A mixture of 3-(4-chlorophenoxy)-2,2-dimethylcyclopropanecarboxylic acid (0.95 g, 3.95 mmol), thionyl chloride (0.342 ml, 4.74 mmol) and DMF (several drops) in 50 ml benzene is stirred at RT for 2 days. The solvent and excess thionyl chloride are evaporated under reduced pressure. The resulting acid chloride is dissolved in 50 ml benzene, and 3-benzylpyrrolylmethyl alcohol (3.95 mmol) and 0.482 g 4-dimethtylaminopyridine (3.95 mmol) are added. The mixture is left at 25° for 18 hours and then heated under reflux for 2 hours. The mixture is then poured into water and extracted with ether. The organic phase is washed with dilute HCl, sat. NaHCO3, water and brine, dried and concentrated under vacuum. The crude product is purified by preparative TLC developing with 20% ethyl acetate/hexane to yield 3-benzylpyrrolylmethyl 3-(4-chlorophenoxy)-2,2-dimethylcyclopropanecarboxylate (A; R is hydrogen, X=X' is methyl, W is oxygen, R1 is 4-chlorophenyl).
