the novel compounds of this invention are represented by the following structural formula : ## spc1 ## as employed in the instant description , the term &# 34 ; halo &# 34 ; or &# 34 ; halogen &# 34 ; is defined as including the halogen atoms fluorine , chlorine , bromine or iodine . also included within the instant invention are the non - toxic pharmaceutically acceptable salts of the above compounds . the novel compounds of this invention are useful as antiparasitic and anthelmintic agents . they are preferably employed in the treatment of fascioliasis in sheep and cattle and when so employed are combined with non - toxic carriers for either oral or parenteral use . the compositions in their various forms may contain from 0 . 01 to 95 % of the active compounds and are administered to the animal infected with liver fluke at dosage levels of from 1 to 300 mg ./ kg . of animal body weight , preferably from 5 to 100 mg ./ kg . of body weight . the particular amount of active ingredient in a composition will depend upon the particular form of composition , whether it is a premix , finished medicated feed product , solid or liquid unit dosage form , parenteral unit dosage form and the like , and also the particular type of animal being treated , its age , weight , degree of infection and the like . these compositions and their method of use in treating liver fluke infections thus form other aspects of this invention . the preferred compounds of this invention are exemplified , but not limited by the following list : the compounds of the instant invention are prepared by processes which are best visualized in the following reaction scheme : ## spc2 ## wherein r 1 , r 2 and r 3 are as previously defined and r 4 is an alkyl group of from 1 to 5 carbon atoms . in the first step of this reaction procedure , a 3 , 4 , 5 - substituted benzenesulfonamide ( i ) is reacted with an orthoester of the formula : hc ( or 4 ) 3 wherein r 4 is as previously defined , in order to form the loweralkoxymethylene derivative ( ii ). any loweralkylorthoester may be employed , the product being dependent upon the particular ester employed . the reaction is generally run in an aprotic solvent such as chloroform , benzene , toluene , acetone , tetrahydrofuran and the like . the use of a solvent is , however , optional and the product may be obtained in equally good yields without any solvent . the reaction is run at from room temperature to the reflux temperature of the reaction medium and is complete in from 15 minutes to 6 hours . there is generally employed an excess of the orthoester over the sulfonamide although exactly one molar equivalent may be employed if desired . this intermediate product is recovered by techniques known to those skilled in this art . the product compounds are prepared from the loweralkoxymethylene compounds ( ii ) by treating the latter compound with dimethylamine in an optional aprotic solvent at from room temperature to the reflux temperature of the reaction mixture when a solvent is employed , and to 150 ° c when no solvent is employed . the reaction is generally complete in from 1 / 2 to 6 hours and the product is isolated by techniques known to those skilled in this art . one molar equivalent of dimethylamine is required for the completion of the reaction , however , generally an excess of dimethylamine , up to about 10 molar equivalents is generally employed . the following examples are typical of the procedures employed to synthesize the compounds of this invention . the examples are presented so that the invention might be more fully understood and should not be construed as being limitative of the invention . 371 mg . ( 1 mmole ) of o - ethyl - n -( 3 , 5 - dibromophenylsulfonyl ) formimino ether is dissolved in 10 ml . of toluene at 35 ° c . gaseous dimethylamine is bubbled through the solution for 5 minutes maintaining the temperature at 35 ° c . the reaction mixture is stirred overnight at room temperature whereupon some crystallization is observed . the reaction mixture is concentrated by heating in an oil bath at 170 ° c . upon cooling to room temperature , the reaction mixture solidifies and is treated with ethyl acetate and filtered . the solid material is dried in vacuo at 50 ° c . affording 250 mg . of n , n - dimethyl - n &# 39 ;-( 3 , 5 - dibromophenylsulfonyl ) formamidine , melting point 157 ° to 158 ° c . recrystallization from dimethylsulfoxide / water gives pure n , n - dimethyl - n &# 39 ;-( 3 , 5 - dibromophenylsulfonyl ) formamidine , melting