Trichloroacetyl chloride, condensation

A. Pyrrol-2-yl trichloromethyl ketone. In a 3-1. three-necked round-bottomed flask equipped with a sealed mechanical stirrer, a dropping funnel, and an efficient reflux condenser with a calcium chloride drying tube are placed 225 g. (1.23 moles) of trichloroacetyl chloride and 200 ml. of anhydrous ether. The solution is stirred while 77 g. (1.15 moles) of freshly distilled pyrrole in 640 ml. of anhydrous ether is added over 3 hours (Note 1). The heat of reaction causes the mixture to reflux during the addition. Following the addition, the mixture is stirred for 1 hour, and then 100 g. (0.72 mole) of potassium... 

To a 750-mL flame-dried, five-necked flask equipped with a condenser, addition funnel, stirrer, thermometer, and nitrogen inlet were added 13.0 g ethyl 3-methyl-2-butenyl sulfide (0.10 mol), 7.2 g activated zinc (0.11 mol), and 200 mL anhydrous ether. Under stirring, a solution of 11.5 mL trichloroacetyl chloride (18.5 g, 0.105 mol) in 100 mL anhydrous ether was added to the suspension over a period of 4 h. After that, an additional 3.5 g activated zinc (0.05 mol) was added to the flask, and the mixture was stirred for an additional hour. Pentane (200 mL) was added to precipitate the zinc salts, and the solution was decanted from the residue. The residue was washed twice with ether-pentane (50 mL), and the combined solutions was washed successively with water, a cold solution of 10% NaHCOs, and brine and then dried over MgS04. Upon removal of solvent under vacuum, 17.2 g of crude ethyl thioester of 2,2-dichloro-3,3-dimethyl-4-pentenoic acid was obtained which was further purified by vacuum distillation to give 9.1 g product, in a yield of 38% (should be >38%), b.p. 66°C 0.25 mmHg. 

A dry, two-necked, round-bottom flask is equipped with a 250-mL pressure-equalizing addition funnel and a condenser topped with a gas inlet. The system is Bushed with N2. The flask is charged with zinc (origin specified above, 11.77g, 0.180 mol), lead dichloride (0.25 g, 0.9 mmol), anhydrous ether (450 mL), and 1-methyl-l-cyclohexene (from Aldrich, 11.8 mL, 9.62 g, 0.100 mol). The addition funnel is filled with a solution of freshly distilled trichloroacetyl chloride (16.7 mL, 27.2 g, 0.150 mol) in 150 mL of anhydrous ether. The flask is then partially submerged in an ultrasonic bath (Kerry Ultrasonic Pulsatron 250,47 kHz), in the place that maximizes agitation. 

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