the process of this invention is illustrated by the following reaction sequence : ## str1 ## in which r is lower alkyl of 1 - 4 carbons , preferably methyl , and r 1 is chloro or fluoro . one skilled in the art will recognize that substituents on the respective phenyl rings of the two starting materials will not , to the best of our knowledge , influence the chemical reaction of the hemimercaptal of formula 1 with the phenethylamine of formula 2 . for example , the methoxy substituents may be replaced by hydrogen , higher alkoxy groups , ethylenedioxy or methylenedioxy , the latter two on the methoxy substituted phenethylamine . the 2 - halo substituent may also be replaced by hydrogen , trifluoromethyl , lower alkyl , lower alkylthio or similar substituents as known to the benzazepine art . the chemical process of this invention comprises the reaction of the hemimercaptal of formula 1 and the phenethylamine of formula 2 in an organic solvent , which is inert to the reactants and in which the reactants are substantially soluble , until the coupling is complete . an excess of either starting material may be optionally present but usually stoichiometric quantities are used . in fact , an excess of the primary amine may give better yields of isolated thioether intermediate of formula 3 . suitable solvents are selected from the preferred lower alcohols such as methanol , ethanol , propanol or isopropanol , ethers such as tetrahydrofuran , dimethylsulfoxide , dimethylformamide , dimethyl acetamide , aromatics such as benzene , toluene or xylene , esters such as ethyl acetate , halohydrocarbons such as chloroform , carbon tetrachloride , ethylene dichloride , methylene chloride or mixtures thereof . methanol or aqueous mixtures of methanol are preferred . the reaction is conveniently run at room temperature until complete , usually from 1 - 12 hours . if the phenethylamine is used in the form of an acid addition salt , such as the hydrochloride or hydrobromide , an equivalent quantity of an acid binding agent , such as an alkali metal lower alkoxide , hydroxide or carbonate , is added to generate the base in situ . higher temperatures , up to the reflux temperature , of the reaction mixture , are optionally used , such as when the solubility of a starting material is a problem . when methanol is used as solvent , the intermediate of formula 3 , for example , n -[ 2 -( 2 - chloro - 3 , 4 - dimethoxyphenyl ) ethyl ]- 2 - keto - 2 -( p - methoxyphenyl )- 1 - methyl - thioethylamine , is easily separated from the reaction mixture by precipitation . the thioether intermediates of formula 3 are new compounds and are an important aspect of this invention . optionally , the operator may isolate the α - thio intermediate of formula 3 or he may continue with the reactions of sequence a without isolation . the α - thio compound is treated with a reducing agent capable of converting a keto group to a hydroxy group . unexpectedly , this reaction simultaneously removes the α - alkylthio group in the form of a lower alkyl mercaptan by - product . reducing agents include the traditional ones which are used in the art to convert a keto group to a hydroxy . examples are metal - acid , such as zinc dust - acetic acid or iron and acetic acid , zinc - sodium hydroxide in ethanol or a meerwein reduction . splitting a ring methoxy substituent during the reduction is not unacceptable but care should be taken to use a reducing agent which will not attack halo substituents . more suitable reduction means , especially when a halo is present on one of the phenyl rings of compound 3 , are the borohydride reducing agents . most useful of these are the alkali metal borohydrides , such as sodium or potassium borohydride . others include ; the alkali metal trialkylborohydrides , such as lithium or potassium trisiamylborohydrides and lithium or potassium tri - sec .- butylborohydrides , the alkali metal trialkoxyborohydrides such as sodium or potassium triisopropoxyborohydrides . also useful are the corresponding hydrides such as lithium aluminum hydride , sodium aluminum hydride , diisobutyl aluminum hydride , sodium diethylaluminum hydride or sodium bis -( 2 - methoxyethoxy ) aluminum hydride . organic solvents commonly used in hydride or borohydride reactions will be recognized as applicable to this reaction , for example , lower alcohol , tetrahydrofuran , glyme , diglyme , dimethylformamide , sulfolane . most usefully , the reaction is carried out using at least two equivalents of sodium borohydride in methanol until the reaction is complete , maintaining the temperature below 20 ° initially , then , allowing it to obtain room temperature . the overall yield of the one - pot , two step reaction runs from 50 - 80 % of product which is isolated by standard chemical procedures . if the overall two step reaction of sequence a is run without isolation of the thioether , the solvent must be selected to accommodate the reducing agent . the secondary amines of formula 4 are converted into biologically active end products as described in example 2 of u . s . pat . no . 