Mechanism Study of Mn(I) Complex-catalyzed Imines and Alkynes Dehydrogenation Coupling Reaction

Abstract

With the development and widespread use of transition metal catalysts, C-H activation has become a hot topic in organic synthesis, especially in the construction of CC bond of organic compounds. As an important and cheap catalyst, manganese complex has shown great potential for catalyzing C-H activation both in academic and industrial applications. In this paper, the mechanism of manganese-catalyzed dehydrogenative [4＋2] annulation by C-H/N-H activation was investigated systematically with the aid of density functional theory (DFT) calculations in 1,4-dioxane solvent. In detail, we use M06-L/[SDD:6-311＋G(d,p)(SMD)]//M06-L/[LANL2DZ:6-31G(d)] to examine the Gibbs free energy, structure and other properties of possible intermediates and transition states in this catalytic cycle. By comprehensive comparison and discussion, we obtained a favorable pathway consisting of five steps: (1) catalyst initiation occurred with the assistance of bromine anion rather than imide to form active catalyst; (2) alkyne inserted into the active catalyst to generate a seven-membered manganacycle after dissociation of a carbon monoxide; (3) double bond migration happened in this seven-membered manganacycle to form a product precursor; (4) the product precursor would dissociate by β-H elimination and generated product isoquinoline and active Mn-H complex; (5) the active Mn-H complex was subsequently combined with an imine followed by dehydrogenative C-H activation to complete the whole catalytic cycle. In this context, the reason for the highly atom-economical C-H activation by direct dehydrogenation (eliminates the necessity for oxidants or additives) has been clarified by this mechanism. The present study was aimed at further understanding of Mn(I)-catalyzed dehydrogenative C-H activation, and provided more theoretical basis for future more Mn-catalyzed C-H activation.

Computational Design of Functionalized Metal–Organic Framework Nodes for Catalysis

“…Among the density functionals that have proven useful in the KS-DFT context, we single out the Minnesota functional M06-L, , which has shown a good performance in reproducing experimental trends and being able to accurately predict spin-state energetics in MOFs in good agreement with high-level methods, such as the CASPT2 method. , The M06-L functional has been validated for many applications relevant to catalysis − (including some cases very similar to the cases discussed in the next section but also including studies relevant to the broader applicability for transition metal catalysis and barrier heights) and MOFs. , …”