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Autoinduced Catalysis and Inverse Equilibrium Isotope Effect in the Frustrated Lewis Pair Catalyzed Hydrogenation of Imines
Author(s) -
Tussing Sebastian,
Greb Lutz,
Tamke Sergej,
Schirmer Birgitta,
MuhleGoll Claudia,
Luy Burkhard,
Paradies Jan
Publication year - 2015
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.201500805
Subject(s) - frustrated lewis pair , chemistry , catalysis , imine , boranes , kinetic isotope effect , lewis acids and bases , amine gas treating , medicinal chemistry , inverse , activation energy , catalytic hydrogenation , computational chemistry , stereochemistry , organic chemistry , deuterium , quantum mechanics , boron , physics , geometry , mathematics
The frustrated Lewis pair (FLP)‐catalyzed hydrogenation and deuteration of N‐ benzylidene‐ tert‐ butylamine ( 2 ) was kinetically investigated by using the three boranes B(C 6 F 5 ) 3 ( 1 ), B(2,4,6‐F 3 ‐C 6 H 2 ) 3 ( 4 ), and B(2,6‐F 2 ‐C 6 H 3 ) 3 ( 5 ) and the free activation energies for the H 2 activation by FLP were determined. Reactions catalyzed by the weaker Lewis acids 4 and 5 displayed autoinductive catalysis arising from a higher free activation energy (2 kcal mol −1 ) for the H 2 activation by the imine compared to the amine. Surprisingly, the imine reduction using D 2 proceeded with higher rates. This phenomenon is unprecedented for FLP and resulted from a primary inverse equilibrium isotope effect.