4 , 197 , 297 . for example , the secondary amine is treated with concentrated sulfuric acid - trifluoroacetic acid or methanesulfonic acid - methylene chloride to form the benzazepine ring . protective groups such as alkyl ethers , if present , are , then , split using boron tribromide - methylene chloride or 48 % hydrobromic acid to obtain the desired end product . the following examples are designed to illustrate the practice of this invention . all temperatures are centigrade . other variations of these examples will be obvious to those skilled in the art . a 22 l flask was charged with 526 . 6 g ( 2 . 48 m ) of p - methoxyphenylglyoxal methyl hemimercaptal and 626 . 3 g ( 2 . 48 m ) of 2 - chloro - 3 , 4 - dimethoxyphenethylamine hydrochloride followed by 7 . 4 l of methanol and 535 . 8 g ( 2 . 48 m ) of 25 % sodium methoxide / methanol . the mixture was stirred at room temperature for 3 hours , then , chilled to 0 °. sodium borohydride ( 200 g , 5 . 26 m ) was added at a rate which maintained reaction temperature below 20 °. the mixture was stirred for 8 hours while allowing the reaction mixture to warm to room temperature . the methanol was stripped off in vacuo at less than 50 °. about 2 . 5 l of 10 % hydrochloric acid was added to give a ph of 1 . methylene chloride ( 2 . 25 l ) was added . the mother organic extract combined with two follow - up liter extracts was taken to half volume at which time 5 . 6 l of ethyl acetate was added . after stirring until the desired product had separated completely , 505 . 19 g ( 50 . 8 %) of n -[ 2 - hydroxy - 2 -( p - methoxyphenyl ) ethyl ]- 2 -( 2 - chloro - 3 , 4 - dimethoxyphenyl ) ethylamine was recovered by filtration , washing with 1 l of ethyl acetate and oven drying . this material was identical with that described in the prior art by nmr . a . a mixture of 3 . 6 g ( 0 . 017 m ) of p - methoxyphenylglyoxal methyl hemimercaptal , 4 . 61 g ( 0 . 0213 m ) of 2 - chloro - 3 , 4 - dimethoxyphenethylamine and 70 ml of methanol was stirred at room temperature for 3 hours . the precipitated solid was separated by filtration , washed with propanol and air - dried to give 5 . 53 g ( 79 %) of n -[ 2 -( 2 - chloro - 3 , 4 - dimethoxyphenyl ) ethyl ]- 2 - keto - 2 -( p - methoxyphenyl )- 1 - methylthioethylamine , m . p . 75 °- 78 °. anal . calcd . for c 20 h 24 nso 4 cl : c , 58 . 60 ; h , 5 . 90 ; n , 3 . 42 ; s , 7 . 82 ; cl , 8 . 65 . found : c , 58 . 47 ; h , 5 . 98 ; n , 3 . 43 ; s , 8 . 01 ; cl , 9 . 00 . b . a mixture of 3 . 40 g ( 16 mm ) of p - methoxyphenylglyoxal methyl hemimercaptal , 3 . 46 ( 16 mm ) of 2 - chloro - 3 , 4 - dimethoxyphenethylamine and 90 ml of methanol was stirred at room temperature for 72 hours . methanol was stripped off to give an oil . methanol ( 20 ml ) was added with no crystallization upon chilling . two ml of cyclohexane was added . with chilling , 1 . 86 g of the thioether separated . a portion of the thioether ( 0 . 3 g , 0 . 73 mm ) in methanol was reacted with 0 . 06 g ( 1 . 46 mm ) of sodium borohydride . after 1 hour , all the reactants had gone into solution . high pressure , liquid chromatographic reverse phase analysis ( hplc ), ( over silica with 60 : 40 methanol / water buffered with acetic acid and octanesulfonic acid as mobile phase ) demonstrated almost quantitative conversion to n -[ 2 - hydroxy - 2 -( p - methoxyphenyl ) ethyl ]- 2 -( 2 - chloro - 3 , 4 - dimethoxyphenyl ) ethylamine . the methylthio compound ( 500 mg ) dissolved in an acid solution ( hplc acid phase from above ) at ph 3 was allowed to stand for 24 hours , at which time , there was demonstrated disappearance of the methylthio absorption at 10 min . and appearance of peaks corresponding to hemimercaptal ( 34 %) and primary amine ( 9 %). a mixture of 3 . 9 g ( 2 mm ) of 2 - fluoro - 3 , 4 - dimethoxyphenethylamine , 4 . 4 g ( 2 mm ) of p - methoxyglyoxal methyl hemimercaptal and 10 ml of ethanol is reacted at 35 ° for two hours . brief concentration and cooling gives n -[ 2 -( 2 - fluoro - 3 , 4 - dimethoxyphenyl )- ethyl ]- 2 - keto - 2 -( p - methoxyphenyl )- 1 - methylthioethylamine . the methylthio intermediate ( 1 . 5 g ) is reacted with two equivalents of sodium borohydride in tetrahydrofuran at 40 ° to give n -( 2 - hydroxy - 2 -( p - methoxyphenyl ) ethyl ]- 2 -( 2 - fluoro - 3 , 4 - dimethoxyphenyl ) ethylamine .