Nucleophilic aromatic substitution on tricarbonylchromium complexed haloarenes: synthesis of O-aryloximes and their cyclization to benzofurans

A series of O-aryloximes I have been prepd. from tricarbonylchromium-complexed haloarenes II and ketoximes under mild conditions. I underwent decomplexation in the presence of iodine and further cyclized in the presence of H2SO4 to give benzofuran derivs. E.g. II (R1 = H, X = Cl) reacted with R2CR3:NOH (R2 = R3 = Me) to give I (same R1, R2, R3). Sequential treatment of I with iodine followed by 98% H2SO4 gave benzofuran III.