NBE-Controlled Palladium-Catalyzed Interannular Selective C–H Silylation: Access to Divergent Silicon-Containing 1,1′-Biaryl-2-Acetamides

Abstract

A novel palladium-catalyzed interannular selective C–H silylation of 1,1′-biaryl-2-acetamides is described. The combination of palladium catalyst with copper oxidant enables meta- or ortho-selective C–H silylation by employing hexamethyldisilane as a trimethylsilyl source, which relies on the control of NBE derivatives as a switch, thus providing straightforward access to divergent silicon-containing 1,1′-biaryl-2-acetamides.

Palladium-Catalyzed ortho-C(sp2)–H Silylation of Aromatic Ketones Using an Aminooxyamide Auxiliary

“…Using the same AQ auxiliary, Zhang developed a palladium-catalyzed vinylic C­(sp 2 )–H silylation reaction of acrylamides to make Z -vinylsilanes . In 2019, Yang reported a palladium-catalyzed interannular ortho -selective C­(sp 2 )–H silylation of 1,1′-biaryl-2-acetamides with copper oxidant . In 2020, Shi developed a Pd-catalyzed ortho -C–H silylation of biaryl aldehydes enabled by a transient auxiliary .…”

“…8 In 2019, Yang reported a palladiumcatalyzed interannular ortho-selective C(sp 2 )−H silylation of 1,1′-biaryl-2-acetamides with copper oxidant. 9 In 2020, Shi developed a Pd-catalyzed ortho-C−H silylation of biaryl aldehydes enabled by a transient auxiliary. 10 Moreover, remote meta-and para-selective C(sp 2 )−H silylation using palladium catalysis and directing group strategy were also reported.…”

Copper-Catalyzed Direct sp2 C–H Silylation of Arylamides Using Disilanes

“…Control experiments proved the crucial role of copper catalyst and silver oxidant (entries 17–18) for the silylation, as the desired products were not formed when these were excluded. The present methodology required an excess amount of disilanes as a reaction partner, as was evident from known literature reports, which also needed superstoichiometric amounts of disilanes for effective silylation of unactivated C–H bonds. This might be due to the lesser reactivity of a strong Si–Si bond since both (PhMe 2 Si) 2 and (Ph 2 MeSi) 2 remained unreacted when they were used for the substrate scope.…”

“…On the basis of the preceding experimental results and previous literature reports, − a reaction pathway is proposed as in Scheme . In accordance with the known coordination properties of Cu­(II), benzamide 1a first generates the intermediate A in the presence of CuX 2 (X = acetate/carbonate) with the aid of complexation by an N , N -bidentate 8-aminoquinoline directing group.…”

“…In consequence, significant efforts have been made in recent years for the strategic installation of silyl groups into organic frameworks. Among these, the synthesis of organosilanes through transition-metal-catalyzed direct C–H bond functionalizations, as compared to traditional approaches of silylation reactions and transition-metal-free techniques, has emerged as the most sought-after protocol from the viewpoints of atom economy and high efficiency. − The high abundance, low cost, and environmentally benign nature of silicon have in addition allowed the development of catalytic silylation methods via C–H bond activation. In the past decades, several advances have been made in this field for the silylation of C­(sp 2 )–H as well as C­(sp 3 )–H variants using Ru, Rh, Ir, Sc, and Pt as transition metal catalysts (Scheme a).…”