Bromoacetonitrile → 7-Cyano-5-oxoheptanoic acid

To a solution of potassium hexamethyldisilazide (66 ml, 60 mmol) in dry tetrahydrofuran (140 ml) at -70° is added slowly 5-oxohexanoic acid (36 ml, 30 mmol). The resulting yellow suspension is stirred at -70° for 1 h and bromoacetonitrile (2.2 ml, 32 mmol) is added slowly. The reaction mixture is stirred at -70° for 1 h and then at room temperature for 0.5 h. The reaction is quenched by addition of 1N aqueous hydrochloric acid (100 ml). The aqueous layer is extracted twice with ether. Combined organic layer is dried, filtered and evaporated to obtain a dark oil which is purified by silica gel chromatography using 9:1 ether/hexane with 1% acetic acid as eluent to give 7-cyano-5-oxoheptanoic acid as an oil.