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17th January 2011 @ 03:59
Racemization experiments of enantioenrichend [i]S[/i]-(+)-PZQamine with Pd/C obtained from [url=http://www.ourexperiment.org/racres_pzq/1309]Multigram-scale racemic resolution of praziquanamine with (-)-Dibenzoyl-L-tartaric acid (MW49-13)[/url] [data=size:500x180]733[/data] See also: [*] [url=http://www.ourexperiment.org/rac_pza/1499]Racemization of S-(+)-PZQamine with Pd/C (MW50-4)[/url] [*] [url=http://www.ourexperiment.org/rac_pza/1507]Racemization of S-(+)-PZQamine with Pd/BaSO4 (MW50-5)[/url] [*] [url=http://www.ourexperiment.org/rac_pza/1511]Racemization of S-(+)-PZQamine with Raney Nickel (MW50-6, MW50-7)[/url] [*] [url=http://www.ourexperiment.org/rac_pza/1729]Thiyl radical-mediated racemization of S-(+)-PZQamine (MW50-8)[/url] [b]Hazard and Risk Assessment:[/b] [data]735[/data] Start time: 3:50 PM 17/01/2011 End time: 1:40 PM 18/01/2011 To a solution of [i]S[/i]-(+)-PZQamine (50 mg, 248 µmol, MW: 202.3 g/mol) in toluene (5 mL) was added Pd/C (for 1% Pd: 2.62 mg, 2.48 µmol; for 5% Pd: 13.1 mg, 12.4 µmol; 10% Pd on charcoal, M.W. (Pd) 106.4 g/mol) and heated to 70°C for 3 / 22 h. The catalyst was filtered off by a filter paper and the solvent was evaporated. Notes: - almost complete amount of starting material was reisolated - color of the starting material turned from pale yellow to yellow Starting material [i]S[/i]-(+)-PZQamine [α]D20 = +170° (c=1, DCM) [b]MW50-1[/b] 1% Pd, 3 h [α]D20 = +156° (c=1, DCM) [b]MW50-2[/b] 5% Pd, 3 h [α]D20 = +131° (c=1, DCM) [data=text]737[/data] -> no decomposition / side reaction of the starting material [b]MW50-3[/b] 1% Pd, 2 h [α]D20 = +152° (c=1, DCM) [b]Results:[/b] - slow racemization of S-(+)-PZQamine with 1% Pd/C under the conditions stated above -> increase of temperature and catalyst loading (5% Pd) [b]References:[/b] [1] "Fast racemization and dynamic kinetic resolution of primary benzyl amines", Y. Kim, J. Park and M.-J. Kim, Tetrahedron Letters [b]2010[/b],[i]51[/i], 42, 5581-5584, [url=http://dx.doi.org/10.1016/j.tetlet.2010.08.050](http://dx.doi.org/10.1016/j.tetlet.2010.08.050)[/url] [2] "Lipase/Palladium-Catalyzed Asymmetric Transformations of Ketoximes to Optically Active Amines", Y. K. Choi, M. J. Kim, Y. Ahn, and M.-J. Kim, [i]Org. Lett.[/i] [b]2001[/b], [i]3[/i], 25, 4099–4101; [url=http://dx.doi.org/10.1021/ol0168622]DOI: 10.1021/ol0168622[/url]
Attached Files
Scheme MW50-1.png
HRAF MW50.pdf
1H NMR MW50-2.pdf