Streamlined Construction of Silicon-Stereogenic Silanes by Tandem Enantioselective C–H Silylation/Alkene Hydrosilylation

Abstract

A rhodium-catalyzed tandem enantioselective C–H silylation/alkene hydrosilylation of dihydrosilanes, which enables the streamlined construction of a wide range of silicon-stereogenic silanes, is successfully developed. This process involves a SiH2-steered highly enantioselective C–H silylation to furnish the corresponding desymmetric monohydrosilanes, which are subsequently trapped with alkenes in a stereospecific fashion to build functionally diverse asymmetrically tetrasubstituted silanes. This general strategy combines readily available dihydrosilanes and alkenes to construct various enantioenriched silicon-stereogenic silanes, including 9-silafluorenes, Si-bridged ladder compounds, and benzosilolometallocenes, in a single step with good to excellent yields and enantioselectivities.

Simultaneous construction of axial and planar chirality by gold/TY-Phos-catalyzed asymmetric hydroarylation

“…And the simultaneous construction of two different types of chiralities is now flourishing development (Fig. 1b ) 44 – 51 .…”

Rhodium‐Catalyzed Synthesis of Chiral Monohydrosilanes by Intramolecular C−H Functionalization of Dihydrosilanes

“…The reaction involving unactivated C−H bonds are however much more demanding, since it requires harsher reaction conditions [9, 2u,v] due to the inert nature of the C−H bonds. This means that the monohydrosilanes could suffer a second C−H silylation, resulting in the undesired tetraorganosilanes as the thermodynamically favored products.…”

“…They very likely underwent an in situ Si−C bond formation in a stereospecific manner to afford the final tetraorganosilanes products. Very recently, He group reported two examples of intercepting the presumptive monohydrosilanes with alkenes [2u,v] . Again, only one monohydrosilane was reported in a low yield in the mechanistic study.…”

Enantioselective Construction of Six- and Seven-Membered Triorgano-Substituted Silicon-Stereogenic Heterocycles

“…With the continued interest in silicon-stereogenic chemistry, we questioned whether we could utilize asymmetric dehydrogenative C−H silylation toolbox 54,55 for the construction of six-or seven-membered silicon-stereogenic silanes. To achieve this target, three major obstacles are expected: 1) the intramolecular C−H silylation must proceed through a disfavoured seven-or eight-membered-ring cyclometallated intermediate, which would be rather challenging; 2) the competing dehydrogenative homo-coupling of dihydrosilanes is plausible 56,57 ; 3) the control of high enantioselectivity is elusive.…”