Biaryl Construction via Ni-Catalyzed C−O Activation of Phenolic Carboxylates

Abstract

Biaryl scaffolds were constructed via Ni-catalyzed aryl C-O activation by avoiding cleavage of the more reactive acyl C-O bond of aryl carboxylates. Now aryl esters, in general, can be successfully employed in cross-coupling reactions for the first time. The substrate scope and synthetic utility of the chemistry were demonstrated by the syntheses of more than 40 biaryls and by constructing complex organic molecules. Water was observed to play an important role in facilitating this transformation.

State‐of‐the‐Art in Metal‐Catalyzed Cross‐Coupling Reactions of Organoboron Compounds with Organic Electrophiles

“…[58]. Moreover, these carboxylates are much more environmentally friendly, generating acetate salts as the only by-product in the Suzuki-Miyaura cross-coupling reaction [59,60]. Despite these advantages, the main hurdle in cross-coupling reactions of O-acylated phenols is the selective activation of the C-OAc bond over the carbonyl C-O bond (Eq.…”

“…As shown in Scheme 2.16, the bond dissociation energy of the C-OAc bond is 106 kcal mol −1 , which is considerably higher than the bond dissociation energy of the carbonyl C-O bond (80 kcal mol −1 ). This energy difference makes the selective activation of the desired C-OAc bond a difficult task [59]. In spite of this significant obstacle, by employing NiCl 2 (PCy 3 ) 2 as the catalyst, the groups of Garg [58] and Shi [59] independently developed catalytic systems that are capable of effecting cross-coupling of O-acylated phenols with arylboronic acid derivatives (Eqs.…”

“…This energy difference makes the selective activation of the desired C-OAc bond a difficult task [59]. In spite of this significant obstacle, by employing NiCl 2 (PCy 3 ) 2 as the catalyst, the groups of Garg [58] and Shi [59] independently developed catalytic systems that are capable of effecting cross-coupling of O-acylated phenols with arylboronic acid derivatives (Eqs. (10) and (11), Scheme 2.16).…”

C(Aryl)‐O‐Aktivierung von Arylcarboxylaten in nickelkatalysierten Biarylsynthesen

“…[11] Bei der Reaktion niedervalenter Metallkomplexe bilden sich daher bevorzugt die Acylkomplexe. Dieser Reaktionsmodus wird bei einigen katalytischen Umsetzungen genutzt, z.…”

“…[15] Der Gruppe um Shi gelang eine solche Kreuzkupplung unter C(Aryl)-O-Aktivierung für Arylester verschiedener Carbonsäuren, wobei die besten Ergebnisse bei der Kupplung mit Arylboroxinen erneut mit Arylpivalaten erzielt wurden. [11] Beide [16] und schließlich der reduktiven Eliminierung des Produktes.…”