao et al, 26 Liu et al, 27 and Green et al 28 in the recent years. 11 However, separation of 2,4-DNT from 2,6-DNT is a difficult and expensive work.…”

Transition Metal‐Catalyzed Directing‐Group‐Assisted C−H Activation of Phenols

“…The Pd‐catalyzed ortho ‐C−H nitration of phenols with AgNO 2 and tert ‐butyl nitrite (TBN) were also reported by Liu's group and Jiao's group, respectively (Scheme ). The NO 2 radical 22 was generated in both methods.…”

Redoxaktive NOx‐Liganden in palladiumvermittelten Prozessen

“…[64] Darüber hinaus zeigten Cµmpora et al,d ass Pd-NO-Addukte charakterisiert werden kçnnen. [21] Aufbauend auf den Arbeiten der Gruppen von Tisue [17] und Norman [18,19] (siehe Abschnitt 1) ist die katalytische aromatische Nitrierung sowohl mit abspaltbaren [65] als auch nicht abspaltbaren [66] dirigierenden Gruppen am Pd in Gegenwart von MNO 2 -Salzen durchführbar,w as auch Erkenntnissen über klassische Kreuzkupplungsprozesse entspricht, [67] in denen ein spezieller Phosphanligand zur Auslçsung einer reduktiven Nitriteliminierung am Pd II erforderlich ist. Die neueren Arbeiten der Gruppen von Ranu [68] und Jiao [69] sind besonders erwähnenswert, da in diesen eine katalytische aromatische Nitrierung unter Verwendung von tert-Butylnitrit (TBN) mit molekularem O 2 gelang.…”