REACTIVITY OF DIENETRICARBONYLIRON COMPOUNDS IN FRIEDEL-CRAFTS ACYLATION

Relative reactivities for substituted dienetricarbonyliron compouds toward the methyloxocarbonium tetrachloroaluminate ion pair in dichloromethane have been determined by a competition method. Substituent effects are generally small. However, substituted carbons are not attacked themselves, and acyl groups are strongly deactivating. Some diene complexes which give low yields of acylation product react rapidly with the electrophile nevertheless. These data require that formation of the transition state for electrophilic attack causes small decreases in electron density at the diene carbons. Our data along with data from the literature seem most consistent with rate determining electrophilic attack at carbon. © 1979.