8. o-Chlorophenyl cyclopentyl ketone.
To the thus obtained Grignard soln there’s added 48 g o-chlorobenzonitrile and the mixture is stirred for 3 days at RT. It is then poured into a mixture of ice/NH4Cl, with addition of some conc. aq. NH3 and left at ambient temp until all ice melts. The ketone partially floats, partially goes to the bottom. It’s extracted with benzene (Use 100 mL x2 times). The yields fluctuate, but rarely drop below 55%.
Step 2: alpha-bromo (o-chlorophenyl)-cyclopentyl ketone.
To 21.0 g of the above ketone is added 10.0 g of bromine in 80 ml of carbon tetrachloride dropwise at 0 °C. After all the Br2 has been added, an orange suspension forms. This is washed with a dilute aqueous solution of sodium bisulfite (~65 mL x2 of 10% solution) and evaporated to give 1-bromocyclopentyl-(o-chlorophenyl)-ketone, bp 111-114 °C (0.1 mm Hg). Yield is ~66%. This bromoketone is unstable and must be used immediately. Also, attempts to distill it at 0.1 mm Hg lead to some decomposition, so it should be used without further purification.
To the thus obtained Grignard soln there’s added 48 g o-chlorobenzonitrile and the mixture is stirred for 3 days at RT. It is then poured into a mixture of ice/NH4Cl, with addition of some conc. aq. NH3 and left at ambient temp until all ice melts. The ketone partially floats, partially goes to the bottom. It’s extracted with benzene (Use 100 mL x2 times). The yields fluctuate, but rarely drop below 55%.
Step 2: alpha-bromo (o-chlorophenyl)-cyclopentyl ketone.
To 21.0 g of the above ketone is added 10.0 g of bromine in 80 ml of carbon tetrachloride dropwise at 0 °C. After all the Br2 has been added, an orange suspension forms. This is washed with a dilute aqueous solution of sodium bisulfite (~65 mL x2 of 10% solution) and evaporated to give 1-bromocyclopentyl-(o-chlorophenyl)-ketone, bp 111-114 °C (0.1 mm Hg). Yield is ~66%. This bromoketone is unstable and must be used immediately. Also, attempts to distill it at 0.1 mm Hg lead to some decomposition, so it should be used without further purification.
