Modification of Regioselectivity in Cycloadditions to C70 under Microwave Irradiation
The Journal of Organic Chemistry2000Vol. 65(8), pp. 2499–2507
Citations Over TimeTop 10% of 2000 papers
Fernando Langa, Pilar de la Cruz, António de la Hoz, Eva Espı́ldora, Fernando P. Cossío, Begoña Lecea
Abstract
The regioselectivity of the cycloaddition of N-methylazomethine ylide to C70 can be modified by using microwave irradiation as the source of energy. Under microwave irradiation and by choosing the appropriate solvent and irradiation power, the 5-6 isomer is the major product, a situation that is in contrast to conventional heating where the 1-2 isomer predominates. Moreover, isomer 7-21, which represents 13% of monoadducts under classical heating, is not formed under microwave irradiation and with ODCB as solvent. Theoretical calculations predict an asynchronous mechanism and suggest that the modification of the regiochemical outcome is related to the relative energies and hardnesses of the transition structures involved.
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