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A General Method for the Enantioselective Hydrogenation of β‐Keto Esters using Monodentate Binaphthophosphepine Ligands
Author(s) -
Hagemann Bernhard,
Junge Kathrin,
Enthaler Stephan,
Michalik Manfred,
Riermeier Thomas,
Monsees Axel,
Beller Matthias
Publication year - 2005
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200505131
Subject(s) - chemistry , denticity , enantioselective synthesis , propionate , catalysis , medicinal chemistry , selectivity , aryl , ligand (biochemistry) , asymmetric hydrogenation , yield (engineering) , ethyl acetoacetate , stereochemistry , organic chemistry , crystal structure , alkyl , receptor , biochemistry , materials science , metallurgy
17 monodentate phosphepine ligands with a 4,5‐dihydro‐3 H ‐dinaphtho[2,1‐ c ;1′,2′‐ e ]phosphepine structural motif have been synthesized and tested in the asymmetric hydrogenation of various β‐keto esters. By variation of the substituents of the aryl group on the phosphorus atom a fine tuning of the selectivity of the catalytic system is possible. Quantitative yield and enantioselectivities up to 95% ee have been achieved for the hydrogenation of methyl acetoacetate ( 7a ), methyl 3‐oxovalerate ( 7b ) and ethyl 4‐phenyl‐3‐oxo‐propionate ( 7d ) using 4‐(4‐methoxyphenyl)‐4,5‐dihydro‐3 H ‐dinaphtho‐[2,1‐c;1′,2′‐ e ]phosphepine ( 4g ) as ligand. Best enantioselectivities were obtained at comparably high temperatures (100–120 °C), which had the advantage of increased reaction rates.