Reaction of (η4-cycloheptatriene)Fe(CO)3 with haloketenes: structure and reactivity of the cycloadducts

Reaction of (η4-cycloheptatriene)Fe(CO)3 (1) with dichloroketene (2) generated by treatment of trichloroacetyl chloride with activated zinc, gave a [2+2] cycloadduct 3 along with a small amount of σ,π-allyl complex 4 and ε-lactone-type 1:2 adduct 5. However, 1 reacted with 2 generated by treatment of dichloroacetylchloride with triethylamine to give a 1:2 ester adduct 13 as a main product. Complex 1 also reacted with chloroketene, which was generated by treatment of dichloroacetyl chloride with activated zinc, to give a [2+2] cycloadduct 23 in a better yield in comparison with the case of 2. The cycloadduct 3 was converted to several interesting compounds.