1492349 Dioxo-isoquinolines, their preparation and use DR KARL THOMAE GmbH 29 July 1976 [30 July 1975 21 May 1976] 31725/76 Heading C2C Compounds of the formula  wherein A and B, which may be the same or different, each represents a C 2-4  straight chain saturated alkylene radical optionally substituted by a methyl or phenyl group, R 1 , R 2 , R 3  and R 4 , which may be the same or different each represents a hydrogen, fluorine, chlorine or bromine atom, a hydroxy, amino, nitro or acetylamino group or an alkyl, alkoxy or alkylthio group each of which may contain from 1 to 3 carbon atoms, R 5 , R 6 , R 7  and R 8  which may be the same or different, each represents a hydrogen atom or a C 1-4  alkyl group which is optionally substituted by a phenyl or methoxyphenyl group, or R 5  and R 6  and/or R 7  and R 8  together represent C 2-5  straight chain saturated alkylene radicals and R 9  represents a hydrogen atom or a C 1-6  alkyl group optionally substituted by a phenyl group, and acid addition salts thereof, may be obtained by a number of methods; (a) by reacting a compound of the formula where W represents an oxygen atom or an imino group, or a derivative thereof of the formula where X and X&lt;SP&gt;1&lt;/SP&gt;, which may be the same or different, each represents a halogen atom or a hydroxyl or alkoxy group, with a compound of formula where Y represents an amino group or a group of the formula suitably at 0-250 C. in a solvent in the presence of a base; (b) by reacting a compound of the formula where Z represents a nucleophilically exchangeable group, with a compound of formula suitably at -50 C. to 250 C. in a solvent in the presence of an acid binding agent; (c) by reacting a compound of the formula where D represents a C 1-3  straight chain saturated alkylene radical optionally substituted by a methyl or phenyl group and R 10  represents hydrogen or a methyl or phenyl group with the proviso that when D represents a methyl or phenyl substituted alkylene radical, R 10  represents hydrogen, with a compound of formula where E represents hydrogen or a group of formula in the presence of a reducing agent, e.g. hydrogen in the presence of a hydrogenation catalyst such as Pd/C at a pressure of 5 at., or a complex metal hydride, suitably at 0-100 C. in a solvent; (d) by alkylating a compound of Formula (I) wherein at least one of R 1 , R 2 , R 3  and R 4  represents a hydroxyl group and/or at least one of R 5 , R 6 , R 7 , R 8  and R 9  represents hydrogen, for example using an appropriate alkyl halide or dialkyl sulphate, suitably in a solvent at 20-200 C. in the presence of a base; (e) by methylating a compound of Formula (I) where R 9  is hydrogen, with formaldehyde/ formic acid; (f) by nitrating a compound of Formula (I) wherein at least one of R 1 -R 4  is hydrogen; (g) by reducing a compound of Formula (I) wherein at least one of R 1 -R 4  represents a nitro group, or (h) by acetylating a compound of Formula (I) wherein at least one of R 1 -R 4  represents an amino group. Physiologically compatible salts may be obtained by reacting a compound of Formula (I) with an appropriate acid. 4,4 - Dimethyl - 2 - [N - methyl - N - (2- aminomethyl) - aminoethyl] - 1,2,3,4 - tetrahydro - isoquinoline - 1,3 - dione is obtained by reacting 4,4 - dimethyl - 2 - (2 - methylaminoethyl) - 1,2,3,4 - tetrahydro - isoquinoline - 1,3- dione with formalin/NaHSO 3 , reacting the product with sodium cyanide, and reducing the resultant nitrile. 4,4 - Dimethyl - 2 - (4 - aminobutyl) - 1,2,3,4- tetrahydro-isoquinoline-1,3-dione is obtained by reducing the corresponding 2-(3-cyanopropyl)- derivative. The products possess pharmacological (antiarrhythmic) properties and may be formulated and applied in a conventional manner.