Pd(II)-Catalyzed Phosphorylation of Aryl C–H Bonds

Abstract

A Pd(II)-catalyzed C-H phosphorylation reaction has been developed using heterocycle-directed ortho-palladation. Both H-phosphonates and diaryl phosphine oxides are suitable coupling partners for this reaction.

Substrate‐Directed C‐H Functionalization of 2‐Aryl Pyridines by Transition Metal Complexes

“…[92] t-AmylOH proved to be the best solvent for this reaction. A variety of 2-aryl pyridine substrates were phosphorylated to give the N À P bisdentate compounds which are potentially useful in medicinal chemistry and catalysis.…”

“…In 2011, Ellman et al developed a Co(III)-catalyzed amidation of 2-aryl pyridines (3) with alkyl/aryl isocyanates (92) to produce the corresponding amide derivatives (93) (Scheme 46). [62] In 2012, Cheng et al also reported a Ru(II)-catalyzed amidation reaction of 2-aryl pyridines (3) with isocyanates (94) via C À H bond activation to obtain the amides (95) in excellent yields (Scheme 47).…”

Recent Advances in H-Phosphonate Chemistry. Part 2. Synthesis of C-Phosphonate Derivatives

“…A pyridine-directed, palladium-catalyzed phosphonylation of C(sp 2 )-H bonds was reported by Murakami et al [125] and Yu et al [126]. A perennial problem in this type of reaction is a strong, competing coordination of phosphorus nucleophiles which may hamper the process of activation of less coordinative C-H bonds.…”

“…In addition, NMMI was found to be an indispensable reaction component which enabled reductive elimination of the products from the corresponding aryl(phosphonate)Pd(II) complexes. Also, Yu et al [126] developed a catalytic system for C-H phosphonylation of 2-aminoaryl scaffolds, similar to the system shown in Scheme 18. In this instance, the Pd(II)-catalyst deactivation was attenuated by a slow addition of H-phosphonate diesters (ethyl, isopropyl), and p-benzoquinone was used to facilitate the reductive elimination step.…”

Pyridine‐Directed Palladium‐Catalyzed Phosphonation of C(sp2)H Bonds

“…Very recently, Yu and co-workers reported a pyridine-directed CÀH phosphonation reaction catalyzed by palladium, in which H-phosphonates were directly used. [5] Expeditious deactivation of the catalyst was avoided by adding H-phosphonate slowly with a syringe pump. Herein, we describe our independent study of the analogous phosphonation reaction of 2-arylpyridines; an ahydroxyalkylphosphonate generates H-phosphonate upon treatment with a base, [6] which serves as the masked phosphonating reagent [7] to save the catalyst from deactivation.…”