Reactivity of co-ordinated ligands. Part XI. The relative reactivity of tricarbonyliron–cyclohexadienone and –cycloheptadienone

Abstract

The tricarbonyliron complexes of cyclohexa-2,4-dienone and cyclohepta-2,4-dienone undergo the Reformatskii reaction with methyl α-bromoacetate and zinc to give the expected hydroxy-esters. Both esters lose the hydroxy-group on reaction with trityl tetrafluoroborate to give dienyl salts. The salts are readily deprotonated to give neutral complexes with a substituted exocyclic double bond. Tricarbonyl(cyclohexa-2,4-dienone) iron shows no enol reactivity, but tricarbonyl(cyclohepta-2,4-dienone)iron undergoes the Mannich reaction with dimethylammoniumchloride and paraformaldehyde to give the expected α-dimethylaminomethyl derivative.