Rhodium-HMPT-catalyzed direct ortho arylation of phenols with aryl bromides

Pd(II)-Catalyzed ortho- or meta-C–H Olefination of Phenol Derivatives

“…10 Despite a number of elegant directing groups previously developed for the ortho -C–H functionalizations of phenols, 5–9 the distance between the C–H bonds and the functional groups in α-phenoxyacetic acids presents a challenge. Although we have developed various ortho -C–H funcationalizations of phenylacetic acids via a relatively distal directing group, the ortho - C–H bonds and the chelating atom of the carboxyl group in α-phenoxyacetic acids are further apart (six bonds away) as shown in ciprofibrate (Figure 3).…”

“…4 Bedford and others succeeded in using catalytic amount of phosphites as directing groups to promote Rh(I)-catalyzed ortho -arylation of phenols (Fig 1). 5 Hartwig reported Ir(I)-catalyzed borylation of hydrosilyl ethers of phenols. 6 Recent emergence of C–H activation reactions with Pd(II), 7 Rh(III), 8 Ru(II) 9 catalysts using weakly coordinating carbonyls have led to a range of ortho -C–H functionalization reactions of phenol derivatives (Fig 1).…”

Transition‐Metal‐Catalyzed Direct Arylation of (Hetero)Arenes by CH Bond Cleavage

“…[202,203] As a result, the specific phosphinite co-catalyst needs to be prepared for each individual substrate prior to catalysis to avoid formation of undesired and difficult to separate by-products. This limitation was independently addressed by Oi, Inoue et al [204] as well as by Bedford and Limmert, [205] with the use of inexpensive P(NMe 2 ) 3 as the cocatalyst. Thus, a system comprising [{RhCl(cod)} 2 ] and P-(NMe 2 ) 3 proved complementary to the previously reported phosphinite-based catalyst, in that efficient functionalizations of ortho-unsubstituted phenols proved viable (Scheme 112).…”

Übergangsmetallkatalysierte direkte Arylierungen von (Hetero)Arenen durch C‐H‐Bindungsbruch

“…[202,203] Im Ergebnis muss der jeweilige Phosphinit-Cokatalysator für jedes spezielle Substrat eigens hergestellt werden, um die Bildung unerwünschter und schwierig abzutrennender Nebenprodukte zu vermeiden. Oi, Inoue et al [204] sowie Bedford et al [205] fanden unabhängig voneinander, dass diese Einschränkung durch die Verwendung von preiswertem P(NMe 2 ) 3 als Cokatalysator überwunden werden kann. Ein solches Katalysatorsystem aus [RhCl(cod)] 2 und P(NMe 2 ) 3 ergänzt somit den bereits beschriebenen Phosphinit-Katalysator, indem es die Funktionalisierung von in ortho-Position unsubstituierten Phenolen ermöglicht (Schema 112).…”