Sequential Tether-Directed Synthesis of New [3 : 2 : 1] Hexakis-Adducts of C60 with a Mixed Octahedral Addition Pattern

Regioselective Synthesis of Hamilton-Receptor-Fullerene Oligo-Adducts for the Supramolecular Binding of Cyanuric Derivatives

A new concept for the regioselective synthesis of Hamilton-receptor and cyanurate-functionalized oligo adducts of the fullerene C60 was developed. Based on an in-situ deprotection and click-post-functionalization approach with novel azido precursors, the corresponding fullerene hexakis-adducts with octahedral addition patterns and up to twelve Hamilton-receptor/cyanurate moieties surrounding the fullerene sphere were synthesized. The versatility of this approach was further demonstrated by the synthesis of Hamilton-receptor/cyanurate functionalized fullerene mono-adducts, which are not accessible by direct cyclopropanation. Several fullerene target compounds were purified by simple washing procedures of the solid crude reaction mixture without the need for chromatography. The resulting fullerene mono- and hexakis-adducts were fully characterized and their supramolecular properties were investigated by NMR-spectroscopy and isothermal titration calorimetry (ITC).

Isocyanide-Induced Annulation Leading to Cyclopento-, Methano-, and Cyclopentano-[60]Fullerene Derivatives

The three-component annulation reactions of C₆₀, alkyl isocyanide, and dimethyl acetylenedicarboxylate (DMAD) or unsymmetric alkynes are investigated to afford cyclopent-2-en-1-imino- and ketenimine methano-[60]fullerene derivatives, which, upon hydration in the presence of acid, yield the corresponding fullerene amides. Dimethyl 2,3-pentadienedioate, the allene counterpart of DMAD, and ethyl buta-2,3-dienoate undergo four-component annulation with C₆₀, alkyl isocyanide, and water under similar conditions to yield cyclopentano-[60]fullerene derivatives with similar amide groups.

Sequential Tether-Directed Synthesis of New [3 : 2 : 1] Hexakis-Adducts of C60 with a Mixed Octahedral Addition Pattern

A new concept for the regioselective synthesis of [3 : 2 : 1] hexakis-adducts of fullerene C₆₀ was developed. Based on sequential tether-directed remote functionalizations, chiral [3 : 2] pentakis-adducts with an incomplete octahedral addition pattern were synthesized via stepwise cyclopropanation of C₆₀ with suitable macrocyclic tri- and bifunctional cyclomalonate tethers. The four resulting stereoisomers were isolated using chiral HPLC. The corresponding pairs of enantiomers show mirror image behavior in their CD-spectra. The pentakis-adducts served as suitable building blocks for the spatially controlled synthesis of mixed hexakis-adducts. Implementation of functional group-bearing monomalonates afforded octahedral [3 : 2 : 1] hexakis-adducts suitable for the construction of larger molecular and supramolecular fullerene architectures in excellent yield.