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Directed regioselective ortho,ortho′-magnesiations of aromatics and heterocycles using sBu2Mg in toluene†
Andreas Hess,Jan P. Prohaska,Sabrina B. Doerrich,Florian Trauner,Ferdinand H. Lutter,Sébastien Lemaire,Simon Wagschal,Konstantin Karaghiosoff,Paul Knochel
Chemical Science Pub Date : 05/18/2021 00:00:00 , DOI:10.1039/D1SC01777B
Abstract

Aryl azoles are ubiquitous as bioactive compounds and their regioselective functionalization is of utmost synthetic importance. Here, we report the development of a toluene-soluble dialkylmagnesium base sBu2Mg. This new reagent allows mild and regioselective ortho-magnesiations of various N-arylated pyrazoles and 1,2,3-triazoles as well as arenes bearing oxazoline, phosphorodiamidate or amide directing groups. The resulting diarylmagnesium reagents were further functionalized either by Pd-catalyzed arylation or by trapping reactions with a broad range of electrophiles (aldehydes, ketones, allylic halides, acyl chlorides, Weinreb amides, aryl halides, hydroxylamine benzoates, terminal alkynes). Furthermore, several double ortho,ortho′-magnesiations were realized in the case of aryl oxazolines, N-aryl pyrazoles as well as 2-aryl-2H-1,2,3-triazoles by simply repeating the magnesiation/electrophile trapping sequence allowing the preparation of valuable 1,2,3-functionalized arenes.

Graphical abstract: Directed regioselective ortho,ortho′-magnesiations of aromatics and heterocycles using sBu2Mg in toluene
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