Computational Study of the Ene/Rearrangement Reaction between (F3C)2B═NMe2, 1, and Acetonitrile: Reactant-Catalyzed Mechanism of the Ketenimine-Nitrile-Like Rearrangement.

The reaction between (F3C)2B═NMe2, 1, and acetonitrile at low temperature in pentane yields a bora-acetonitrile rather than the expected coordination complex. This appears to arise from the two undergoing an ene reaction followed by a rearrangement analogous to a ketenimine-nitrile rearrangement. Computational studies indicate that mechanistic steps suggested for the latter require energies too large for the reaction to take place under the experimental conditions. Instead, a mechanism in which the ene reaction product is attacked by a second molecule of 1, followed by hydrogen transfer and decomposition, exhibits barriers lower than that for the ene reaction. The mechanism implies that the fragment of 1 in the observed product is not the one that underwent the ene reaction. The ene reaction barrier is rate-determining, and it is low enough to conform to the experimental conditions.