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

Abstract

We report highly enantioselective intra-molecular, silylations of unactivated, primary C(sp3)–H bonds. The reactions form dihydrobenzosiloles in high yields with excellent enantioselectivities by functionalization of enantiotopic methyl groups under mild conditions. The reaction is catalyzed by an iridium complex generated from [Ir(COD)OMe]2 and chiral dinitrogen ligands that we recently disclosed. The C–Si bonds in the enantio-enriched dihydrobenzosiloles were further transformed to C–Cl, C–Br, C–I, and C–O bonds in final products. The potential of this reaction was illustrated by sequential C(sp3)–H and C(sp2)–H silylations and functionalizations, as well as diastereoselective C–H silylations of a chiral, natural-product derivative containing multiple types of C–H bonds. Preliminary mechanistic studies suggest that C–H cleavage is the rate-determining step.

Iridium‐Catalyzed, Silyl‐Directed, peri‐Borylation of C−H Bonds in Fused Polycyclic Arenes and Heteroarenes

“…The C−Si bond in compound 6 was oxidized to the C−O bond in naphthol 12 when treated with a combination of hydrogen peroxide, base and fluoride. Halogenation of the C−Si bond in 6 with NXS (X=Br and Cl) and AgF occurred smoothly to give products 13 and 14 in 71 % and 65 % yields, respectively . The C−Si bond also was converted to a C−C bond in the 1,8‐diarylnaphthalene by palladium‐catalyzed coupling (Scheme ) …”

Iridium-catalyzed silylation of unactivated C–H bonds

“…Oxidation under Tamao-Fleming conditions generates the amino alcohol during a process in which the bridging methylene unit is presumably extruded as Scheme 12. Ir-catalyzed hydrosilyl-directed silylation of enantiotopic methyl CeH bonds yields enantiopure products and can be applied to complex molecule scaffolds [35].…”

Functionalization of a Single C−F Bond of Trifluoromethylarenes Assisted by an ortho‐Silyl Group Using a Trityl‐Based All‐in‐One Reagent with Ytterbium Triflate Catalyst

“…[9] Desilylhalogenations using Nhalosuccinimides (NXS, X = Cl, Br,a nd I) efficiently proceeded to provide 11 a-c without damaging the arylthioa nd difluoromethylene groups. [10] Since aw ide varietyo fa ryl trityl sulfides and benzotrifluorides couldb ep repared by the modular synthesis combining easily available startingm aterials, the selectiveC ÀFt hiolation allows for the synthesis of diverse aryl difluorobenzyl sulfides from simple modules.F or example, we accomplished the synthesis of benzotrifluoride 13 from 12 a,t rifluoromethylsilane, and chlorodiphenylsilane, via the iodotrifluoromethylation of aryne intermediate III ( Figure 4B). [11,12] Aryl trityl sulfide 14 was also prepared from simple modules, 12 b,a na ryl iodide, and triphenylmethanethiol, via the CÀHb orylation followed by the Suzuki-Miyaura cross-coupling reactiona nd subsequent addition reaction using the thiol to aryne intermediate IV.…”