PROCESS FOR OBTAINING SUBSTITUTED 3,4-DIMETHOXY-BETA-PHENETYLAMINES

1392674 Dopamine derivatives ELI LILLY & CO 9 April 1973 [12 April 1972] 16835/73 Heading C2C The invention comprises dopamine derivatives of Formula (I) in which R and R 1 are H or CH 3 , at least one being H; R 2 and R 3 are H or OH at least one being OH; n is 1 or 2; and when n is 1 and R 2 and R 3 are both OH, then either R or R 1 is CH 3 ; and the pharmaceutically acceptable addition salts thereof with mineral acids. They may be prepared by reacting a compound of Formula (II) in which R 1 is hydrogen, R 2 1 and R 3 1 are H or CH 3 O- at least one being methoxy, n is 1 or 2; and when n is 1 and R21 and R 3 1 are both CH 3 O, then R or R 1 is CH 3 ; with hydrobromic acid and optionally converting to pharmaceutically acceptable salts. The methyl ethers used as starting materials may be prepared as follows: (a) the compounds of Formula II in which R is methyl and R 1 is hydrogen are prepared by the reductive alkylation of a methoxylated phenylethylamine or a methoxylated phenyl propyl amine with 3,4-dimethoxyphenylacetone; (b) the compounds in which R is methyl and R 1 is hydrogen may also be prepared by reacting 3,4- dimethoxyphenylacetone with a methoxylated phenethylamine or a methoxylated phenylpropylamine in the presence of p-toluene sulphonic acid to form the imine which is then reduced to the secondary amine; (c) the compounds in which R is hydrogen and R 1 is methyl may be prepared by the reductive alkylation of 3,4-dimethoxyphenylethylamine with the desired mono- or dimethoxylated phenyl butane-3-one (n=2) or the mono- or di-methoxylated phenylacetone (n = 1); (d) the compounds in which R is hydrogen and R 1 is methyl may also be prepared by the condensation of 3,4-dimethoxyphenylacetic acid with a methoxylated 1 -phenyl-3-aminobutane (n=2) or with a methoxylated 1-phenyl-2- aminopropane (n =1) to form as an intermediate the methoxylated amide which is reduced under nitrogen with borane to provide the secondary amine; and (e) the compounds in which R and R 1 are both hydrogen may be prepared by the alkylation of 3,4-dimethoxyphenylethylamine with a methoxylated phenyl-n-propyl bromide (n=2) or with a methoxylated phenyethyl bromide (n= 1). The products of Formula (I) are used in pharmaceutical agents.