Background: The aryldiazonium salts (ArN2
+X-) are useful intermediates in organic synthesis.
Although well stablished, the generation of ArN2
+X- from anilines usually requires the use of
corrosive and hazardous strong acids (HCl, H2SO4 or HBF4). The use of weak acids from a renewable
source for diazotization reaction is infrequent and not well investigated.
Methods: The goal of this work is to verify if vinegar, an easily available solution of acetic acid can
act both as a acid source and as a solvent to promote the diazotation reaction. The reactivity of the aryldiazonium
acetates was evaluated by addition of KI (Sandemeyer reaction) or furan (Gomberg-
Results: Using 1 equivalent of KI and 1.2 equivalents of NaNO2, substituted iodoarenes were obtained
with poor to good yields. We observed in this two-step iodination protocol, the anilines that contained
electron withdrawing groups performed better than those with electron donating groups. For the arylation
reaction, higher amounts of furan and NaNO2 were required. In this case, the corresponding substituted
arylfurans were also obtained with poor to good yields. Similar to the diazotization-iodination
reaction, this arylation of furan with anilines containing electron withdrawing groups (Br, NO2) performed
better than the same reaction with anilines containing electron donating groups.
Conclusion: Substituted iodoarenes and arylfurans can be synthesized directly from anilines in vinegar,
without the use of metals, additives or catalysts. The dual role of vinegar (acting as a solvent and
acid source) combined with the green aspects (low cost, low toxicity, renewable) and the simplicity
makes this method attractive.