REACTIONS OF TRIORGANOSTANNYL IONS WITH HALOARENES IN LIQUID-AMMONIA - COMPETITION BETWEEN HALOGEN-METAL EXCHANGE AND ELECTRON-TRANSFER REACTIONS

The reactions between triorganostannyl ions and haloarenes in liquid ammonia can lead to substitution and to reduction products. It was found that, depending on the structure of the tin nucleophile, the halogens involved, the structure of the haloarene, and the experimental conditions, the reactions can follow exclusively either an S(RN)1 mechanism (substitution products), or a halogen-metal exchange (HME) mechanism (dehalogenation-reduction products) and that a competition between both mechanisms (mixture of substitution and reduction products) is also possible. With triphenylstannyl ions (2) good yields of products of nucleophilic substitution (S(RN)1 mechanism) were obtained when the reactions were carried out with chloroarenes (e.g., p-chlorotoluene, p-dichlorobenzene, 1-chloronaphthalene, and 2-chloroquinoline) and with some bromoarenes (e.g., p-bromotoluene); with iodoarenes only HME reaction products were obtained. With trimethylstannyl ions (17) only chloroarenes reacted through the S(RN)1 mechanism. The relative reactivity of 2, 17, and diphenylphosphide ions toward p-anisyl radicals, obtained in competition experiments, is also reported.