Synthesis 2005(15): 2625-2629  
DOI: 10.1055/s-2005-872097
PSP
© Georg Thieme Verlag Stuttgart · New York

Preparation and Reactions of Highly Functionalized Bis-Arylzinc Reagents Using a Li(acac)-Catalyzed Iodine-Zinc Exchange

Florian F. Kneisel, Helena Leuser, Paul Knochel*
Ludwig-Maximilians-Universität München, Department Chemie und Biochemie, Butenandtstrasse 5-13, Haus F, 81377 München, Germany
Fax: +49(89)218077680; e-Mail: paul.knochel@cup.uni-muenchen.de;
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Publikationsverlauf

Received 16 June 2005
Publikationsdatum:
22. Juli 2005 (online)

Abstract

Polyfunctional bis-arylzinc reagents are accessible via a new lithium acetylacetonate-catalyzed iodine-zinc exchange. This protocol tolerates sensitive functional groups (ketones, aldehydes or isothiocyanates) in the aryl iodides and allows the formation of highly functionalized zinc reagents. These zinc reagents can be used in a variety of catalyzed and uncatalyzed transformations.

18

The exact determination of all the concentrations of the solutions used (s-BuLi, ZnCl2, s-Bu2Zn) is decisive for the success of this procedure. Threefold titration and averaging have been typically done.

19

The complete absence of LiCl is decisive for the success of the iodine-zinc exchange procedure.

20

Threefold titration has been performed.

21

Prepared by acylation of 4-hydroxy-3,5-diiodobenzoate with Ac2O (1.3 equiv) in pyridine in the presence of DMAP (0.1 equiv).