The first isolation of crystalline ethyl bromozincacetate, typical Reformatsky reagent: Crystal structure and convenient preparation

The highly reproducible preparation of ethyl bromozincacetate was achieved by a convenient procedure in which an excess amount of zinc powder was subjected to activation by chlorotrimethylsilane, followed by dropwise addition of ethyl bromoacetate. From the resultant solution of this Reformatsky reagent, crystalline ethyl bromozincacetate was isolated and its crystal structure was elucidated as its tetrahydrofuran-coordinated dimer (BrZnCH(2)CO(2)Et center dot THF)(2) by X-ray crystal structure analysis. Although it had a dimeric structure similar to the tert-butyl bromozincacetate crystal, the two had different stereochemistry in the zinc-containing eight-membered ring (ZnCH(2)CO)(2). The crystalline reagent obtained possessed satisfactory reactivity and stability for practical use. On the other hand, by preparing the tetrahydrofuran-free ethyl bromozincacetate in such solvents as 1,2-dimethoxy-ethane or cyclopentyl methyl ether, unintended crystallization could be successfully prevented.