Patent GB-711811-A (GB)
Title: Improvements in or relating to 2-imino-4-thiazolines or acid salts thereof and method of preparation
IPC: C07D277/42
Filed: 1951-10-30
Abstract: 2 - Imino - 4 - thiazolines (and their salts) substituted in the 3-position are prepared by heating an anhydrous mixture of an enolisable a -thiocyano-carbonyl compound and a primary amine or salt thereof; water is split out to give a 1-(substituted amino)-2-thiocyano-ethylene which on further heating ring-closes to the imino-thiazoline.  The invention also includes the compounds 2-imino-3-aryl-thiazolines and their derivatives substituted in the 4- and/or 5-positions by alkyl or aryl.  The water produced during the reaction may be removed azeotropically by the use of a suitable diluent such as a mixture of benzene and butanol; the excess diluent is finally removed and the product recovered, after liberation from its salt if necessary.  In the examples the following substituted 2-imino-4-thiazolines are prepared: 3 - phenyl - 4 : 5 - dimethyl, 3 - phenyl - 4 - ethyl, 3 : 4 : 5 - trimethyl, 3 - ethyl - 4 : 5 - dimethyl, 3 - (31 - carboxy - 41 - hydroxyphenyl) - 4 : 5 - dimethyl, 3 - cyclohexyl - 4 : 5 - dimethyl, 3 - (b  - hydroxyethyl) - 4 : 5 - dimethyl, 3 - (b  - chloroethyl) - 4 : 5 - dimethyl, 3 - (o - hydroxyphenyl) - 4 : 5 - dimethyl, 3 - phenyl, 3 - cyclohexyl, 3 - ethyl, 3 - (b  - carbomethoxy - ethyl) - 4 : 5 - dimethyl, 3 - n - butyl - 5 - methyl, 3 : 5 - di - isopropyl, 3 : 5 - diphenyl, 3 - methyl - 5 - phenyl, 3 - n - butyl - 5 - n - propyl, 3 : 5 - dibenzyl - 4 - methyl, 3 - ethyl - 4 - n - butyl - 5 - methyl, 3 : 5 - dimethyl - 4 - phenyl, 3 - phenyl - 4 - b  - naphthyl - 5 - methyl, 3 : 5 - diethyl - 4 - n - butyl, 3 - n - propyl - 4 - (b  - phenethyl) - 5 - ethyl, 3 - benzyl - 4 - allyl - 5 - ethyl, 3 : 5 - diallyl - 4 - methyl, 3 - (a  - furyl) - 4 : 5 - dimethyl, 3 - (p - nitrophenyl) - 4 : 5 - dimethyl, 3 - (g  - methoxypropyl) - 4 : 5 - dimethyl, 3 - (o - mercapto-phenyl)-4 : 5-dimethyl and 3-(o-sulphophenyl)-4 : 5-dimethyl.  A list of further reactants is given, giving compounds where the 3-substituent is alkyl, alkenyl, cycloalkyl, aryl, aralkyl or heterocyclic, optionally carrying carboxylic, hydroxy, alkoxy, thio, chlorine, bromine, iodine, nitro and sulphonic acid substituents, and the 4- and 5-substituents are alkyl, aryl, aralkyl or cycloalkyl, optionally carrying chlorine, bromine, alkoxy, thio and nitro substituents; the 4- and 5-substituents may form a closed carbocyclic ring and bis-compounds result from the use of a diamine or a dithiocyano-diketone.  Further reactions are described involving the use of 2-imino-3-phenyl-4 : 5 - dimethyl - 4 - thiazoline: (1) it is isomerised with acid to 2-anilino-4 : 5-dimethylthiazole; (2) it is treated with dinitrochlorobenzene to give 2-(21 : 41-dinitrophenylimino)-3-phenyl - 4 : 5 - dimethyl - 4 - thiazoline; (3) treatment with sodium nitrite and acetic acid converts it to 2-(N-nitrosoimino)-3-phenyl-4 : 5-dimethyl-4-thiazoline; and (4) it is benzoylated to yield 2 - (benzoylimino) - 3 - phenyl - 4 : 5 - dimethyl-4-thiazoline. Details are also given of the reaction of aniline with 3-thiocyanobutanone to produce 2-anilino-4 : 5-dimethylthiazole.  Thiocyano-aldehydes and thiocyano-ketones are made from the corresponding halogen compounds and sodium thiocyanate. Thus butanone is chlorinated and then treated with sodium thiocyanate to give a mixture of 1- and 3-thiocyano-butanones.ALSO:Compounds of the formula <FORM:0711811/V/1> where R, R2 and R3 are organic radicals (or R1 and R2 may be hydrogen), are used as accelerators and activators in the vulcanization of rubber.  Particularly useful are those in which R1 and R2 are hydrogen or alkyl, R3 is alkyl or aryl and the total number of carbon atoms in the R groups is at least 3. Examples show the vulcanization of the following mixtures:-(1) Butadienestyrene copolymer, rosin soap, carbon, stearic acid, sulphur and 2 - imino - 3 - phenyl - 4 : 5 - dimethyl-4-thiazoline; (2) rubber, carbon, zinc oxide, stearic acid, phenyl-b -naphthylamine, sulphur and 2-imino-3-phenyl-4 : 5-dimethyl-4-thiazoline, with or without one of the following known accelerators:-dodecyl mercaptan, b -mercaptoproprionic acid, 3-mercapto-benzoic acid, 2-mercapto-4 : 6 : 6-trimethylthiazine and 2-mercapto-benzthiazole; (3) as in (2) using as accelerator a 2-mercaptothiazole salt of 2-imino-3-phenyl-4 : 5-dimethyl-thiazoline and 2-mercapto-4 : 5-dimethyl-thiazole.  Many other suitable thiazolines are mentioned.