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A series of asymmetrical spirohomo- and methanofullerenes were synthesized for the first time in reactions of selective cycloaddition of adamantane diazo compounds to C60 fullerene in the presence of the catalyst Pd(PPh3)2Cl2. Adamantane diazoalkanes were obtained in situ in the oxidation reactions of adamantane hydrazones with manganese oxide MnO2. It has been established that the presence of adamantyl on the methylene bridge (in the case of symmetry of the spirocyclic fragment), methyl and ethyl substituents, or no substituents (in the case of asymmetry of the spirocyclic fragment) leads to the formation of exclusively [5,6]-open isomers (homofullerenes); when the hydrocarbon radical (butyl and nonyl radical) is extended on the methylene bridge of the asymmetric spirocyclic fragment, only [6,6]-closed isomers (methanofullerenes) are formed. All homofullerenes obtained in this work do not isomerize into the corresponding methanofullerenes under thermal conditions (180°C, 100 hours). Homofullerenes containing an adamantyl radical (in the case of symmetry of the spirocyclic fragment) or not containing substituents (in the case of asymmetry of the spirocyclic fragment) on the methylene bridge do not isomerize into the corresponding methanofullerenes under the influence of ultrasound (room temperature, 5 hours). For the first time, sonochemical isomerization of spirohomofullerenes containing electron-donating methyl and ethyl groups on the methylene bridge into methanofullerenes was carried out under mild conditions (1.5 hours, toluene, room temperature, air). Atmospheric oxygen does not affect the isomerization reaction. The presence of CCl4, which forms CCl3● radicals during sonolysis, suppresses isomerization reactions, which indicates the participation of radical particles in the rearrangement process. A probable mechanism for the structural rearrangement of homofullerenes into methanofullerenes under the action of ultrasound is proposed.
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