Abstract
A highly enantioselective protocol has been recently described as allowing the synthesis of five-membered cyclic imines harnessing the selective generation of a β-Csp3-centered radical of acyl heterocyclic derivatives and its subsequent interaction with diverse NH-ketimines. The overall transformation represents a novel cascade process strategy crafted by individual well-known steps; however, the construction of the new C-C bond highlights a crucial knot from a mechanistically perspective. We believe that the full understanding of this enigmatic step may enrich the current literature and expand latent future ideas. Therefore, a detailed mechanistic study of the protocol has been conducted. Here, we provide theoretical insight into the mechanism using quantum chemistry calculations. Two possible pathways have been investigated: (a) imine reduction followed by radical–radical coupling and (b) radical addition followed by product reduction. In addition, investigations to unveil the origin behind the enantioselectivity of the 1-pyrroline derivatives have been conducted as well.
Highlights
It is unarguable that radical-based transformations are currently powerful synthetic tools for enabling unconventional bond constructions and disconnections [1,2,3,4,5,6]
A comparison between the energetic profiles of the addition to both possible options is provided in the uration that helps in delocalizing the unpaired electron
Electronic excitation energies have been computed within the Time-Dependent Density Functional Theory (TD-DFT) [32,33]
Summary
It is unarguable that radical-based transformations are currently powerful synthetic tools for enabling unconventional bond constructions and disconnections [1,2,3,4,5,6]. Deep investigations have been performed for the plausible involvement of photoredox catalysis when seeking to design molecules appreciated in the pharmaceutical area [7,8,9,10,11] The latter has resulted in a wide library of otherwise unachievable routes for molecular building; in particular, imines have proven to be reliable redox-active scaffolds in several transformations for crafting nitrogen-bearing compounds [12]. Catalysts 2021, 11, 922 other; several factors may operate to determine the fate of the mechanism as several factors may operate to determine the fate of the mechanism as it is it is properly indicated in most of the reports that summon these principles. Properly indicated in most of the reports that summon these principles
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