1,2-Dibromoethane → HCID 178451182, compound

Participants

Reaction Conditions

Reaction Steps

A 4-L flask fitted with a condenser, temperature probe and mechanical stirrer was charged with Zn metal (180.0 g, 2.76 mol, 30-100 mesh) and THF (1.25 L). While stirring 1,2-dibromoethane (4.74 mL, 0.06 mol) was added via syringe [alternatively, TMS Cl (0.1 eq.) at room temperature for one hour may be substituted]. After inert gas purge (3N2/vacuum cycles) the suspension of zinc in THF was heated to reflux (65° C.) and maintained at this temperature for 1 hour. The mixture was cooled to 50° C. before charging tert-butyl bromoacetate (488 g, 369 mL, 2.5 mol) via 50 mL syringe and syringe pump (delivery set to 4.1 mL/min) over 1.5 hours. Reaction temperature of 50°+/−50° C. was maintained throughout the addition. The reaction mixture was allowed to stir at 50° C. for one hour after the addition was complete. Subsequently, the mixture was allowed to cool to 25° C. and the precipitated product allowed to settle. The THF mother liquor is decanted into a 2-L round bottom flask using a coarse fritted filter stick and partial vacuum transfer (20 mm Hg). This removed about 65% of the THF from the mixture. 1-Methyl-2-pyrrolidinone (NMP, 800 mL) was added and agitation resumed for 5 minutes. The reaction mixture can be filtered to remove any remaining zinc. Analysis indicated a titer of desired Reformatski reagent of 1.57 M with a molar yield of 94%. Alternatively, the solid reagent can be isolated by filtration from the original reaction mixture. The cake was washed with THF until a white solid was obtained and dried under N2 to obtain the desired product as a mono THF solvate that may be stored at −20° C. (desicated) for extended periods. Typical recoveries are 85-90%.

Provenance & Evidence