Convenient synthesis of aryl halides from arylamines via treatment of 1-aryl-3,3-dialkyltriazenes with trimethylsilyl halides

Abstract

Treatment of 1-aryl-3,3-diethyltriazenes with trimethylsilyl halides in acetonitrile at 60/sup 0/C resulted in the rapid and quantitative evolution of nitrogen and in the formation of aryl halides. 1-Aryl-3,3-diethyltriazenes were prepared by a conventional route in high yields, and trimethylsilyl iodide and bromide were produced in site by the reaction of trimethylsilyl chloride with sodium iodide or lithium bromide, respectively. The high reactivity of trimethylsilyl halides toward 1-aryl-3,3-diaklytriazenes may be explained in terms of their strong electrophilicity and the marked affinity of the trimethylsilyl group toward nitrogen. The reaction rate seemed to be markedly dependent on the nature of the free halide ion in solution; iodide ion reacted faster than bromide ion, and chloride ion was only converted to the aryl chloride after an extended reaction period. In addition, in the absence of trimethylsilyl chloride, neither iodide not bormide ion reacted with the aryldialkyltriazenes under our experimental conditions. Since the trimethylsilyl chloride with sodium iodide or lithium bromide, this method is applicable to the preparation of aromatic radiohalide compounds. For example aromatic radiohalide derivatives may be prepared from bromide (/sup 75/Br or /sup 77/Br) and iodide (/sup 123/I, /sup 125/I, or /sup 131/I) with high radiochemical purity and yields which makesmore » this synthetic method useful for the preparation of radiopharmaceuticals of medicinal interest.« less