Rhodium‐Catalyzed Asymmetric Synthesis of Spirosilabifluorene Derivatives

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

“…[19] When the less hindered Spirophos (S)-L1 (Zhou) [20] was used, alow conversion (51 %) and am arginal ee value (9 %) were obtained, with ac onsiderable amount of desilylation product (2aa/3aa=5:1; entry 2). In the case of (S)-BINAP (L2;K uninobu and Takais optimal ligand), [16] the conversion was increased to 97 %at1 00 8 8Cbut the enantioselectivity was low (À22 % ee; entry 3). This lower enantioselectivity,c ompared to that reported by Kuninobu, Takai, and co-workers (81 % ee) substantiated the mechanistic difference between these two reactions.…”

Desymmetrization‐Oriented Enantioselective Synthesis of Silicon‐Stereogenic Silanes by Palladium‐Catalyzed C−H Olefinations

“…Undoubtedly,i ti sr ecognized as ac hallenge in the field of CÀHa ctivation to develop highly enantioselective catalytic methods towardc hiral silanes because trigonal silicon is too unstable for synthetic transformations [6] and many CÀHa ctivation reactions requireh arsh conditions. In fact, only intramolecular CÀHb ond functionalization approaches have been reportedt oa ccess cyclic siliconstereogenic silanes such as dibenzosiloles and 5,10-dihydrophenazasiline, including the direct arylation, [7] dehydrogenative silylation, [8] 1,5-palladium migration reaction, [9] and ring expansion/dehydrogenative silylation [10] reactions. The pioneering work by the group of Gevorgyan showedt hat pyridine and pyrimidine serve as powerful directing groups in various CÀH functionalization reactions of silicon-tethered arenes [11] (Scheme 1).…”

Silylations of Arenes with Hydrosilanes: From Transition‐Metal‐Catalyzed CX Bond Cleavage to Environmentally Benign Transition‐Metal‐Free CH Bond Activation

“…In 2011, Scheme1.Previousreports on the palladium-catalyzed silylation of aryl halides with hydrosilane. [21] ChemSusChem 2015, 8,2176 -2179 www.chemsuschem.org Oestreich et al [24] established an ovel catalytic system for the direct CÀHs ilylation of N-methyl indoles, in which they disclosed ap erfectly regioselective and mild silylation of indoles. [19] Scheme3.Synthesis of silicon-stereogenic spirosilabifluorene derivatives 10 through catalytic silylation by CÀHa nd SiÀHa ctivation.…”

“…In this regard, as triking example was reported by Kuninobu and co-workersi n2 013. [21] They demonstrated an atom-economical synthesis of aq uaternary silicon-containing spirosilabifluorene derivative 10 from bis(biphenyl)silane 9 by double dehydrogenative silylation using ar hodium catalyst. More importantly,t he authors succeeded in the synthesis of silicon-stereogenic spirosilabifluorene derivatives 10 a-e with good enantioselectivity (Scheme 3, up to 81 % ee), also confirming the powerful potential of catalytic silylation of arenes with hydrosilanes in chiral synthesis.…”

“…[19] Scheme3.Synthesis of silicon-stereogenic spirosilabifluorene derivatives 10 through catalytic silylation by CÀHa nd SiÀHa ctivation. [21] ChemSusChem 2015, 8,2176 -2179 www.chemsuschem.org Oestreich et al [24] established an ovel catalytic system for the direct CÀHs ilylation of N-methyl indoles, in which they disclosed ap erfectly regioselective and mild silylation of indoles. It was found that N-methyl indoles 11 with electron-donating and withdrawing groups led to the corresponding C3-selective products 13 in good to excellent yields (Scheme 4).…”