Bingel

Klahn, B. and Bingel, W. A. [19 77] The Convergence of the Rayleigh-Ritz Method in Quantum Chemistry , Theoretica Chimica Acta, 44, p. 9. 

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... 

Schantz L.D., Laber-Laird K., Bingel S. and Swindle M. (1996). Pigs apphed anatomy of the gastrointestinal tract , in Jensen S.L., Gregersen H., Moody F. and Shokouh-Amiri M.H. Essentials of Experimental Surgery Gastroenterology, Harwood Academic Publishers NY, 2611-2619. 

SCHEME 22. Synthesis of Cgo malonates by Bingel s procedure, followed by glycodendronization. ... 

SCHEME 23. Synthesis of a bismannoside-C6o adduct using the Bingel-Hirsch procedure.231... 

Figure 15.8 The Bingel reaction for the modification of fullerenes involves the in situ formation of a reactive halogen species in the presence of the strong base DBU. The cyclopropanation product can be used to create many bioconjugates.

Figure 15.9 The reaction of the amine-blocked derivative of 3-hydroxypropylamine with ethylmalonyl chloride gives an ethylmalonate-protected-amine compound, which can be used in the Bingel reaction to create an amine group on a fullerene surface. Reaction with Cfl in the presence of I2 and DBU gives the cyclopropanation product that can be deprotected with TFA to yield the free amine.

Figure 15.10 Fullerene-PCBM derivatives can be prepared using reactive diazo intermediates, which yield a cyclopropanation product similar to the Bingel reaction derivatives.

Following the discovery of a bulk fullerene preparation process in 1990, the covalent chemistry of these carbon allotropes has developed at a phenomenal pace. Frontier orbital (LUMO) and tether-directed functionalization concepts have been successfully applied to the regio- and stereoselective preparation of multiple covalent adducts of C60. These have found increasing applications in the construction of functional supramol-ecules. More recently, the sequence of Bingel reaction - retro-Bingel reaction has provided an elegant access to isomerically pure higher fullerenes and, in particular, to pure carbon enantiomers. 

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... 

Scheme 7. Optical resolution of ( )-C76 by the Bingel/ retro-Bingel reaction sequence.

Figure 14. Formation of fully differentiated nexa.-Bingel adducts by a "3+3" addition scheme.

The two most commonly used derivatization methods for exohedral functionalization are the nucleophilic cyclopropanation with malonates (Bingel, 1993) and the formation of fulleropyrrolidines (Maggini et al., 1993). Both of these protocols have been used extensively to produce water-soluble fullerenes for biomedical applications. Other stable water-soluble fullerene adducts have also been reported (Hirsch and Brettreich, 2005). Sections 3.2.2-3.2.5 will give a short overview on the state-of-the-art of water-soluble fullerene derivatives and outline some general trends for designing such molecular structures. 

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