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The S,Ar substitutions of a number of 5-X-substituted indoles (1 a-f ), 5-X-substituted 2methylindoles (1 g-j) and N-methylindole (1 k) by 4,6-dinitrobenzofuroxan (DNBF) have been kinetically studied in 70-30 (v/v) H,O-Me,SO, 50-50 (v/v) H,O-Me2S0, methanol and acetonitrile. The absence of a significant dependence of the rates of reactions on the hydrogen or deuterium labelling at C-3 of the indole ring indicates that electrophilic attack (kyNBF) by DNBF at this position is the rate-limiting step of the substitutions. However, the kYNBf rate constants are strongly sensitive to the solvent polarity, the observed reactivity sequence being 70-30 H,O-Me,SO > 50-50 H,O-Me,SO > methanol > acetonitrile. This trend is consistent with a highly 10 7

The syntheses of several functionalised aryl cyanate esters bearing reactive allyl groups are presented. The monomers were purified (to c. 98%) using preparative HPLC and a range of techniques, including heteronuclear nuclear magnetic resonance (NMR) spectroscopy, was employed in their characterisation. A model functionalised aryl cyanate ester was doped with a variety of additives and the resulting thermal behaviour examined using dynamic differential scanning calorimetry (DSC). Furthermore, the postulated co‐reaction of the model functionalised cyanate ester with bis‐maleimides was investigated using heteronuclear NMR and dynamic mechanical techniques.