References
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3 In the strongly coordinating solvent DMSO, the reagent was interpreted to be monomeric.
4 Both Orsini et al. (ref. 12) and Dekker et al. (ref. 2) clearly described that they failed to obtain the crystals of this reagent.
5 Bachmann WE.
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6 Picotin G.
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4796 ; in this report, ethyl bromoacetate was reacted with zinc in the presence of a carbonyl substrate and Et2 O was used as solvent
7 2 and 1,2-dibromoethane were also examined, but TMSCl was most preferable. Indeed when I2 was utilized for Zn activation in Et2 O, sometimes there was ‘an induction period’ and heating was needed for reaction to be initiated: Zitsman J.
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8 Metallic zinc ca. 96-97% (impurities: Pb, Cd, Fe), particle size 6 µm (average), Honjo Chemical Corporation.
9 Heat values calculated from the adiabatic reaction in a Dewar vessel were as follows: heat of reaction ΔH
m = 2.47 × 105 J/mol, adiabatic temperature increase ΔT
ad = 81 °C.
10 Figure
[4
Figure 4 Exothermic behavior in the preparation of ethyl bromozincacetate
11 Although we attempted to analyze impurities by an NMR study of the concentrated residue of the obtained ethyl bromozincacetate-THF solution, useful information could not be obtained due to residual THF and other complicated constituents; there was no trace of side products such as ethyl acetoacetate in the NMR spectrum of the isolated crystals. On the other hand, we observed molecular ion peaks of ethyl acetoacetate, diethyl succinate, and other unknown compounds in the GC-MS of the hydrolytically quenched THF soln; adequate GC methods for quantitative analysis of the reagent solution could not be set up.
12 Orsini F.
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13 The ethyl derivative was rotationally symmetric, while the tert -butyl derivative was point symmetric.
14 We have been concerned that the reactivity of the reagent itself, not its reactivity in slurry state, was inhibited by irreversible changes during crystallization. However, there were no problems with this crystalline reagent.
15 Kawakami J.
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16 Even when these solutions were concentrated, crystallization did not occur. On the other hand, the crystallization could not be prevented when DME or another solvent was added after preparing the reagent as the THF solution.
17 Kawakami J, Nakamoto K, Nuwa S, Handa S, and Miki S. inventors; WO 2003059889. We have submitted an international patent application on the present work:
18 The crystallographic data have been deposited at the Cambridge Crystallographic Data Center; deposition number CCDC 656586.
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