Iridium‐Catalyzed Intramolecular C–H Silylation of Siloxane‐Tethered Arene and Hydrosilane: Facile and Catalytic Synthesis of Cyclic Siloxanes

Abstract

Catalytic C–H silylation is an increasingly important topic in the field of organosilicon chemistry and homogenous catalysis as well as organic synthesis, but such syntheses and transformations are usually challenging and often incompatible with some functional groups. In this manuscript, a new type of silanol‐directed intramolecular dehydrogenative silylation under iridium catalysis has been developed. The described silylative cyclization has good functional group compatibility, providing a general and efficient route to unsymmetrical cyclic siloxanes with multiple potentially modifiable silicon atoms in high site‐selectivities. The resulting organosilicon compounds exhibit diverse synthetic applications owing to their unique structures.magnified image

Palladium-Catalyzed Catellani-Type Bis-silylation and Bis-germanylation of Aryl Iodides and Norbornenes

“…Our group recently disclosed a Pd-catalyzed Catellani-type silylation reaction using oxanorbornadiene as an ortho -C–H activator and ethylene surrogate for the assembling of ( Z )-β-substituted vinylsilanes . As research continues, we report herein a palladium-catalyzed Catellani-type bis-silylation reaction of aryl iodides and NBEs, affording disilanes bearing one C­(sp 2 )–Si bond and one secondary C­(sp 3 )–Si bond stereoselectively (Scheme c). − …”

Construction of Si‐Stereogenic Silanes through C−H Activation Approach

“…Inspired by Rh‐ or Ir‐catalyzed Si−H/C−H dehydrogenative coupling silylation reactions to construct carbon‐stereogenic diarylmethanols developed by Hartwig and Shi, [27] Zhao and coworkers recently reported iridium‐catalyzed asymmetric desymmetrization of diarylsilanols with the same strategy (Scheme 17). [28] Notably, the Ir‐catalyzed nonchiral variant of this reaction for synthesis of cyclic siloxanes has been previously reported by the Xu group [29] . With chiral ligand L15 , the silicon‐stereogenic tetrasubstituted cyclic siloxanes were accessible with excellent enantioselectivities (up to 95 % ee).…”

“…[28] Notably, the Ir-catalyzed nonchiral variant of this reaction for synthesis of cyclic siloxanes has been previously reported by the Xu group. [29] With chiral ligand L15, the silicon-stereogenic tetrasubstituted cyclic siloxanes were accessible with excellent enantioselectivities (up to 95 % ee). Interestingly, an optically pure diol bearing a Si-stereogenic silanol structure could be synthesized upon Tamao-Fleming oxidation and recrystallization, which can be used as a precursor for the preparation of a class of chiral phosphoramidites.…”

Recent Progress in Transition Metal‐Catalyzed Hydrosilane‐Mediated C−H Silylation

“…Inspired by previous works, Cui and Xu group successfully realized iridium‐catalyzed intramolecular C(sp 2 )−H silylation of siloxane‐tethered arene and hydrosilanes to provide a variety of five‐membered and six‐membered unsymmetrical cyclic siloxanes likely via six‐membered and seven‐membered iridium metalacyclic states (Scheme 10(d)) [15] . The strategy exhibited good functional group compatibility, high efficiency and regioselectivity, allowing for further transformations to enrich the diversity of organosilicon compounds.…”