Versatile Tetrasilane for Time-Controlled Palladium-Catalyzed Divergent Synthesis of Silacycles via C–H Activation

Abstract

Transition-metal-catalyzed intermolecular annulation of silicon reagents with organic molecules is still underdeveloped due to the scarcity of silicon reagent types and their diverse reactivity. Herein, a readily accessible silicon reagent (octamethyl-1,4-dioxacyclohexasilane) has been developed for divergent synthesis of silacycles via time-controlled palladiumcatalyzed cascade C−H silacyclization. This protocol enables the rapid and selective transformation of acrylamides into spirosilacycles with different ring sizes, including benzodioxatetrasilecines, benzooxadisilepines, and benzosiloles, in moderate to good yields through a time switch. Notably, the tetrasilane reagent can also be utilized for C−H silacyclization of 2-halo-Nmethacryloylbenzamides and 2-iodobiphenyls, leading to diverse fused silacycles. Furthermore, several synthetic transformations of products are achieved. A series of mechanistic studies demonstrate the transformation relationships and possible pathways among ten-, seven-, and five-membered silacycles.

Norbornene Derivatives-Controlled Palladium-Catalyzed Divergent Synthesis of Dibenzo[a,c]cycloheptenones and Fluorenones from Aryl Iodides and α-Oxocarboxylic Acids

“…Despite great progress, the application of α-oxocarboxylic acids in the Catellani reaction has not been reported yet. Inspired by these reports and our ongoing interest in decarboxylative cyclizations and the transformations of palladacycles, , we envisioned that aryl iodides undergo an oxidative addition, followed by NBE derivatives insertion, then C–H bond activation to generate palladacycle B , which can be intercepted by α-oxocarboxylic acids to achieve divergent syntheses of dibenzo­[ a , c ]­cyclohepteneones and fluorenones by tuning the chemoselectivity with NBE derivatives (Scheme c). Herein, we detail our results.…”

Pd(0)-Catalyzed Intermolecular Methylene C(sp3)–H Silylation by Using N-Heterocyclic Carbene Ligands

“…Next, C reacts with hexamethyl disilane via oxidative addition to give Pd­(IV) species E . E undergoes dual reductive elimination to yield the final product 3a and regenerate Pd(0) …”