Laboratorium für Organische Chemie, ETH Zürich, Rämistrasse 101, 8092, Zürich, Switzerland.
Chemistry. 2022 Jul 6;28(38):e202200332. doi: 10.1002/chem.202200332. Epub 2022 May 27.
Au-catalyzed hydroamination proceeds well for alkynes but not alkenes. We report gas-phase binding energies of alkenes and alkynes to a cationic Au center, which indicate that differences in binding are not the origin of the disparate chemical behavior. We further report the synthesis and characterization of 2-aminoalkylgold complexes, which would be the intermediates in a hypothetical Au-catalyzed hydroamination of styrene. The reactivity of the well-characterized and isolable complexes reveals that protonation or alkylation of the 2-aminoalkylgold complexes results in amine elimination in solution, and in the gas phase, indicating that the failure of Au-catalyzed alkene hydroamination derives from a non-competitive protodeauration step. We analyze possible transition states for the protodeauration, and identify an insufficiently strong Au-proton interaction as the reason that the transition states lie too high in energy to compete.
金催化的氨氢化反应在炔烃中进行得很好，但在烯烃中却不行。我们报告了烯烃和炔烃在阳离子金中心的气相结合能，这表明结合能的差异不是它们化学行为不同的原因。我们进一步报告了 2-氨基烷基金配合物的合成和表征，它们将是假设的金催化苯乙烯氨氢化反应的中间体。这些具有良好特征和可分离的配合物的反应性表明，质子化或烷基化 2-氨基烷基金配合物会导致胺在溶液中消除，而在气相中则表明金催化的烯烃氨氢化反应的失败源于非竞争性的脱金步骤。我们分析了脱金的可能过渡态，并确定 Au-质子相互作用不够强是过渡态能量过高而无法竞争的原因。
