Theoretical and experimental study on the stereoselectivity of Michael addition of alkoxide anion to nitro olefin

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The Michael addition of alkoxide anions to nitro olefins is studied in terms of ab initio and MNDO molecular orbital calculations. We have also done experiments using nitro olefins with the same substituents calculated here. It is proposed that the stereoselectivity of the reaction is due to the endo alkoxy effect, which is structural, and the electronic effect in nitronate anion intermediates. The effect does not exist in intermediates of conjugate addition of simple alkyl group to nitro olefines. The difference depends on whether the atom in the γ-position possesses lone pair orbitals or not. High stereoselectivity was observed in the Michael addition to nitro olefins with the bulky substituents of the α-carbon. This is due to the difficulty in rotating the alkoxy fragment about the Cα-Cβ axis