Quantum mechanical investigation on acceleration of electrocyclic reactions through transition metal catalysis

• First mechanistic studies on transition metal catalyzed electrocyclization.
• Oxidative addition and reductive elimination steps have been observed.
• Ligands, oxidation state and coordination number of metal show profound effect.
• Lowest activation energy of 5.63 kcal mol−1 was observed for [Nb(CHD)]+3.

Acceleration of the electrocyclization of 1,3,5-hexatriene to 1,3-cyclohexadiene through early transition metal catalysis is investigated through quantum mechanical methods. The reaction proceeds in a non-pericyclic fashion involving two fundamental steps of catalysis (oxidative addition and reductive elimination), and the calculated acceleration effect is very large, up to 24 kcal mol−1. Electrocyclization is highly dependent on the nature, formal oxidation state and coordination number of metal. Ligands are also predicted to show tremendous effect on the activation barrier of a reaction. Lowest activation energy is observed for [Nb(CHD)]+3 (5.63 kcal mol−1) where Nb is in its highest possible oxidation state i.e. +5.

Figure optionsDownload as PowerPoint slide