Early main group metal catalysis: How important is the metal?

Article abstract of DOI:10.1002/anie.201408814

Organocalcium compounds have been reported as efficient catalysts for various alkene transformations. In contrast to transition metal catalysis, the alkenes are not activated by metal-alkene orbital interactions. Instead it is proposed that alkene activation proceeds through an electrostatic interaction with a Lewis acidic Ca2+. The role of the metal was evaluated by a study using the metal-free catalysts: [Ph₂N^-Me₄N⁺] and [Ph₃C^-][Me₄N^- ]. These "naked" amides and carbanions can act as catalysts in the conversion of activated double bonds (C=O and C=N) in the hydroamination of Ar-N=C=O and R-N=C=N=R (R=alkyl) by Ph₂NH. For the intramolecular hydroamination of unactivated C=C bonds in H₂C=CHCH₂CPh₂CH₂NH₂ the presence of a metal cation is crucial. A new type of hybrid catalyst consisting of a strong organic Schwesinger base and a simple metal salt can act as catalyst for the intramolecular alkene hydroamination. The influence of the cation in catalysis is further evaluated by a DFT study.