Iridium‐Catalyzed, Silyl‐Directed, peri‐Borylation of C−H Bonds in Fused Polycyclic Arenes and Heteroarenes

Abstract

peri-Disubstituted naphthalenes exhibit interesting physical properties and unique chemical reactivity, due to the parallel arrangement of the bonds to the two peri-disposed substituents. Regioselective installation of a functional group at the position peri to 1-substituted naphthalenes is challenging due to the steric interaction between the existing substituent and the position at which the second one would be installed. We report an iridium-catalyzed borylation of the C-H bond peri to a silyl group in naphthalenes and analogous polyaromatic hydrocarbons. The reaction occurs under mild conditions with wide functional group tolerance. The silyl group and the boryl group in the resulting products are precursors to a range of functional groups bound to the naphthalene ring through C-C, C-O, C-N, C-Br and C-Cl bonds.

Iridium‐Catalysed C−H Borylation of Heteroarenes: Balancing Steric and Electronic Regiocontrol

“…In a similar fashion to 2‐arylpyridines, hemilabile ligands facilitate selective remote borylation of 1‐aryl isoquinolines (Scheme 28 c), [132] whilst hydrosilyl relay direction enables peri borylation of suitable 1‐substituted isoquinolines (Scheme 28 d). [73] Curiously, similar chemistry using 2‐chloro‐4‐hydrosilylquinoline 265 was not viable (Scheme 28 e) and this result highlights the degree of substrate specificity that exist in these more complex systems that have multiple influences on reaction outcomes.…”

“…In this process,t he substrate contains an additional reactive functional group which can ligate the metal centre,displacing one of the boron ligands.A ss uch, binding of the directing group with the metal centre does not necessarily require additional vacant coordination sites. [72][73][74][75][76] One such example involves the borylation of hydrosilyl arene 46,w hich undergoes selective ortho C À Ha ctivation following substrate binding to the Ir centre via addition of the Si À Hb ond (Scheme 6b). Outersphere directed borylation is ac omplementary process in which asubstrate interaction with aligand of the catalytically active species leads to regioselective CÀHa ctivation (Figure 3c).…”

C–H Functionalization Strategies in the Naphthalene Series: Site Selections and Functional Diversity

“…Hartwig reported an efficient silyl-directed borylation in the presence of [Ir(cod)OMe] 2 and phenanthroline-based ligands. 63 An interesting aspect of this strategy relies on the possible transformation of both boryl and silyl groups into valuable functional groups including aryl, halide, azide or hydroxy, expanding the functional diversity on naphthalene platforms. Similarly, thioethers were shown to efficiently direct C8-H arylation reactions using Rh/Ag as the catalytic combination and boronic acids.…”

Iridium‐katalysierte C‐H‐Borylierung von Heteroarenen: Eine Balance zwischen sterischer and elektronischer Regiokontrolle

“…In diesem Fall hat das Substrat eine zusätzliche funktionelle Gruppe, die am Zentralatom koordiniert und dabei einen Borliganden ersetzt. Dabei benötigt die bindende dirigierende Gruppe nicht zwangsläufig eine zusätzliche unbesetzte Koordinationsstelle [72–76] . Ein Beispiel dafür ist die Borylierung von Hydrosilylaren 46 , das selektiv in ortho ‐Stellung aktiviert wird, nachdem das Substrat durch Addition der Si‐H‐Bindung an das Iridiumzentralatom gebunden hat (Schema 6 b).…”

“…In einer ähnlichen Weise wie bei 2‐Arylpyridinen fördern hemilabile Liganden die selektive Borylierung von 2‐Arylisochinolinen (Schema 28 c), [132] während eine Relay‐dirigierte Aktivierung mithilfe einer Hydrosilylgruppe zur peri ‐Borylierung von geeigneten 1‐substituierten Isochinolinen führt (Schema 28 d). [73] Interessanterweise war eine ähnliche Reaktion mit dem 2‐Chlor‐4‐hydrosilylchinolin 265 nicht erfolgreich (Schema 28 e); dieses Resultat zeigt den Grad an Substratspezifität auf, der in diesen komplexeren Systemen mit vielen Einflüssen auf das Reaktionsergebnis vorliegt.…”