Jump to main content
Jump to site search

Issue 35, 2018
Previous Article Next Article

Computational mechanistic elucidation of the rare earth metal-mediated cycloamidination of aminoalkenes with nitriles

Author affiliations

Abstract

A detailed computational probe of the rare earth metal-mediated intramolecular amidination of aminoalkenes with nitriles by an archetypical [Y{N(SiMe3)2}3] precatalyst is presented. The mechanistic picture derived from smooth energy profiles, acquired by employing a reliable computational protocol applied to a realistic catalyst model, conforms to available experimental data that includes a significant primary KIE. Sequential Y–N silylamide aminolysis transforms the precatalyst into a multitude of silylamide/amide compounds, of which the bis-amine coordinated [Y{N(SiMe3)2}(NRR′)2] is the most abundant, capable of promoting cycloamidination. Nitrile insertion is irreversible and readily furnishes the κ2-N-amidinate yttrium intermediate, which readily rearranges into more stable isomers featuring κ2-N,Δ and κ1-N(imine) amidinate ligations. Its bis-amine adduct likely represents the catalyst resting state. The alkenylamidine becomes accessible through kinetically affordable Y–N amidinate bond protonolysis, which can best be viewed as a kinetically mobile equilibrium that favours the amidinate. The generation of 2-imidazoline product via N–C bond forming amidinate cyclisation favours a stepwise σ-insertive cyclisation/Y–C alkyl aminolysis sequence over an otherwise kinetically prohibitive proton-triggered concerted N–C/C–H bond forming process. The operative σ-insertive pathway entails reversible olefin 1,2-insertion followed by turnover-limiting Y–C alkyl aminolysis at the short-lived 4-imidazolylalkyl intermediate. The DFT estimated primary KIE associated with aminolysis is gratifyingly close to the observed value, thereby supporting the derived mechanistic view.

Graphical abstract: Computational mechanistic elucidation of the rare earth metal-mediated cycloamidination of aminoalkenes with nitriles

Back to tab navigation

Supplementary files

Publication details

The article was received on 21 Jun 2018, accepted on 06 Aug 2018 and first published on 14 Aug 2018


Article type: Paper
DOI: 10.1039/C8DT02537A
Citation: Dalton Trans., 2018,47, 12264-12272
  •   Request permissions

    Computational mechanistic elucidation of the rare earth metal-mediated cycloamidination of aminoalkenes with nitriles

    S. Tobisch, Dalton Trans., 2018, 47, 12264
    DOI: 10.1039/C8DT02537A

Search articles by author

Spotlight

Advertisements