Benzodioxole was monochloromethylated directly by aqueous formaldehyde and hydrogen chloride gas in CCl4 in the presence of quaternary ammonium salts: C16H33-（CH3）3NX（X=Br,Cl）, C12H25（CH3）3NCl,C12H25（CH3）2（C6H5CH2）NCl and （C4H9）4NBr. With hexadecyltrimethylammonium bromide at temperature 6065 ℃ and for 15 hours of reaction, 1,3-benzodioxole was converted to piperonyl chloride with conversion more than 98% and selectivity up to 97%. The method has advantages of high selectivity, high conversion, negligible by-products and easy workup of the main product.
