Carboxylic Acids as Traceless Directing Groups for Formal meta‐Selective Direct Arylation

Abstract

Without a trace: The first meta‐selective direct CH arylation that uses iodoarenes as coupling partners is reported (see scheme, EWG=electron‐withdrawing group). This process utilizes carboxylic acid units as temporary directing groups that are cleaved during the reaction, leaving no trace in the resulting biaryl products.

The use of carboxylic acids as traceless directing groups for regioselective C–H bond functionalisation

“…This was further demonstrated in 2011 in a paper by Larrosa and co-workers. 41 The authors applied the traceless directing group strategy to ortho-substituted benzoic acids to achieve meta-substituted biaryl scaffolds using aryl iodides as the coupling partners and Pd(OAc) 2 as the catalyst (Scheme 20). This protocol exploited the preference of palladium to decarboxylate electron rich bis-ortho-substituted benzoic acids (Scheme 6) to tackle the selective protodecarboxylation of the arylated benzoic acid product over the benzoic acid starting material.…”

Palladium-catalyzed non-directed C–H bond arylation of difluorobenzenes and dichlorobenzenes bearing benzoxazole or benzothiazole

“…24,25 In order to address the lower reactivity of less-electron deficient fluorobenzenes, 14,26,27 directing group (e.g., carboxylic acid) strategy have been employed. 28,29 On other hand, benzoxazole unit has been employed as directing group for the regioselective C2 arylation of phenyl using a palladium catalyst in the presence of silver carbonate in trifluoroacetic acid ( Figure 2b). 30,31 A similar procedure was reported by Ding, Peng and coworkers for the direct C2 arylation of 2-arylbenzothiazole ( Figure 2c).…”

Rhodium‐katalysierte Anellierung von Benzoesäuren mit α,β‐ungesättigten Ketonen durch C‐H‐, CO‐OH‐ und C‐C‐ Bindungsspaltung

“…[1] Anfangs wurden diese Reaktionen jedoch oftmals durch komplexe dirigierende Gruppen limitiert, [2] deren Einführung und spätere Entfernung die Atomçkonomie beeinträchtigen. [6] Aufbauend auf Pionierarbeiten von Miura, [7] wurde eine Vielzahl carboxylatdirigierter sp 2 C-H-ortho-Funktionalisierungen von Yu, [8] Li, [9] Daugulis, [10] Larrosa, [11] Ackermann, [12] Su, [13] Baidya, [14] unserer Gruppe [15] und anderen [16] entwickelt. [5] Entscheidende Vorteile von Carbonsäuren als dirigierende Gruppe sind eine breite Verfügbarkeit und die Mçglichkeit der Protodecarboxylierung oder weiterer ipso-Funktionalisierungen in Form von regiospezifischen C-C-oder C-Heteroatom-Bindungsknüpfungend urch decarboxylierende Kupplungen.…”