Frontispiece: Enantioselective Intermolecular C−H Silylation of Heteroarenes for the Synthesis of Acyclic Si‐Stereogenic Silanes

Abstract

Asymmetric Catalysis An enantioselective intermolecular C−H silylation of heteroarenes for the synthesis of acyclic Si‐stereogenic silanes is reported by Chuan He et al. in their Communication (e202117820).

Copper-Catalyzed Desymmetrization of Prochiral Silanediols to Silicon-Stereogenic Silanols

“…In recent years, enantioselective construction of silicon-stereogenic silanes has received increasing attention in organic synthesis given that these non-natural chiral silanes can serve as versatile chiral auxiliaries, reagents, building blocks, and catalysts or ligands. − Among the many elegant approaches, rhodium-catalyzed desymmetrization of prochiral dihydrosilanes or tetraorganosilanes have been the focus of the most attention and have delivered a number of new transformations giving rise to various silicon-stereogenic silanes. − In most cases, the discrimination of a Si–H or a Si–C bond is generally enabled by the chiral-Rh­(I)-catalyst-mediated desymmetric oxidative addition, which subsequently delivers the crucial chiral Rh–Si intermediate to proceed further stereospecific transformation, thereby furnishing the desired silicon-stereogenic silane products (Scheme b, top). ,− In view of the current state of the art for the Rh-catalyzed desymmetrization of prochiral dihydrosilanes or tetraorganosilanes, as well as the challenge for the access of silicon-stereogenic silanols, we questioned whether we could develop a new catalytic approach toward enantioenriched silanols via the desymmetrization of prochiral silanediols (Scheme a, right). Practically, unlike their carbon analogues, silanediols are easy to access with reasonable stability.…”

Rhodium-Catalyzed Asymmetric C–H Functionalization Reactions

“…134 Then, a possible mechanism was proposed. The reaction proceeds with the coordination of thiophene to the Rh−H catalyst (171) 135 The presence of NBE-OMe (5-(methoxymethyl)bicyclo-[2.2.1]hept-2-ene), as a bulky hydrogen acceptor, could accelerate the dehydrogenative C−H silylation process.…”

“…Reductive elimination of 172 occurs to generate the intermediate 173 , and subsequent C–H activation and reductive elimination produces the desired acyclic chiral monohydrosilane 170 and regenerates the Rh–H catalyst. Recently, the He group also accomplished an intermolecular asymmetric C–H silylation of heteroarenes, delivering various acyclic silicon-stereogenic heteroaryl monohydrosilanes 176 from simple dihydrosilanes 175 (Scheme c) . The presence of NBE-OMe (5-(methoxymethyl)­bicyclo-[2.2.1]­hept-2-ene), as a bulky hydrogen acceptor, could accelerate the dehydrogenative C–H silylation process.…”