Enantiomerically Pure Axially Chiral Aminocarbene Complexes of Chromium
详细信息 查看全文
- 作者：Ludě ; k Meca ; Ivana Cí ; sař ; ová ; Duš ; an Drahoň ; ovský ; Dalimil Dvoř ; á ; k
- 刊名：Organometallics
- 出版年：2008
- 出版时间：April 28, 2008
- 年：2008
- 卷：27
- 期：8
- 页码：1850 - 1858
- 全文大小：467K
- 年卷期：v.27,no.8(April 28, 2008)
- ISSN：1520-6041
文摘
Aminocarbene complexes having a methyl group in the ortho-position to the aminocarbene moiety on the aromatic ring, (S)-pentacarbonyl[(N,N-dimethylamino)(3-methoxycarbonyl-2-methylphenyl)carbene]chromium(0) [(S)-6] and (R)-pentacarbonyl[(N,N-dimethylamino)(5-methoxycarbonyl-2-methylphenyl)carbene]chromium(0) [(R)-7], were prepared in enantiomerically pure form by the crystallization of diastereoisomeric esters with (S)-1-(1-naphthyl)ethanol. In the case of (S)-6 the racemization barrier ΔG
rac = 121 ± 0.5 kJ·mol−1 was established. The substitution of o-methyl group with an isopropyl group virtually did not change the racemization barrier (ΔGrac = 120.5 ± 0.5 kJ·mol−1), while the introduction of an o-phenyl group led to substantial lowering of ΔGrac. Attempts to transfer chirality in thermal reactions of the complexes (S)-6 and (R)-7 with alkynes, palladium-catalyzed insertion into a C−H bond, and photochemical formation of β-lactams were unsuccessful.
rac = 121 ± 0.5 kJ·mol−1 was established. The substitution of o-methyl group with an isopropyl group virtually did not change the racemization barrier (ΔGrac = 120.5 ± 0.5 kJ·mol−1), while the introduction of an o-phenyl group led to substantial lowering of ΔGrac. Attempts to transfer chirality in thermal reactions of the complexes (S)-6 and (R)-7 with alkynes, palladium-catalyzed insertion into a C−H bond, and photochemical formation of β-lactams were unsuccessful.