Metal ions and complexes in organic reactions. Part XV. Copper-catalysed substitutions of aryl halides by phthalimide ion

Abstract

Copper-catalysed nucleophilic substitutions, ArHal → ArN(CO)₂C₆H₄(and thence ArNH₂ by hydrolysis) are effective with a wide range of aromatic bromo- or iodo-derivatives; they are preferably carried out with potassium phthalimide and copper(I) iodide in refluxing dimethylacetamide. Reductive substitution. ArHal → ArH, is rarely competitive, but accompanying decarboxylation occurs in the case of halogenocarboxylic acids. Rates of halide substitution are dependent on the ratio of potassium phthalimide to copper(I) iodide. These two reagents solubilise each other and are considered to associate in cuprate complexes which react with the halides. Rates of substitution of para-(or meta-)halogeno-compounds, XC₆H₄Hal, show relatively small dependence on the polar character of X. The substitutions are however very susceptible to steric inhibition, as is evidenced by the behaviour of polycyclic halides and of compounds of the type o-XC₆H₄Hal, particularly if polar effects in the substituents X do not provide partial compensation.