PdCl₂ and N‐Hydroxyphthalimide Co‐catalyzed CH Hydroxylation by Dioxygen Activation

Abstract

Sanfte „Verbrennung“: Die Titelreaktion gelingt durch eine Kombination aus übergangsmetallkatalysierter C‐H‐Aktivierung und einem NHPI‐initiierten Radikalprozess. Die neutralen Bedingungen und das ideale Oxidationsmittel, molekularer Sauerstoff, machen diese Hydroxylierung zu einem umweltschonenden und praktischen Prozess. NHPI=N‐Hydroxyphthalimid.

Synthesis of Phenolic Compounds via Palladium Catalyzed C−H Functionalization of Arenes

“…Jiao et al described an aerobic direct CÀHh ydroxylation of 2-arylpyridines using toluene as solvent, palladium chloride (PdCl 2 )a sc atalyst and N-hydroxyphthalimide (NHPI)a sc o-catalyst ( Figure 39). [28] The reactionp roceeded well with as eries of substituted 2-phenylpyridines containinge lectron-withdrawing and electron releasing functional groups.…”

Direct C(sp2)−H Hydroxylation of Arenes with Palladium(II)/Oxygen Using Sulfoximines as a Recyclable Directing Group

“…Although the production of substituted phenols by using the Pd II /O 2 catalytic system has been reported, the existing methods require harsh reactionc onditions, [5] additional oxidants and bases, [6] or pyridine-based directing groups along with ac o-catalyst. [7] Recently,o ur group introduced an ovel methodf or the CÀHh ydroxylation of 2-arylpyridines with O 2 by simultaneous cooperation of aldehyde autoxidationw ith palladium catalysis. [8] However, the use of the pyridine moiety, which is not easily removable or modifiable, as ad irecting group limited application of this method.…”

“…Finally,a n 18 O-labeling experiment provedt hat the oxygen atom of the hydroxy group indeed originated from molecular oxygen [Eq. (7)],asahydroxylated product with 89 % 18 Oincorporation was obtained.…”

Oxygen‐Promoted CH Bond Activation at Palladium

“…The functionalization of CH bonds with such oxygenase catalysts is particularly desirable. While there are a few examples of oxygenase‐type CH functionalization reactions using O 2 ,6–10 the majority of the palladium catalysts for CH functionalization employ oxidants other than molecular oxygen 11…”