Synthese
The general procedure for the synthesis of 6-bromo-2-hexanone using 1-methylcyclopentanol as starting material was as follows: a mixture of 1-methylcyclopentanol (4.00 g, 39.94 mmol) and potassium carbonate (K2CO3, 33.11 g, 239.6 mmol) in chloroform (CHCl3, 130 mL) was stirred for 15 min at 0 °C. Subsequently, bromine (10.23 mL, 199.7 mmol) was added slowly. The reaction mixture was continued to be stirred at 0°C for 2.5 hours. Upon completion of the reaction, the mixture was slowly poured into ice-cold saturated aqueous sodium thiosulfate (Na2S2O3, 100 mL). The organic layer was separated, washed with water (2 x 100 mL), dried over magnesium sulfate (MgSO4), filtered and concentrated in vacuum. The residue was purified by silica gel column chromatography (eluent: petroleum ether/ethyl acetate, 3:1) to afford the target product 6-bromo-2-hexanone as a colorless oil (4 g) in 56% yield (98% purity, UV detection at 214 nm, no ESI signal detected). The 1H-NMR (400 MHz, CDCl3) data of the product were as follows: δ1.66-1.80 (m, 2H), 1.82-1.93 (m, 2H), 2.15 (s, 3H), 2.48 (t, J=7.3 Hz, 2H), 3.41 (t, J=6.5 Hz, 2H).
