Highly enantioselective aldol reactions using a tropos dibenz[c,e]azepine organocatalyst |
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Authors: | Barry Lygo Christopher DavisonTimothy Evans James AR GilksJohn Leonard Claude-Eric Roy |
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Institution: | a School of Chemistry, University of Nottingham, Nottingham NG7 2RD, UK b AstraZeneca, Silk Business Park, Macclesfield, Cheshire SK10 2NA, UK |
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Abstract: | The four-step synthesis of a chiral primary tertiary diamine salt, possessing a tropos dibenzc,e]azepine ring is described. It is shown that 3.5-5 mol % of this salt is capable of promoting highly enantioselective crossed-aldol reactions between cyclohexanone and a series of aromatic aldehydes. In all cases, the aldol reactions proceed with high diastereoselectivity for the anti-aldol product. The outcome of crossed-aldol reactions involving other cyclic ketones and acyclic ketones are also described. All examples involving cyclic ketones result in selectivity for the anti-aldol products, whereas acyclic ketones were found to favour the syn-aldol products. A discussion on the role of the chiral primary tertiary diamine salt in the catalysis of the aldol reactions is also presented. |
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Keywords: | Asymmetric catalysis Aldol Organocatalysis Diamine Stereoselective |
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