Regioselective nitrile addition to hindered tricarbonylcyclohexadienyliumiron complexes and spirolactone formation

Article abstract of DOI:10.1021/om00025a042

By using a large excess of trimethylsilyl cyanide and a short reaction time, trimethyl isocyanide in sufficient amount is generated and added regioselectively at the C-1 terminus of the tricarbonyl cyclohexadienylium species 1, irrespective of steric hindrance and its α-proton acidity. Formation of the aromatic and trienyl complex is suppressed. Upon saponification or hydrolysis, addition product 2c is converted into the synthetically useful spirolactone 6. For the reaction mechanism, formation of phosphorus pentafluoride, trimethylsilyl fluoride, and free cyanide during the reaction between hexafluorophosphate anion and trimethylsilyl cyanide is suggested.