Issue 27, 2015

Aluminium-catalysed intramolecular hydroamination of aminoalkenes: computational perusal of alternative pathways for aminoalkene activation

Abstract

A comprehensive computational examination of alternatively plausible mechanistic pathways for the intramolecular hydroamination (HA) of aminoalkenes utilising a recently reported novel phenylene-diamine aluminium amido compound is presented. On the one hand, a proton-assisted concerted N–C/C–H bond-forming pathway to afford the cycloamine in a single step can be invoked, and, on the other, a stepwise σ-insertive pathway that involves a relatively fast, reversible migratory olefin 1,2-insertion step linked to a less rapid, irreversible Al–C alkyl bond protonolysis. The present study, which employs a sophisticated and reliable computational methodology, supports the prevailing mechanism to be a stepwise σ-insertive pathway. The predicted effective barrier for turnover-limiting aminolysis compares favourably with reported catalytic performance data. Non-competitive kinetic demands militates against the operation of the concerted proton-assisted pathway, which describes N–C bond-forming ring closure triggered by concomitant amino proton delivery at the C[double bond, length as m-dash]C linkage evolving through a six-centre transition state structure. The valuable insights into mechanistic intricacies of aluminium-mediated intramolecular HA reported herein will help guide the rational design of group 13 metal-based HA catalysts.

Graphical abstract: Aluminium-catalysed intramolecular hydroamination of aminoalkenes: computational perusal of alternative pathways for aminoalkene activation

Supplementary files

Article information

Article type
Paper
Submitted
11 Jan 2015
Accepted
16 Mar 2015
First published
24 Mar 2015

Dalton Trans., 2015,44, 12169-12179

Author version available

Aluminium-catalysed intramolecular hydroamination of aminoalkenes: computational perusal of alternative pathways for aminoalkene activation

S. Tobisch, Dalton Trans., 2015, 44, 12169 DOI: 10.1039/C5DT00121H

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