Triethylamine → Ethyl 3-methyl-4-oxobutanoate

A solution of 53.18 g of 3A in 400 ml of dry methylene chloride was cooled to -78° C. Ozone was passed through the cold solution for 3.5 hours, air was passed through the solution for 10 minutes, then the solution was allowed to warm. At -50° C., 41.63 g of triethylamine was added drop-by-drop slowly. A strongly exothermic reaction occurred immediately, and the mixture was maintained at 5°-10° C. over the period of addition of the amine (30 minutes). The mixture then was stirred at room temperature for 2 hours, the solvents were evaporated under reduced pressure, and the residue was vacuum-chromatographed on silica gel, ether being used as eluent. The solution thus obtained was dried (MgSO4) and the solvent was evaporated to give ethyl 3-methyl-4-oxobutanoate (3B), as a slightly unstable pale yellow oil.