Synthesis of (η6-arene)(η5-cyclopentadienyl) iron (II) complexes with heteroatom and carbonyl substituents Part II, Amino substituents

A variety of methods have been used in the synthesis of amino-substituted (η6-arene)(η5-cyclopentadienyl) iron(II) complexes. Conventional thermal ligand exchange of 2-fluoroaniline with ferrocene in the presence of Devarda’s alloy gave an Ullmann coupling product, 2,2′ diaminobiphenyl complex, whereas omitting metal powder gave the 2-fluorobenzene complex. Double SNAr substitution of the 1,2-dichlorobenzene complex by dimethylamine is reported. Microwave-assisted SNAr reactions have led to the development of a one-pot synthesis of N-arylaminoacids. Acetylation of amino-complexes is described and the product anilide complexes used in SNAr displacements to form aminoanilide analogues. Hexamethyldisilazane was found to be an efficient aminating agent in the presence of alcohols or phenols in DMSO, leading to the synthesis of the (η6-1,2-diaminobenzene)(η5-Cp) iron(II) complex, the first (ArFeCp)+ species reported containing two primary amino groups.

Graphical abstractSynthesis of arene-cyclopentadienyl iron (II) complexes having amino and amido substituents using microwave-mediated reactions and conventional methods, including rapid arylation of aminoacids.(i)Ferrocene, ALCl3, graphite, Devarda’s alloy, microwave (X = F, Y = NH2)(ii)[EtO2CCH2NH3][Cl], Et3N, graphite, DMF, microwave (X = H, Y = F)(iii)KOtBu, microwave(iv)Ac2O (X = F,Cl), Y = NH2(v)[NH4][OH](vi)(Me3Si)2NH, PhOH, DMSO (X = F, Y = NH2)Figure optionsDownload full-size imageDownload as PowerPoint slide