van der Boon Leon J P, Fuku-En Shin-Ichi, Slootweg J Chris, Lammertsma Koop, Ehlers Andreas W
1Department of Chemistry and Pharmaceutical Sciences, Faculty of Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
2Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8526 Japan.
Top Catal. 2018;61(7):674-684. doi: 10.1007/s11244-018-0967-5. Epub 2018 Apr 20.
Introducing chiral silicon centers was explored for the asymmetric Rh-catalyzed cyclization of dihydrosilanes to enantiomerically enriched spirosilanes as targets to enable access to enantiostable pentacoordinate silicates. The steric rigidity required in such systems demands the presence of two naphthyl or benzo[b]thiophene groups. The synthetic approach to the expanded spirosilanes extends Takai's method (Kuninobu et al. in Angew Chem Int Ed 52(5):1520-1522, 2013) for the synthesis of spirosilabifluorenes in which both a Si-H and a C-H bond of a dihydrosilane are activated by a rhodium catalyst. The expanded dihydrosilanes were obtained from halogenated aromatic precursors. Their asymmetric cyclization to the spirosilanes were conducted with [Rh(cod)Cl] in the presence of the chiral bidentate phosphane ligands (R)-BINAP, (R)-MeO-BIPHEP, and (R)-SEGPHOS, including derivatives with P-(3,5-t-Bu-4-MeO)-phenyl (DTBM) groups. The highest enantiomeric excess of 84% was obtained for 11,11'-spirobi[benzo[b]-naphtho[2,1-d]silole] with the DTBM-SEGPHOS ligand.
引入手性硅中心用于二氢硅烷的不对称铑催化环化反应，以对映体富集的螺硅烷为目标，从而能够获得对映体稳定的五配位硅酸盐。此类体系所需的空间刚性要求存在两个萘基或苯并[b]噻吩基团。扩展螺硅烷的合成方法扩展了高井的方法（Kuninobu等人，《德国应用化学》，52(5):1520 - 1522, 2013），用于合成螺硅双芴，其中二氢硅烷的Si - H和C - H键均由铑催化剂活化。扩展的二氢硅烷由卤代芳族前体获得。它们在手性双齿膦配体（R）- BINAP、（R）- MeO - BIPHEP和（R）- SEGPHOS存在下，用[Rh（cod）Cl]进行不对称环化反应生成螺硅烷，包括带有P -（3,5 - t - Bu - 4 - MeO）- 苯基（DTBM）基团的衍生物。使用DTBM - SEGPHOS配体时，11,11'-螺双[苯并[b]-萘并[2,1 - d]硅环戊二烯]的对映体过量最高可达84%。
