On the mechanism of B(C6F5)3-catalyzed direct hydrogenation of imines: Inherent and thermally induced frustration

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Abstract

The reaction mechanism for the transition metal free direct hydrogenation of bulky imines catalyzed by the Lewis acid B(C6F5) 3 is investigated in detail by quantum chemical calculations. A recently introduced mechanistic model of heterolytic hydrogen splitting that is based on noncovalent association of bulky Lewis acid-base pairs is shown to account for the reactivity of imine-borane as well as amine-borane systems. Possible catalytic cycles are examined, and the results provide solid support for the imine reduction pathway proposed from experimental observations. In addition, the feasibility of an autocatalytic route initiated by amine-borane hydrogen cleavage is demonstrated. Conceptual issues regarding the notion of frustration are also discussed. The observed reactivity is interpreted in terms of thermally induced frustration, which refers to thermal activation of strained dative adducts of bulky Lewis donor-acceptor pairs to populate their reactive frustrated complex forms.

Original languageEnglish
Pages (from-to)2029-2036
Number of pages8
JournalJournal of the American Chemical Society
Volume131
Issue number5
DOIs
Publication statusPublished - Feb 11 2009

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ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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