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Continuous Flow Hydrogenation of Functionalized Pyridines
Author(s) -
Irfan Muhammed,
Petricci Elena,
Glasnov Toma N.,
Taddei Maurizio,
Kappe C. Oliver
Publication year - 2009
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200801131
Subject(s) - chemistry , catalysis , hydrogen , selectivity , flow chemistry , metal , stereoselectivity , solvent , continuous flow , electrolysis , transfer hydrogenation , noyori asymmetric hydrogenation , heterogeneous catalysis , organic chemistry , inorganic chemistry , ruthenium , electrode , physics , mechanics , electrolyte
The heterogeneous hydrogenation of substituted pyridines has been accomplished by employing a continuous flow hydrogenation device that incorporates in situ hydrogen generation by electrolysis of H 2 O and pre‐packed catalyst cartridges. In general, the hydrogenation reactions proceeded smoothly regardless of the supported precious metal catalyst (Pd/C, Pt/C, or Rh/C). By using 30–80 bar of hydrogen pressure at 60–80 °C full conversion was typically achieved in all cases at a flow rate of 0.5 mL min –1 , providing the corresponding piperidines in high yields. For disubstituted pyridines, variations in stereoselectivity were observed depending on both the metal catalyst and the temperature/pressure of the hydrogenation reaction. For ethyl nicotinate the selectivity between partial and full hydrogenation could be tuned depending on the hydrogen pressure, solvent, and the choice of supported metal catalyst. Changing the hydrogen source from H 2 O to D 2 O allowed the preparation of deuteriated derivatives. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)