Enantioconvergent Hydroboration of a Racemic Allene: Enantioselective Synthesis of (E)-δ-Stannyl-anti-homoallylic Alcohols via Aldehyde Crotylboration
摘要:
The enantioconvergent hydroboration of racemic allenylstannane (+/-)-1 with ((d)Ipc)(2)BH converts both enantiomers of (+/-)-1 into the enantioenriched crotylborane (S)-E-3. Subsequent crotylboration of aldehydes with (S)-E-3 provides (E)-stannyl-homoallylic alcohols 5 in good yields and with excellent enantioselectivity.
Chiral sulfoxides as activators of allyl trichlorosilanes in the stereoselective allylation of aldehydes
作者:Vincenzo De Sio、Antonio Massa、Arrigo Scettri
DOI:10.1039/c002988b
日期:——
Chiral aryl methyl sulfoxides proved to be efficient activators in the asymmetric allylation of aldehydes with allyl trichlorosilanes. High enantioselectivity was found in the case of electron-poor aldehydes. The high levels of diastereoselectivity and the detection of nonlinear effects have allowed the elucidation of some mechanistic aspects of the reaction.
terminal alkenes catalysed by (R,R)-ethylene-1,2-bis(η5-4,5,6,7-tetrahydro-1-indenyl)zirconium(R)-1,1′-binaphth-2,2′-diolate gave low turnovers and enantioexcesses. A novel Ci symmetric zirconocene dichloride CpCp′ZrCl2 (Cp = C5H5, Cp′ = 1-neomenthyl-4,5,6,7-tetrahydroindenyl) was prepared which gave better enantioselectivity, is cheaper to make, catalytically more active, and recoverable.
通过催化末端烯烃的ethylmagnesiation([R ,- [R )-亚乙基-1,2-双(η 5 -4,5,6,7-四氢-1-茚基)合锆([R)-1,1'- binaphth- 2,2'-羟乙酸盐产生较低的营业额和对映体过量。制备了一种新的C i对称的二茂锆锆CpCp'ZrCl 2(Cp = C 5 H 5,Cp'= 1-新薄荷基-4,5,6,7-四氢茚基),该对映体具有更好的对映选择性,制造成本更低,催化作用更多。活跃且可恢复。
Zirconocene-catalyzed kinetic resolution of dihydrofurans
作者:Michael S. Visser、Amir H. Hoveyda
DOI:10.1016/0040-4020(94)01127-l
日期:1995.4
Zisconocene-catalyzed kinetic resolution of dihydrofurans may be effected in the presence of 10 mol% non-racemic (EBTHI)ZrCl2. Transformations reported herein proceed efficiently to afford two constitutionally distinct and readily separable products with excellent levels of diastereo- and enantioselectivity. Preparation and resolution of the substrate furans may be carried out in a single pot.