Unexpected radical substitution of the dichlorine-containing iron(II) clathrochelate with 1,4-dioxane derivatives: Novel approach to functionalization of its macrobicyclic framework

Free-radical Reaction of the Iron(II) Dichloroclathrochelate with Tetrahydrofurane Radical Derivatives: Synthesis and Structure of the Monotetrahydrofuryl-Containing Cage Complex

“…These δ H and δ C values are characteristic of a CH moiety attached to a strong electron-withdrawing group (atom), and this is the С 2 H fragment of the ribbed tetrahydrofuryl substituent at the macrobicyclic framework. This conclusion is supported by analogous spectral pattern observed earlier for the 1,4-dioxanyl-substituted iron(II) clathrochelate [1] and the 1 H -13 C HMBC spectrum used for the study of the longrange 1 H -…”

“…This reaction mainly afforded the mono-and bis-1,4-dioxan-2-yl-substituted iron(II) macrobicyclic complexes. [1] This paper describes a similar reaction of the tetrahydrofuryl radical, as well as the structure of the major monosubstituted tetrahydrofuryl-containing clathrochelate product (both in solution and in the solid state) and its spectral characteristics. Н NMR spectrum were determined by simulation of the spin system with NUMMRIT algorithm and the method of totallineshape fitting (RMS = 0.1357, R = 0.0067, SpinWorks 3.1.8., Bruker Topspin 2.1).…”

Using Minisci Reaction for Modification of the tris-Dioximate Metal Clathrochelates: Free-Radical Substitution at the Glyoximate Fragment of an Iron(II)-Encapsulating Cage Framework

“…Other main bond lengths and angles in the macrobicyclic framework and those in the rib 1,4-dioxan-2-yl substituent have usual values. [22,23] This substituent adopts 2 (where R are 1,4-dioxan-2-yl, tetrahydrofuran-2-yl or 1,3-dioxolan-2-yl substituents) reported in literature [10,11,13] and the clathrochelate under study are crystallized in this chiral space group, independently on the nature of a monofunctionalized cage molecule (i.e. is it chiral or not).…”

“…Mechanistically, the first stage of the above reaction is identical to that of the radical substitution of chlorine atom in a dichloroclathrochelate FeBd 2 (Cl 2 Gm)(BF) 2 (where Cl 2 Gm 2-is dichloroglyoxime dianion) with 1,4-dioxan-2-yl radical, [10] whereas the destinies of their intermediate spin adducts are different. Indeed, the chlorine atom, being a good leaving group, detaches from this intermediate giving the clathrochelate product FeBd 2 (ClGm(diox))(BF) 2 (Scheme 2,ii).…”

“…[6,7] Keeping in mind a pseudoaromatic character of the highly conjugated polyazomethine cage frameworks of the tris-dioximate metal clathrochelates and their electron-deficient nature stemming from the positive charge of the encapsulated metal ion, we aimed to apply the Minisci reaction for homolytic alkylation of these macrobicyclic substrates. Homolytic ribbed functionalization of the iron(II) cage tris-dioximates has been earlier performed using free radical substitution of the reactive chlorine atom of a dichloroclathrochelate precursor with carbon-centered radicals as shown in Scheme 1(i) [8][9][10][11][12][13] and by free-radical reductive double alkylation of the methyl substituted azomethine group of the corresponding cage framework as well [14,15] (Scheme 1,ii). Here we report the homolytic radical alkylation of a monomethylglyoximate iron(II) cage complex FeBd 2 Mm(BF) 2 as a substrate under Minisci reaction conditions, as well as the detailed X-ray structural and spectral characterization of the macrobicyclic product of this reaction.…”