SHORT COMMUNICATIONS Suzuki et al. [1] were the first to report in 1991 on cycloaddition of diphenyldiazomethane to fullerene C 60 . Since that time, numerous publications have appeared on reactions of fullerene with mono-and disubstituted diazomethanes, cyclic diazo compounds, and diazoacetates [2,3]. All these reactions may be divided into two groups, the first of which includes addition of diazoalkanes to C 60 with formation of mixtures of [5,6]-fulleroids and [6,6]-methanofullerenes, while the second is represented by thermal reactions of fullerene C 60 with diazo compounds generated in situ from the corresponding p-tolylsulfonylhydrazone lithium salts; the latter reactions lead to selective formation of [5,6]-open adducts. Disadvantages of the above procedures are low selectivity, experimental difficulties related to extreme instability of substituted diazoalkanes, and low yield of the target cycloadducts.We previously reported [4] on selective cycloaddition of diazomethane (generated in situ) to C 60 in the presence of palladium complexes. In continuation of these studies, the present communication reports on cycloaddition of alkyl(aryl)-substituted diazoalkanes to C 60 in the presence of palladium complexes, which was examined with a view to reveal the effect of diazoalkane structure on the reaction direction and develop efficient procedures for the synthesis of substituted [5,6]-fulleroids.We found that three-component catalyst prepared from Pd(acac) 2 , PPh 3 , and Et 3 Al showed the highest catalytic activity and selectivity in reactions of C 60 with diazoacetates [5,6]. Preliminary experiments showed that palladium complexes were also more efficient than copper or rhodium compounds in reactions with diazoalkanes. The reaction of C 60 with diazoethane (molar ratio 1.5 : 1) generated in situ by oxidation of acetaldehyde hydrazone with Ag 2 O was carried out in o-dichlorobenzene at 20°C (reaction time 20 min) in the presence of 20 mol % of Pd(acac) 2 -PPh 3 -Et 3 Al (1 : 2 : 4) gave [5,6]-open adduct Ia in ~70% yield with high selectivity. Increase of the reaction time to 1 h did not result in appreciable improvement of the yield of Ia (~75%). Following an analogous procedure, fullerene C 60 was brought into reactions with 2-diazopropane, phenyldiazomethane, and 1-diazo-1-phenylethane, which led to the formation of 55-70% of [5,6]-open adducts Ib-Id. It is seen that the yield of the adducts decreases as the size of substituents in the initial diazoalkanes increases. R = H, R′ = Me (a); R = R' = Me (b); R = H, R′ = Ph (c); R = Me, R′ = Ph (d).