Telescoped Flow Process for the Syntheses of N-Aryl Pyrazoles
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- 作者：Bryan Li ; Daniel Widlicka ; Steven Boucher ; Cheryl Hayward ; John Lucas ; John C. Murray ; Brian T. O鈥橬eil ; David Pfisterer ; Lacey Samp ; John VanAlsten ; Yanqiao Xiang ; Joseph Young
- 刊名：Organic Process Research & Development
- 出版年：2012
- 出版时间：December 21, 2012
- 年：2012
- 卷：16
- 期：12
- 页码：2031-2035
- 全文大小：280K
- 年卷期：v.16,no.12(December 21, 2012)
- ISSN：1520-586X
文摘
N-Aryl pyrazoles were prepared from anilines in a three step telescoped approach. An aniline was diazotized to give the diazonium fluoroborate, followed by reduction with tin(II) chloride to give the corresponding hydrazine, which in turn reacted with a ketoenamine to give the N-aryl pyrazole. The deprotection of the methyl ether was accomplished with PhBCl2 to give the final product. The continuous flow methodology was used to minimize accumulation of the highly energetic and potentially explosive diazonium salt and hydrazine intermediates to enable the safe scale-up of N-aryl pyrazoles. The heterogeneous reaction mixture was successfully handled in both lab scale and production scale. A continuous extraction was employed to remove organic impurities from the diazotization step, which eliminated the need for chromatography in the purification of the final N-aryl pyrazole.