Construction of a Chiral Silicon Center by Rhodium‐Catalyzed Enantioselective Intramolecular Hydrosilylation

Abstract

Rhodium-catalyzed enantioselective desymmetrizing intramolecular hydrosilylation of symmetrically disubstituted hydrosilanes is described. The original axially chiral phenanthroline ligand (S)-BinThro (Binol-derived phenanthroline) was found to work as an effective chiral catalyst for this transformation. A chiral silicon stereogenic center is one of the chiral motifs gaining much attention in asymmetric syntheses and the present protocol provides cyclic five-membered organosilanes incorporating chiral silicon centers with high enantioselectivities (up to 91 % ee). The putative active Rh(I) catalyst takes the form of an N,N,O-tridentate coordination complex, as determined by several complementary experiments.

Construction of Chiral Tetraorganosilicons by Tandem Desymmetrization of Silacyclobutanes/Intermolecular Dehydrogenative Silylation

“…[6] This simple fact has av ery clear conceptual consequence:s tereogenic silicons must come from tetrasubstituted silicon precursors.I ti st herefore not surprising that the catalytic construction of chiral silicons exclusively depends on desymmetrization of prochiral silicons.I nt his context, an umber of prochiral silicons have been explored. Dihydrosilanes are the most common precursors owing to their versatile reactivity and wide availability.D esymmetrization based on the signature hydrosilylation reaction of alkynes, [7] ketones, [8] and alkenes [9] has been reported. Carbene insertion [10] and alcoholysis [11] are also very efficient and highly enantioselective.T he more challenging cross-coupling reaction with aryl iodide has been described.…”

Construction of Chiral Tetraorganosilicons by Tandem Desymmetrization of Silacyclobutanes/Intermolecular Dehydrogenative Silylation

“…[4] Aside from the different bonding behavior of silicon, the general lack of strategies to construct silicon stereogenic centers could be understood by the fact that chiral carbon centers are often accessed by asymmetric addition to sp 2hybridized carbons,w hereas sp 2 -hybridized silicons are not stable. Dihydrosilanes are the most common precursors owing to their versatile reactivity and wide availability.D esymmetrization based on the signature hydrosilylation reaction of alkynes, [7] ketones, [8] and alkenes [9] has been reported. Dihydrosilanes are the most common precursors owing to their versatile reactivity and wide availability.D esymmetrization based on the signature hydrosilylation reaction of alkynes, [7] ketones, [8] and alkenes [9] has been reported.…”

Renovation of Optically Active Phenanthrolines as Powerful Chiral Ligands for Versatile Asymmetric Metal Catalysis

“…The design of ( S )‐ 1 is based on the concept of renovation of optically active phen derivatives as chiral ligands efficient for versatile asymmetric metal catalysis. Our endeavor to develop enantioselective transformations has been devoted to several enantioselective reactions such as (i) addition of organozinc reagents to aldehydes,11 (ii) Zn(II)‐catalyzed electrophilic amination of β‐ketoesters with azodicarboxylate,21 (iii) Cu(II)‐catalyzed α‐hydroxylation of oxindole derivatives,26 (iv) Ni(II)‐catalyzed Michael addition of oxindole derivatives to MVK,27 and (v) Rh(I)‐catalyzed intramolecular hydrosilylation for the construction of chiral silicon stereogenic centers 30. Further applications using other metal catalysts are ongoing to broaden the utility of ( S )‐ 1 .…”

“…In this chapter, we discuss the Rh‐catalyzed enantioselective desymmetrization of hydrosilanes towards the construction of chiral silicon stereogenic centers,29 which have been of great interest considering their unique chemical and physical properties. In this context, the aim of our synthetic plan is the utilization of the enantioselective desymmetrization of prochiral silanes 19 via intramolecular hydrosilylation in the presence of a chiral transition‐metal catalyst, thus giving chiral silicon‐containing olefins 20 (Scheme ) 30. A few examples of the catalytic asymmetric preparation of chiral silicon compounds utilizing hydrosilylation protocols were reported by Tamao and Tomooka 31…”