Organoiron complexes in organic synthesis. Part 21. Methods for controlling the regioselectivity of nucleophile addition to tricarbonyl(cyclohexadienylium)iron complexes

Abstract

A study of the regioselectivity of enolate nucleophile addition to tricarbonyl(dienylium)iron complexes with structure (1) is reported. It has been found that better selectivity for the 1-substituted dienylium terminus is achieved using 4-isopropoxy-substituents than with 4-methoxy-substituents. The nature of the enolate countercation is also found to affect significantly the regioselectivity of its addition, and these results are discussed in terms of the factors which are likely to control the reaction.