- Rational tuning chelate size of bis-oxazoline ligands to improve enantioselectivity in the asymmetric aziridination of chalcones
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Chalcones were asymmetrically aziridinated with [N-(p-toluenesulfonyl) imino]phenyliodinane (PhI=NTs) as a nitrene source under catalysis of CuOTf and a series of cyclohexane-linked bis-oxazolines (cHBOXes), which are chelate size rationally tuned bis-oxazolines. The results indicate that highly enantioselective aziridination of chalcones with up to >99% ee have been achieved under catalysis of (S,S)-1,2-bis[(S)-(4-phenyl)oxazolin-2-yl] cyclohexane, which is the most-matched stereoisomer among cyclohexane-linked bis-oxazolines. It was also found that the enantioselectivity is not substituent-dependent with respect to chalcones in the present case, unlike with 1,8-anthracene-linked bis-oxazolines (AnBOXes).
- Ma, Linge,Du, Da-Ming,Xu, Jiaxi
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p. 10155 - 10158
(2007/10/03)
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- Intramolecular Cooperative Reactions of 1,2-Bis(diazoketone)s. The First Syntheses of trans-Hydro-1H-2-inden-1-ones
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The intramolecular cooperative reactions of 1,2-bis(diazoketone)s initiated by the Wolff rearrangement of α-diazoketones have been investigated.Under thermal conditions, 1,2-bis(diazoketone)s are efficiently transformed into 2-cyclopenten-1-one derivatives with complete stereospecificity.Thus, a most extraordinary result is reported, that trans-hydro-2-inden-1-ones (1-3) were synthesized for the first time from trans-1,2-bis(diazoketone)s (5, 11, and 12), respectively.The unprecedented trans-hydroindenone structure was confirmed by X-ray analysis of 3 as well as 1H NMR analysis and was supported by ab initio molecular orbital calculations.The same reactions were also carried out under photochemical conditions and were applied to 1,3-bis(diazoketone)s, giving 2-cyclohexen-1-one derivatives.
- Nakatani, Kazuhiko,Takada, Kazunori,Isoe, Sachihiko
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p. 2466 - 2473
(2007/10/02)
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