It was established that the direction of interaction of O,O-dialkyldithiophosphoric acids (1) with N-alkyl-2-halogenoaldimines (2-3) on the whole depends on halogen atom nature. Reaction of acids (1) with N-alkyl-2-chloroaldimines (2) was studied by the dynamic 1H, 13C and 31P NMR spectroscopy in intervals of temperature -60°-25°C. It was found that it involves two stages. At the first stage the protonation of the imine group and the formation of intermediate immonium salt [N-alkyl-2-chloro-2-methylpropaneimmonium O,O-dialkyldithiophosphate (4)] takes place. At the second stage the chlorine atom is replaced with O,O-dialkyldithiophosphate group. The final reaction products are the N-alkyl-2-O,O-dialkyldithiophosphato-2-methylpropaneimmonium chlorides (5). It is supposed that salt (4) transforms into product (5) via the formation of substituted azoallyl dication by heterolytic dissociation of tertiary carbon-chlorine bond. Dithiophosphato-substituted immonium salts contain the corresponding pharmacophoric groups and therefore they are potential biological active substances. Reaction of the N-alkyl-2-bromoaldimines (3) with O,O-dialkyldithiophosphoric acids has absolutely different synthetic result: phosphoryldisulfide and bromine nonsubstituted immonium salt (N-alkyl-2-methylpropaneimmonium bromide) (6) are formed as the final reaction products. It begins already at -90°C and N-alkyl-2-bromo-2-methylpropaneimmonium O,O-dialkyldithiophosphates (7) are firstly formed which at temperatures higher -80°C transformed gradually into final salts (5). In conclusion, new reaction was discovered to reduce the bromine-substituted immonium salts by means of O,O-dialkyldithiophosphoric acid.
The work was supported by the Russian Foundation for Basic Research and Tatarstan Republic government (grant no. 13-03-7098) and by the Ministry of Education and Science of Russian Federation (within the basic part of task # 2014/56).