Dipolarophiles 60 fullerene

Compound 318 used as dipolarophile with ylide 315 (Ar = 2,4,6-Me3C6H2) gives spiro compound 319 (Equation 46) <2001HCA3403>. The 1,3-dipolar cycloaddition of 3-oxo-2-pyrazolidinium ylide 315 (Ar = Ph) with buckminsterfullerene Cgo yields new heterocyclic fullerene derivatives <1995TL2457>. 

Cycloaddition with nitrile oxides occur with compounds of practically any type with a C=C bond alkenes and cycloalkenes, their functional derivatives, dienes and trienes with isolated, conjugated or cumulated double bonds, some aromatic compounds, unsaturated and aromatic heterocycles, and fullerenes. The content of this subsection is classified according to the mentioned types of dipolarophiles. Problems of relative reactivities of dienophiles and dipoles, regio- and stereoselectivity of nitrile oxide cycloadditions were considered in detail by Jaeger and... 

The fullerenes, parttCulabiy Qq, have been well characterized (1-3), but few reports about their chemical reactivity appeared 4-6). It has been proposed that the relatively high electronegativity of this carbon cluster was due to its pyracylene character (2). Further, the inter-five-membered ring bonds are fulvenoid and are potent electrophilic as well as dienophilic and dipolarophilic sites 5, 7). 

Cycloadditions 1,3-dipoles readily react with the (6,6)-double bond of C o that acts as a highly reactive dipolarophile. Five-membered rings are generated on the fullerene s surface this way, and these can bear a multitude of functional groups. Suitable 1,3-dipoles include, for instance, nitrile oxide, azomethine ylides, alkylazides, diazo compounds or trimethylenemethane (Figure 2.60). 

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