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

Abstract

The preparation of chiral monohydrosilanes remains a rarely achieved goal. To this end a Rh‐catalyzed desymmetrization of dihydrosilanes by way of intramolecular C(sp2)−H functionalization under simple and mild conditions has now been developed. This method provides easy access to a broad range of chiral monohydrosilanes in good yields with excellent enantioselectivities (up to >99 % ee). The resulting monohydrosilanes constitute a good platform to access stereogenic silicon compounds, as well as useful compounds to probe silicon stereochemistry.

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

“…Thea bsolute configuration of 2am was determined to be S based on single-crystal X-ray analysis (Scheme S1 in SI). [11] Isopropyl-Si substrates bearing substituents on both the A and the B rings were also compatible with the optimized reaction conditions (Scheme 3). In general, having substituents on both rings decreased the yields and enantioselectivities.Such an impact was very pronounced in the cases of 2ba, 2bh and 2bk.…”

“…We also examined the ferrocene substrates with Fsubstitutions on the A ring (e.g., 2el, 2em and 2en), which showed that the substitution on A ring were well tolerated with different alkyl-Si patterns.I tw as thus clear that our method should work well on various type of ferrocene substrates.T he absolute configuration of the product 2eg was determined to be RIS Si, R p according to single-crystal Xray analysis (Scheme S3 in SI). [11] Taken together, the reaction scope studies have demonstrated that our method can produce aw ide variety of chiral monohydrosilanes.T he reaction worked well on bi-phenyl skeletons,t olerating many types of substitution patterns on either phenyl ring or on the bi-phenyls (Scheme 2and 3). The substitutions the Si could be selected from at least 7different alkyl groups (Scheme 4).…”

“…Thechlorine in 2bh was seemingly smaller than iso-propyl group,yet it gave the lowest ee among all the cases.The absolute configuration of 2bn was assigned as R by single-crystal X-ray analysis of the corresponding derivative compound 8 (Scheme S2 in SI). [11] We showed that other alkyl substitutions on the Si atoms were also well tolerated (Scheme 4). Ethyl-Si substrates (i.e., 2ca, 2ce, 2ci, 2cm, 2cq and 2cu)g ave good yields.T he enantioselectivities were comparable to those of isopropyl-Si substrates,except that 2cu saw adrastic decrease in enantioselectivity.…”

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

“…Early this year, the asymmetric synthesis of chiral monohydrosilanes via Rh-catalyzed intramolecular CÀ H silylation approach has been finally realized by the group of W. He. [20] Using a combination of [Rh(COD)Cl] 2 and (R)-DTBM-Segphos (L6), a wide range of silicon-stereogenic spirosilabifluorenecored and ferrocene-based monohydrosilanes were readily obtained in high yields and excellent enantioselectivities under mild conditions (Scheme 7). Gratifyingly, silicon-stereogenic spirosilabifluorene-cored tetrasubstituted silanes could be obtained via stereospecific transformations of the SiÀ H bond, including alcoholysis with alcohol, hydrosilylation with ketone, alkene and alkyne, and dehydrogenative arylation with arene.…”

“…Early this year, the asymmetric synthesis of chiral monohydrosilanes via Rh‐catalyzed intramolecular C−H silylation approach has been finally realized by the group of W. He [20] . Using a combination of [Rh(COD)Cl] 2 and ( R )‐DTBM‐Segphos ( L6 ), a wide range of silicon‐stereogenic spirosilabifluorene‐cored and ferrocene‐based monohydrosilanes were readily obtained in high yields and excellent enantioselectivities under mild conditions (Scheme 7).…”