Palladium-Catalyzed Enantioselective Desymmetrization of Silacyclobutanes: Construction of Silacycles Possessing a Tetraorganosilicon Stereocenter

Abstract

A palladium-catalyzed desymmetrization of alkyne-tethered silacyclobutanes to give silacycles possessing a tetraorganosilicon stereocenter has been developed, and high chemo- and enantioselectivities have been achieved by the use of a newly synthesized chiral phosphoramidite ligand.

Rhodium‐Catalyzed Reaction of Silacyclobutanes with Unactivated Alkynes to Afford Silacyclohexenes

“…[7,8] To the best of our knowledge,o nly Shintani and Hayashi have succeeded in forming silacyclohexenes,for which they used an intramolecular approach involving an aryl-substituted alkyne and aSCB tethered by aphenyl ring. [11] Therefore,itwould be beneficial to develop general processes that generate silacyclohexenes intermolecularly from unactivated alkynes and SCBs.S uch approaches would largely expand the structural diversity of the resulting silacyclohexenes.Here we report such areaction in the presence of Rh catalyst that generates silacyclohexenes with high chemoselectivity.The good enantioselectivity at the stereogenic silicon center was also achieved using an ewly synthesized chiral phosphoramidite ligand.…”

Illuminating the Mechanism of the Borane‐Catalyzed Hydrosilylation of Imines with Both an Axially Chiral Borane and Silane

“…151–152 °C (cyclohexane); R f =0.14 (cyclohexane); GLC (HP‐5): t R =44.1 min; [ α ]${{{20\hfill \atop {\rm D}\hfill}}}$ =+71.0 ( c =0.58, CHCl 3 ); 1 H NMR (500 MHz, CDCl 3 ): δ =2.25 (d, AB spin system, 2 J =13.6 Hz, 1 H), 2.28 (dd, AB spin system, 2 J =13.3 Hz, 3 J =7.1 Hz, 1 H), 2.31 (dd, AB spin system, 2 J =13.6 Hz, 3 J =2.3 Hz, 1 H), 2.36 (dd, AB spin system, 2 J =13.3 Hz, 3 J =2.1 Hz, 1 H), 4.69 (ddd, 3 J =7.1 Hz, 3 J =2.3 Hz, 3 J =2.1 Hz, 1 H), 7.13 (dm, 3 J =8.5 Hz, 1 H), 7.17 (dm, 3 J =8.7 Hz, 1 H), 7.18–7.24 (m, 2 H), 7.30–7.35 (m, 3 H), 7.37–7.43 (m, 5 H), 7.55 (d, 3 J =8.4 Hz, 1 H), 7.84 (d, 3 J =8.2 Hz, 1 H), 7.89–7.94 ppm (m, 3 H); 13 C NMR (126 MHz, CDCl 3 ): δ =20.37, 20.42, 124.6, 126.0, 126.1, 126.48, 126.53, 127.7, 128.1 (2 C), 128.19, 128.21, 128.3 (2 C), 130.1, 132.1, 132.2, 132.6, 132.7, 132.8, 132.9, 134.0, 134.7, 135.6, 136.0 ppm; 29 Si NMR (99 MHz, CDCl 3 ): δ =−2.0 ppm; IR (ATR): $\tilde \nu $ =3056 (m), 2130 (s), 1618 (m), 1592 (m), 1507 (s), 1427 (m), 1404 (m), 1355 (m), 1327 (m), 1242 (m), 1141 (s), 1112 (s), 1024 (m), 964 (s), 925 (m), 836 (s), 815 (s), 737 (s), 693 cm −1 (s); HRMS (EI): m / z : calcd for C 28 H 22 Si [ M + ]: 386.14853; found: 386.14918. According to the protodesilylation reported by Hayashi and Shintani et al.,22 TfOH (0.17 mL, 1.9 mmol, 3.5 equiv) was added to a solution of ( S )‐4‐phenyl‐4,5‐dihydro‐3 H ‐dinaphtho[2,1‐ c :1′,2′‐ e ]silepine (210 mg, 0.543 mmol, 1.00 equiv) in CH 2 Cl 2 (15 mL), and the mixture was stirred at room temperature. After 1 h, all volatiles were removed under full vacuum, and the residue was dissolved in CH 2 Cl 2 (5 mL) and again subjected to full vacuum for 30 min.…”

Übergangsmetallkomplex‐katalysierte Desymmetrisierung: enantioselektiver Aufbau von Silanen mit Silicium‐Stereozentrum

“…[6] [7][8][9][10] 2011 beschrieb diese Arbeitsgruppe die Entwicklung eines chiralen Palladiumkatalysators zur enantioselektiven Desymmetrisierung von Silacyclobutanen zu Silacyclen mit Si-Stereozentrum. [6] [7][8][9][10] 2011 beschrieb diese Arbeitsgruppe die Entwicklung eines chiralen Palladiumkatalysators zur enantioselektiven Desymmetrisierung von Silacyclobutanen zu Silacyclen mit Si-Stereozentrum.…”