Improved process for the preparation of 1-substituted amino-1-substituted thio-2-nitro alkenes

A process is disclosed for the manufacture of 1-substituted amino-1-substituted thio-2- nitro alkenes of the general formula: (R1 NH) (R2S)C=CR3(NO2) wherein R1, R2, R3 may be the same or different and may consist of hydrogen, alkyl, aryl, arylalkyl groups or combinations thereof. These alkenes are prepared by reacting a primary amine with a compound of sulfur in the presence of a primary catalyst to obtain a carbonimidodithioic acid salt which is converted to a corresponding ester which is thereafter reacted with a nitro compound in the presence of a secondary catalyst. 1-methylamino-1-methylthio-2-nitroethene is an important intermediate in the synthesis of Rantitidine and Nizatidine which are antiulcer drugs and associated gastrointestinal disorders.