the conversion of the acetal - amine ( iib ) to its maleate salt is accomplished by reacting it , in ethyl acetate solution , with a solution of maleic acid in ethyl acetate . the molar ratio of acetal - amine to maleic acid should be at least about 1 : 1 . in actual practice , molar ratios of acetalamine to maleic acid of from about 1 : 1 to about 1 : 1 . 5 are generally used . molar ratios of maleic acid greater than 1 . 5 per mole of acetal - amine give rise to separation of excess maleic acid along with the desired maleate salt and are , therefore , not used . a favored ratio of acetal - amine to maleic acid is 1 : 1 . 2 , since it affords satisfactory yields of high quality maleate salt . the process permits use of crude acetal - epoxide , 2 - phenyl - 4h - pyrido -[ 3 , 2 - d ]- 1 , 3 - dioxin - 6 - epoxyethane ( iia ) in the large scale overall process leading to formation of final product ( iv ). in so doing , it achieves greater economic advantage over the other processes of belgian 823 , 616 not only by eliminating the need for purifying the acetal - epoxide , but also by producing an acetal - amine of higher purity and greater yield . a variety of solvents can be used in the process of this invention for forming the maleate salt . included among operable solvents are ethyl acetate , ethyl propionate , propyl acetate , acetonitrile , acetone , methanol and ethanol . among the several solvents enumerated above , ethyl acetate is preferred since it affords the maleate salt in crystalline form of high quality and in satisfactory yield . formation of the maleate salt can be carried out over a wide temperature range ; eg ., from about 20 ° c . to the boiling point of the solvent , ethyl acetate . the favored temperature range is from about 30 ° c . to about 50 ° c . in actual practice a temperature of from about 35 ° c . to 42 ° c . is used since it permits use of homogeneous solutions , convenient volume of solvent and affords optimum yield and quality of product . the maleate salt thus produced can be used as is to produce 2 - hydroxymethyl - 3 - hydroxy - 6 -( 1 - hydroxy - 2 - t - butylaminoethyl ) pyridine . it can , if desired , be purified by dissolution in hot methanol and decoloration of the solution . removal of the methanol solvent and addition of ethyl acetate to the residue affords the pure maleate salt . the final product , 2 - hydroxymethyl - 3 - hydroxy - 6 -( 1 - hydroxy - 2 - t - butylaminoethyl ) pyridine , is generally employed as the dihydrochloride salt . transformation of the acetal - amine maleate to the dihydrochloride salt of the final product ( iv ) is readily accomplished by reacting the maleate salt with an excess of hydrogen chloride . a preferred procedure comprises adding the acetal - amine maleate to methanolic - hydrogen chloride in a molar ratio of maleate salt to hcl of from about 1 : 3 to about 1 : 6 , and desirably at about 1 : 4 , at a temperature of about 20 ° c . to 25 ° c . from about 2 - 3 liters of methanol per mole of maleate salt is used . the mixture is stirred until conversion is complete , about 2 hours , and is then concentrated ; e . g ., to approximately one - fourth its original volume , under reduced pressure , and the resulting concentrate diluted with a large volume of acetone . the dihydrochloride salt of the final product precipitates , and , after granulating at about 25 ° c ., for 0 . 5 to 1 . 0 hour , is recovered by filtration or other suitable means . in addition to maleic acid , other organic acids , such as fumaric , tartaric , citric and malic acids , can be used to purify and isolate the intermediate acetal - amine . the organic salt is then converted to the dihydrochloride salt of the final product ( iv ) in the same manner as is the maleate salt . a pressure reactor is purged with nitrogen and charged with 2 - phenyl - 4h - pyrido [ 3 , 2 - d ]- 1 , 3 - dioxin - 6 - epoxyethane ( 12 . 672 kg ., 49 . 6 moles ) and t - butylamine ( 59 . 2 kg ., 810 moles ). the reactor is then pressurized to 30 p . s . i . with nitrogen and heated and stirred at 80 ° c . for 28 hours . the reactor is then cooled to 20 ° c . and allowed to stand overnight . the reaction mixture is concentrated under reduced pressure to about 25 liters volume . benzene ( 95 liters ) is added to the oily concentrate and the resulting solution concentrated to about 25 - 30 liters volume under reduced pressure . a second charge of benzene ( 95 liters ) is added to the concentrate and the solution concentrated to about 25 liters volume . to the residue of acetal - amine , a thick slurry , ethyl acetate ( 45 liters ) is added and the mixture heated to 40 ° c . to dissolve the slurry . a solution of maleic acid ( 7 . 