“On Water” Organocatalyzed [4 + 2] Cycloaddition of Enones and Nitro Dienes for the Enantioselective Synthesis of Densely Substituted Cyclohexanones

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• 作者：Ganga B. Vamisetti ; Raghunath Chowdhury ; Mukesh Kumar ; Sunil K. Ghosh
• 刊名：Organic Letters
• 出版年：2016
• 出版时间：May 6, 2016
• 年：2016
• 卷：18
• 期：9
• 页码：1964-1967
• 全文大小：368K
• 年卷期：0
• ISSN：1523-7052

文摘

An “on water” hydroquinine-based primary amine–benzoic acid organocatalyst system was found to be best suited to produce 3,4,5-trisubstituted cyclohexanones with a nitro group in the 4-position from enones and nitro dienes under ambient conditions in good yield, with good diastereoselectivity, and with excellent enantioselectivity. An appreciable rate enhancement by water was observed compared to organic solvents. Mechanistic analysis of the reaction suggests that it followed an endo [4 + 2] cycloaddition with enamine of enone as diene and nitro diene as dienophile.