point 160 ° to 162 ° c . following the procedure of example 1 employing o - methyl - n ( 3 , 5 - ditrifluoromethylphenylsulfonyl ) formimino ether or o - butyl - n ( 3 - chloro - 5 - trifluoromethyphenylsulfonyl ) formimino ether in place of o - ethyl - n -( 3 , 5 - dibromophenylsulfonyl ) formimino ether there is obtained n , n - dimethyl - n &# 39 ;-( 3 , 5 - ditrifluoromethylphenylsulfonyl ) formamidine and n , n - dimethyl - n &# 39 ;-( 3 - chloro - 5 - trifluoromethylphenylsulfonyl ) formamidine , respectively . a solution of 364 mg . ( 1 mmole ) of o - ethyl - n -( 3 - iodo - 5 - cyanophenylsulfonyl ) formimino ether in 10 ml . of toluene at 35 ° c . is treated with diemthylamine gas until the solution is saturated . a precipitate forms and the mixture is stirred for one half hour at 35 ° c . and filtered . the solid material is washed with toluene and ether and dried affording 281 mg . ( 77 %) of n , n - dimethyl - n &# 39 ;-( 3 - cyano - 5 - iodophenylsulfonyl ) formamidine , melting point to 186 ° to 187 ° c . following the procedure of example 2 , employing o - butyl - n -( 3 - bromo - 5 - cyanophenylsulfonyl ) formimino ether , o - ethyl - n -( 3 - cyano - 5 - trifluoromethylphenylsulfonyl ) formimino ether or o - ethyl - n -( 4 - amino - 3 - bromo - 5 - cyanophenylsulfonyl ) formimino ether in place of o - ethyl - n -( 3 - iodo - 5 - cyanophenylsulfonyl ) formimino ether there is obtained n , n - dimethyl - n &# 39 ;-( 3 - bromo - 5 - cyanophenylsulfonyl ) formamidine , n , n - dimethyl - n &# 39 ;-( 3 - cyano - 5 - trifluoromethylphenylsulfonyl ) formamidine , and n , n - dimethyl - n &# 39 ;-( 4 - amino - 3 - bromo - 5 - cyanophenylsulfonyl ) formamidine , respectively . the starting materials for the above reactions are prepared in the following manner : 315 mg . ( 1 mmole ) of 3 , 5 - dibromobenzenesulfonamide and 1 . 0 ml . of triethylorthoformate ( 3 . 75 mmoles ) are combined and heated in an oil bath at 130 ° c . for 30 minutes . a clear solution is formed which stops bubbling after 20 minutes . the reaction mixture is cooled whereupon it solidifies completely . the solid material is washed with ethanol , centrifuged , washed again with ethanol and dried in vacuo at 50 ° c . recovering white crystals , melting point 137 ° to 139 ° c . 360 mg . of o - ethyl - n ( 3 , 5 - dibromophenylsulfonyl ) formimino ether is recovered . 3 . 08 g . ( 10 mmoles ) of 3 - iodo - 5 - cyanobenzenesulfonamide and 10 ml . of triethylorthoformate are combined and heated in an oil bath at 130 ° c . with stirring . after 15 minutes a clear solution is formed and the reaction mixture starts to bubble which continues for 30 minutes . the reaction mixture is cooled to room temperature and allowed to stand for 1 hour . the reaction mixture is washed with ethanol , filtered , and washed again with ethanol affording a solid material melting at 138 ° to 140 ° c . 3 . 45 g . of a beige solid is recovered . 293 mg . ( 1 mmole ) of 3 , 5 - ditrifluoromethylbenzenesulfonamide and 1 . 0 ml . of trimethylorthoformate are combined and heated in an oil bath at 130 ° c . for 30 minutes . a clear solution is formed which bubbles for 20 minutes after reaching the reaction temperature . the reaction mixture is cooled whereupon it solidifies completely . the solid material is washed with methanol , centrifuged , washed again with methanol and dried in vacuo at 50 ° c . recovering white crystals of o - methyl - n ( 3 , 5 - ditrifluoromethylphenylsulfonyl ) formimino ether . 2 . 61 g . ( 10 mmoles ) of 3 - bromo - 5 - cyanobenzenesulfonamide and 10 ml . of tributylorthoformate are combined and heated in an oil bath at 130 ° c . with stirring . after 15 minutes a clear solution is formed and the reaction mixture starts to bubble which continues for 30 minutes . the reaction mixture is cooled to room temperature and allowed to stand for 1 hour . the reaction mixture is filtered , and washed with butanol affording crystalline o - butyl - n -( 3 - bromo - 5 - cyanophenylsulfonyl ) formimimino ether . 2 . 81 g . ( 10 mmoles ) of 3 - bromo - 5 - nitrobenzenesulfonamide and 10 ml . of triethylorthoformate are combined and heated in an oil bath at 130 ° c . with stirring . after 15 minutes a clear solution is formed and the reaction mixture starts to bubble which continues for 30 minutes . the reaction mixture is cooled to room temperature and allowed to stand for 1 hour . it is filtered , and washed with ethanol affording crystalline o - ethyl - n -( 3 - bromo - 5 - nitrophenylsulfonyl ) formimino ether .