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Mechanism and exo ‐Regioselectivity of Organolanthanide‐Mediated Intramolecular Hydroamination/Cyclization of 1,3‐Disubstituted Aminoallenes: A Computational Study
Author(s) -
Tobisch Sven
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200501017
Subject(s) - hydroamination , regioselectivity , intramolecular force , chemistry , protonation , stereoselectivity , dissociation (chemistry) , stereochemistry , reactivity (psychology) , catalysis , adduct , computational chemistry , organic chemistry , medicine , ion , alternative medicine , pathology
The complete catalytic reaction course for the organolanthanide‐assisted intramolecular hydroamination/cyclization (IHC) of 4,5‐heptadien‐1‐ylamine by a prototypical [(η 5 ‐Me 5 C 5 ) 2 LuCH(SiMe 3 ) 2 ] precatalyst has been critically scrutinized by employing a reliable DFT method. A computationally verified mechanistic scenario for the IHC of 1,3‐disubstituted aminoallene substrates has been proposed that is consistent with the empirical rate law determined by experiment and accounts for crucial experimental observations. It involves kinetically rapid substrate association and dissociation equilibria, facile and reversible intramolecular allenic CC insertion into the LnN bond, and turnover‐limiting protonation of the azacycle's tether functionality, with the amine‐amidoalleneLn adduct complex representing the catalyst's resting state. This mechanistic scenario bears resemblance to the mechanism that has been recently proposed in a computational exploration of aminodiene IHC. The unique features of the IHC of the two substrate classes are discussed. Furthermore, the thermodynamic and kinetic factors that control the regio‐ and stereoselectivity of aminoallene IHC have been elucidated. These achievements have provided a deeper insight into the catalytic structure–reactivity relationships in organolanthanide‐assisted cyclohydroamination of unsaturated CC functionalities.