Synlett 2009(15): 2545-2546  
DOI: 10.1055/s-0029-1217801
SPOTLIGHT
© Georg Thieme Verlag Stuttgart ˙ New York

Lombardo’s Reagent

Hemender R. Chand*
Division of Organic Chemistry, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India.
e-Mail: h.chand@ncl.res.in;
Further Information

Publication History

Publication Date:
27 August 2009 (online)

Introduction

The reagent combination Zn/CH2Br2/TiCl4 gives rise to an organometallic reagent which is known as Lombardo’s reagent. It converts ketones into methylene groups. [¹] The active reagent is presumed to be a dimetalated species (1) which adds to the ketone under the influence of the Lewis acidity of titanium to give a β-oxymetal-substituted organometallic compound (2). Following β-elimination generates the methylene group (3) [²] (Scheme  [¹] ).

Ketones are not enolized by the reagent and as an important consequence adjacent enolizable chiral centers are not epimerized. The reagent is compatible with a wide ­variety of functional groups, e.g., THP and tert-butyldi­methylsilyl ethers, acetals, esters, carboxylic acids, alcohols, and lactones. [³] Such selectivity makes it a valuable procedure in organic synthesis and appreciably augments Wittig methodology.

    References

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