Bingel-Hirsch reaction

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. 

Figure 2.56 From a preparative point of view, the Bingel-Hirsch reaction counts among the most valuable transformations because it tolerates a wide variety of...

Figure 2.56 collects some exemplary reactions of Ceo with different bromoma-lonates and other applicable keto compounds. This collection shows that there is virtually no Umit to the choice of side chains, which renders the Bingel-Hirsch reaction an attractive and flexible starting point for the synthesis of fuUerene-containing materials. For example, the base-mediated conversion of a malonate and Cao into the respective methanofullerene can also be achieved. With the semiester of malonic acid instead of a malonate, the monosubstituted methanofullerene is obtained because the primary product is instantaneously decarboxylated (Figure 2.56). P-Ketoesters may also be reacted under Bingel-Hirsch conditions to give methanofuUerenes.

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... 

The Bingel-Hirsch reaction is an important tool in fullerene functionalization. It yields cyclopropanated fullerenes by means of deprotonated bromomalonates. 

Figure 3.73 The Bingel-Hirsch reaction on carbon nanotubes and examples of subsequent reactions on the respective products.

In 2007 two independent contributions made by Cordova and co-workers [14] and by W. Wang and co-workers [15] reported a simple and highly stereoselective cyclopropanation via the reaction of enals (15) and 2-bromomalonates (18). Catalyst VII allowed, based on a Michael addition and subsequent intramolecular a-alkylation (i.e., a Bingel-Hirsch reaction) of the enamine intermediate, the production of the cyclopropane motif 17 (Scheme 10.9, B). 

This method complements the widely used Prato and Bingel-Hirsch reactions. The derived, highly functionalized cyclopentenone and cyclopentenamine fullerene compounds are suitable for further functionalization upon hydrolysis and may serve well in the synthesis of new Cgo derivatives possessing uncommon and interesting properties... 

SCHEME 2.1 Examples of C q established functionalization methods, (a) [1 + 2] cycloaddition, (b) [2 + 2] photochemical cycloaddition, (c) [3 + 2] cycloaddition of azomethine ylides, (d) [4 + 2] Diels-Alder cycloaddition, and (e) Bingel-Hirsch reaction. 

Furthermore, substituted methanofullerenes can be produced by addition/elimina-tion reactions (Bingel, 1993 Hirsch et al., 1994 Anderson et al., 1994a), but they are not within the scope of this book. 

The Bingel reaction has also been used to prepare bis-adducts of C o and the relative distribution of the regioisomers that are obtained has been analyzed in detail by Hirsch and his coworkers, and partially rationalized using statistical and theoretical arguments [6]. All of the... 

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