7,7-Dichlorobicyclo[3.2.0]hept-2-en-6-one

clear brown liquid

Under nitrogen protection, to a solution of dichloracetyl chloride (34 g, 0.23 mol) and cyclopentadiene(60 ml, 0.7 mol) in pentane (230 ml), heated to reflux in a three-necked flask with constant pressure funnel and condenser tube, was added dropwise via funnel triethylamine (24 g, 0.24 mol) in pentane (100 ml) with mechanical stirring during 4 hours, and a lot of white triethylamine hydrochloride was produced. After reflux for 2 hours, water (80 ml) was added to dissolve the triethylamine hydrochloride. The reaction mixture was extracted with pentane (2 × 60ml). The combined extracts were filtered and dried over anhydrous Na2SO4, and concentrated in vacuo to give brownish black oil. Fraction of reduced pressure distillation at 83~87 °C/400 Pa was collected to give 7,7-Dichlorobicyclo[3.2.0]hept-2-en-6-one (2, 33.5 g) as a colorless oil.