Double Bingel reactions

One of the most convenient of these tether-directed functionalization strategies exploits the macrocyclization of C60 with bismalonate derivatives in a double Bingel reaction.156,571 With the exception of the cis-1 bisaddition product, all possible bisaddition patterns have been obtained by this macrocyclization reaction (Figure 13). As a general... 

Possibly the simplest and most versatile method for the preparation of covalent bis-adducts of C(,o with high regio- and diastereoselectivity is the macrocyclization between C(,o and bismalonate derivatives in a double Bingel reaction [7,8,26,27], In theory, each macrocyclic regio-isomer could form as a mixture of diastereomers, depending on how the EtOCO residues at the two methano bridge C-atoms are oriented with respect to each other (in-in, in-out,... 

Dendrimers 5-8 were obtained by taking advantage of the versatile regiose-lective reaction developed in the group of Diederich [24], which led to macro-cyclic bis-adducts of Cgg by a cyclization reaction at the C sphere with bis-mal-onate derivatives in a double Bingel cyclopropanation [25]. Reaction of the dendritic malonates with Cgg, I2, and l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in toluene at room temperature afforded the corresponding cyclization products 5-8 (Fig. 2). The relative position of the two cyclopropane rings in 5-8 on the Cgo core was determined based on the molecular symmetry deduced from the and NMR spectra (Cs) as well as on their UV/Vis spectra. It is well estabhshed... 

One modification of the Bingel reaction involves DBU as a base. Initial experiments showed that exposure of CgQpjg to DBU leads to a complete loss of fluorine [71]. Fortunately this defluorination does not take place in the presence of diethyl bromomalonate. Reaction of CgQpjg with DBU and diethylbromomalonate in toluene at room temperature yields three products and unreacted CgQpjg [67, 71]. The three products are the result of mono-, bis- and tris-substitution their relative yield depends on how fast the base is added. The reaction does not - as in the usual Bingel reaction - proceed via a nucleophilic addition reaction to one double bond but as a nucleophilic substitution with a Sj.j2 -mechanism. The bromomalonate anion attacks a double bond in 5-position to one of the least sterically hindered fluorine atoms, which leads to the loss of this fluorine. The bromine atom is not replaced (Scheme 9.6). 

In 1997, a [2]catenane bearing Cgo was synthesized through Stoddart s methodology,exploiting n-n interactions between aromatic moieties. " The double Bingel addition of a [34]crown-10 bismalonate to Cgo was followed by a ring-closed reaction, where the electron-deficient cyclobis-(paraquat-p-phenylene) (CBPQT +) macrocycle recognizes the electron-rich hydroquinone template. 

Photoinduced ET was studied in fullerene bisadducts synthesized throngh a Bingel reaction bearing different kinds of macrocycles in a parachute-like shape architecture. The double addition to Cgo imposes geometrical restrictions that set the macrocycle and the fullerene moieties in spatial proximity and affects the ET as well as the CR processes. 

Besides the 1,3-dipolar cycloaddition of azomethine ylides to C60, the Bingel cycloprop anation reaction is widely used for regioselective functionalization of fullerenes. In principle, this versatile modification involves the generation of carbon nucleophiles from a-halo esters and their subsequent addition to C60 [19]. The addition takes place exclusively on double bonds between two six-membered rings of the fullerene skeleton, yielding methanofullerenes. As shown in Scheme 2, addition of diethylbromomalonate to C60, in the presence of an auxiliary base... 

The Bingel-Hirsch Reaction One of the most valuable preparative methods applicable to fullerenes is the Bingel-Hirsch reaction. This is, in detail, the nucleophilic attack of a bromomalonate on the double bond of a fuUerene in the course of which a cyclopropane ring is generated. The reaction exclusively yields the meth-anofullerene with a bridged (6,6)-bond. It has first been described by C. Bingel in 1993, and A. Hirsch subsequently optimized the conditions, so today it is one of the best controllable reactions of fullerenes and can be performed with a multitude of reagents and substrates. 

It goes without saying that the Bingel-Hirsch reaction also takes place with larger fullerenes, but contrasting C o. there are different double bonds, and so several regioisomers can arise. For the addition of diethyl malonate to C70 only the... 

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