Rhodium‐Catalyzed Enantioselective Intramolecular CH Silylation for the Syntheses of Planar‐Chiral Metallocene Siloles

Abstract

Reported herein is the rhodium-catalyzed enantioselective C-H bond silylation of the cyclopentadiene rings in Fe and Ru metallocenes. Thus, in the presence of (S)-TMS-Segphos, the reactions took place under very mild conditions to afford metallocene-fused siloles in good to excellent yields and with ee values of up to 97%. During this study it was observed that the steric hindrance of chiral ligands had a profound influence on the reactivity and enantioselectivity of the reaction, and might hold the key to accomplishing conventionally challenging asymmetric C-H silylations.

Ir-Catalyzed Enantioselective, Intramolecular Silylation of Methyl C–H Bonds

“…In 2015, Shibata, He, and Takai independently reported enantioselective silylations of aromatic C–H bonds that form chiral ferrocenes (Scheme 1a, middle) catalyzed by Rh complexes of chiral bisphosphine or diene ligands. 11 He et al reported Rh-catalyzed tandem desymmetrizations of silacyclobutanes and silylations of C–H bonds to construct chiral tetraorganosilanes. 12 Our group reported Rh-catalyzed enantioselective silylations of aromatic C–H bonds in diarylmethanols (Scheme 1a, right) 13 and silylations of cyclopropyl C–H bonds (Scheme 1b, left).…”

Synthesis of Substituted Naphtho‐Ferrocenes via a Gold(I)‐Catalyzed Intramolecular 6‐endo‐Dig Cyclization

“…Herein, we reported an efficient gold-catalyzed [5,8] intramolecular 6-endo-dig cyclization of 1-ferrocenyl-2-(1-alkynyl)benzenes which were easily prepared via palladium-catalyzed Negishi coupling [9] and Sonogashira coupling [10,11] reaction (Scheme 2), to give structurally diverse naphtho-ferrocenes derivatives under very mild reaction conditions (Scheme 1c). …”

A Chiral Nitrogen Ligand for Enantioselective, Iridium‐Catalyzed Silylation of Aromatic C−H Bonds

“…[8] In 2015, Shibata, He, and Takai independently reported enantioselective silylations of C-H bonds in ferrocenes catalyzed by rhodium complexes containing diene or diphosphine ligands (Scheme 1a, middle). [8b, 9] Recently, one of our groups reported enantioselective silylations of aryl C-H bonds with ee values of 72 to 99% catalyzed by rhodium complexes ligated by chiral diphosphines (Scheme 1a, right). [10] …”