0 kg ., 60 moles ) in ethyl acetate ( 135 liters ) at 40 ° c . is added to the acetal - amine solution to precipitate the crystalline maleate salt . the mixture is stirred for one hour and is then cooled to 25 ° c . after stirring at 25 ° c . for 1 hour , the crystalline maleate salt is recovered by filtration , washed with ethyl acetate ( 60 liters ) and dried . yield 13 . 3 kg ., 60 . 0 %. m . p . 192 °- 195 ° c . ( dec .). it is purified by dissolution in methanol ( 208 liters ) at 50 ° c . and decolorization of the solution with activated charcoal . concentration of the decolorized solution , including 38 liters of methanol washed solution from washing the charcoal filter cake , to small volume followed by addition of ethyl acetate ( 200 liters ) precipitates the purified salt . it is filtered , washed with ethyl acetate and dried . m . p . 195 °- 196 . 5 ° c . yield 12 . 3 kg . analysis : ca . c &# 39 ; d for c 23 h 28 n 2 o 7 : c , 62 . 15 ; h , 6 . 35 ; n , 6 . 30 %, found : c , 62 . 21 ; h , 6 . 32 ; n , 6 . 38 % a pressure reactor is purged with nitrogen and charged with 2 - phenyl - 4h - pyrido [ 3 , 2 - d ]- 1 , 3 - dioxin - 6 - epoxyethane ( 13 . 53 kg ., 53 moles ) and t - butylamine ( 62 . 7 kg ., 859 moles ). the reactor is then pressurized to 30 p . s . i . with nitrogen and heated and stirred at 80 ° c . for 28 hours . the reactor is then cooled to 10 ° c . and allowed to stand overnight . the reaction mixture is concentrated under reduced pressure to about 38 liters volume . benzene ( 102 liters ) is added to the oily concentrate and the resulting solution concentrated to about 30 - 35 liters volume under reduced pressure . a second charge of benzene ( 102 liters ) is added to the concentrate and the solution concentrated to about 25 liters volume . to the residue of acetal - amine , a thick slurry , ethyl acetate ( 57 liters ) is added and the mixture heated to 40 ° c . to dissolve the slurry . a solution of maleic acid ( 7 . 424 kg ., 64 moles ) in ethyl acetate ( 144 liters ) at 40 ° c . is added to the acetal - amine solution to precipitate the crystalline maleate salt . the mixture is stirred for 1 hour and is then cooled to 25 ° c . after stirring at 25 ° c for 1 hour , the crystalline maleate salt is recovered by filtration , washed with ethyl acetate ( 60 liters ) and dried . yield = 16 . 1 kg ., 68 . 3 %. m . p . 176 °- 180 ° c . ( dec .). to a solution of methanol ( 11 . 3 l .) -- hydrogen chloride gas ( 620 g ., 17 moles ) at 20 ° c . is added , with stirring , 2 - phenyl - 6 -( 1 - hydroxy - 2 - t - butylaminoethyl )- 4 - h - pyrido -[ 3 , 2 - d ]- 1 , 3 - dioxin maleate ( 1880 g ., 4 . 24 moles ) over a five minute period . the resulting solution is then stirred for 2 hours at 20 °- 25 ° c . and is then concentrated under reduced pressure to a volume of about 3 liters . acetone ( 16 liters ) is added to the concentrate and the resulting precipitate granulated at 25 ° c . for a half - hour . the white crystalline solid is separated by filtration and washed with acetone ( 4 liters ). yield = quantitative . m . p . 183 °- 187 ° c . ( dec .). a solution of methanolic - hydrogen chloride ( 27 . 4 g . hcl gas in 400 ml .) and 2 - phenyl - 6 -( 1 - hydroxy - 2 - t - butylaminoethyl )- 4h - pyrido [ 3 , 2 - d ]- 1 , 3 - dioxin ( 112 . 3 g .) is stirred at 25 ° c . for 3 . 5 hours . acetone ( 2 . 4 liters ) is added to the reaction mixture over a period of 15 minutes . a dark colored oil forms . the mixture is concentrated under reduced pressure to give a slurry . acetone ( 1 . 5 liters ) is added and the slurry granulated for a half - hour at room temperature . the tan solid , plus some darker brown lumps , is filtered and dried ( 72 . 8 g .). the solid is dissolved in methanol ( 300 ml . ), treated with activated charcoal and filtered . the charcoal is washed with methanol ( 50 ml .) and the combined filtrate and wash diluted with acetone ( 1 . 5 liters ). the resulting hazy solution is stirred for one hour and the off - white precipitate produced is filtered , washed with acetone and dried ( 59 g ., 55 . 1 %). m . p . 176 °- 182 ° ( dec . ).