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Enantioselective Hydrogenation and Transfer Hydrogenation of Bulky Ketones Catalysed by a Ruthenium Complex of a Chiral Tridentate Ligand
Author(s) -
DíazValenzuela M. Belén,
Phillips Scott D.,
France Marcia B.,
Gunn Mary E.,
Clarke Matthew L.
Publication year - 2009
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.200801929
Subject(s) - enantioselective synthesis , ruthenium , transfer hydrogenation , noyori asymmetric hydrogenation , ligand (biochemistry) , chemistry , chiral ligand , asymmetric hydrogenation , combinatorial chemistry , organic chemistry , catalysis , receptor , biochemistry
A study on the enantioselective hydrogenation of tertiary alkyl ketones catalysed by a novel class of tridentate–Ru complex is reported. In contrast to the extensively studied [RuCl 2 (diphos)(di‐primary amine)] complexes, this new class of hydrogenation catalyst smoothly reduces these less reactive bulky ketones with up to 94 % ee . The same catalyst system can also selectively reduce other potentially problematic substrates such as bulky heterocyclic ketones. Unusually for a pressure hydrogenation catalyst, similar enantioselectivity can be obtained under transfer hydrogenation conditions. The transfer hydrogenations are somewhat slower than the pressure hydrogenations, but this drawback is readily overcome, since we have discovered that a microwave accelerated transfer hydrogenation of the above ketones occurs within 20 min at about 90 °C with similar selectivity to that obtained in the pressure hydrogenation system.