Samarium(III) carbenoid as a competing reactive species in samarium-promoted cyclopropanation reactions

The trivalent samarium carbenoid I2SmCH2I-promoted cyclopropanation reactions with ethylene have been investigated and are predicted to be highly reactive, similarly to the divalent samarium. carbenoid ISmCH2I. The methylene transfer and carbometalation pathways were explored and compared with and without coordination of THF solvent molecules to the carbenoid. The methylene transfer was found to be favored, with the barrier to reaction going from 12.9 to 9.2 kcal/mol compared to barriers of 15.4-17.5 kcal/mol for the carbometalation pathway upon the addition of one THF molecule.