Hydroxylic additives enhance yield and scalability of silicon-directed Nazarov reaction

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• 作者：Shaon Joy ; Waka Nakanishi ; F.G. West
• 关键词：Nazarov cyclization ; Silicon-directed ; Cyclopentenones ; Additive effects ; Lewis acid-assisted Br&oslash ; nsted acid
• 刊名：Tetrahedron Letters
• 出版年：2013
• 出版时间：9 October, 2013
• 年：2013
• 卷：54
• 期：41
• 页码：5573-5576
• 全文大小：640 K

文摘

As a result of difficulties in scaling up silicon-directed Nazarov cyclization for use in the synthesis of taxane natural products, the effect of additives was examined. Hydroxylic additives were found to convey a consistent beneficial effect on the rate, overall yield, and scalability of these reactions. Optimal conditions (1.5 equiv methanol or water with substoichiometric FeCl₃), were successfully applied to a range of ¦Â-silyl dienone substrates, including several complex polycyclic examples, as well as simpler dienones previously shown to be low-yielding or completely unreactive under the conventional conditions.