[631-22-1] · C7H10Br2O4 · Diethyl Dibromomalonate · (MW 317.96)
Alternate Name: ethyl dibromomalonate.
Physical Data: bp 108-110 °C/4 mmHg.
Solubility: sol benzene, CCl4, DMSO, THF.
Form Supplied in: commercially available in 98% purity as a liquid.
Analysis of Reagent Purity: NMR, combustion analysis.
Purification: distillation at reduced pressure.
Handling, Storage, and Precautions: lachrymator; light sensitive. Store in the dark under nitrogen. This toxic reagent should be handled in a fume hood.
Esters can be selectively a-brominated by reaction of this reagent with the lithium enolate at -78 °C (eqs 1 and 2). The esters can then be converted to the corresponding carboxylic acids.1,3 This bromination can be carried out on substrates bearing remote alkenic functionality. Bromination of the lithium enolate in eq 1 using Br2 at -78 °C gave a poor yield of a-brominated ester.
Alkenes can be cyclopropanated in a nonstereospecific fashion by treatment with diethyl dibromomalonate in the presence of Copper powder or Copper(I) Bromide.4 Higher yields are obtained when this reaction is run in DMSO (eq 3). The yield of cyclopropane product is highly dependent on the amount of copper used. Tetraethyl ethylenetetracarboxylate is commonly observed as a side-product in this transformation.
Nonstereospecific cyclopropanation of Michael acceptors can be accomplished by use of this reagent in combination with Tri-n-butylstibine (eq 4)5 or indium.6 Carbonyl groups can also react with diethyl dibromomalonate in the presence of tri-n-butylstibine to form alkenes.7
George D. Maynard
Marion Merrell Dow, Cincinnati, OH, USA