Synthesis 2007(17): 2746-2750  
DOI: 10.1055/s-2007-983780
PSP
© Georg Thieme Verlag Stuttgart · New York

Practical Chloromanganese-Salen-Catalyzed Enantioselective Reformatsky Reaction with Ketones

Pier Giorgio Cozzi*, Alessandro Mignogna , Luca Zoli
Dipartimento di Chimica ‘G. Ciamician’, University of Bologna, Via Selmi 2, 40126 Bologna, Italy
Fax: +39(051)2099456; e-Mail: [email protected];
Further Information

Publication History

Received 12 February 2007
Publication Date:
12 July 2007 (online)

Abstract

The first catalytic enantioselective Reformatsky reaction is realized by a controlled transmetalation of an α-iodo ester with di­methylzinc in the presence of a chloromanganese-Salen complex (20 mol%) as catalyst and 4-phenylpyridine N-oxide (25 mol%) as additive. The zinc enolate is formed under mild conditions at room temperature; it undergoes enantioselective addition to ketones. The reaction shows broad scope and moderate to good stereoselection and it allows the straightforward preparation of quaternary stereogenic centers.

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9

Cozzi P. G., unpublished results.

19

The combination of ClMn(Salen) with Me2Zn, in the absence of iodoacetate and ketones, gives a rapid development of a yellow color, indicating the presence of Zn(Salen). In addition, by quenching the reaction with water, free Salen ligand is observed by TLC analysis. ClMn(Salen) is quite stable in the presence of water.