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7th April 2011 @ 09:19
Racemization experiments on [url=]enantioenrichend ([i]S[/i])-(+)-PZQamine[/url] with Rhodium on charcoal [data=size:500x180]1037[/data] See also: [*] [url=]Racemization of S-(+)-PZQamine with Pd/C (MW50-1 to MW50-3)[/url] [*] [url=]Racemization of S-(+)-PZQamine with Pd/C (MW50-4)[/url] [*] [url=]Racemization of S-(+)-PZQamine with Raney Nickel (MW50-6, MW50-7)[/url] [*] [url=]Thiyl radical-mediated racemization of S-(+)-PZQamine (MW50-8)[/url] [*] [url=]Racemization of S-(+)-PZQamine (MW50-9) and (R) -(-)-PZQ (MW55-5) with sodium naphthalide[/url] [*] [url=]Repetition: Racemization of S-(+)-PZQamine (MW50-10) and R -(-)-PZQ (MW55-6) with sodium naphthalide[/url] [*] [url=]Racemization of S-(+)-PZQamine with Raney Nickel under high pressure and high temperature (MW50-11)[/url] [b]Hazard and Risk Assessment:[/b] [data]735[/data] Start time: 7:00 PM 7/04/2011 End time: 10:00 AM 11/04/2011 To a solution of [url=]enantioenrichend ([i]S[/i])-PZQamine[/url] (20 mg, 98.9 µmol, MW: 202.3 g/mol) in toluene (2 mL) was added Rhodium/Charcoal (10.2 mg, 9.89 µmol, 0.1 eq.; 10% Rh on C, M.W. (Rh) 102.9 g/mol) and heated to 70°C for 4 days. The mixture was filtered and evaporated under reduced pressure to give 18.8 mg of PZQamine. TLC (ethyl acetate/methanol/triethylamine, 1:1:0.02, stain: ninhydrin) [data]1059[/data] [data=text]1055[/data]: PZQamine /no side products visible [α]D20 = +98° (c=1, DCM) -> [b]Racemization ?! [/b](it's not clear if the lower [α] is a result of a reacemization or lower concentration of ([i]S[/i])-PZQamine caused by solvent impurities/ other impurities) -> Repeat a scaled-up reaction with an higher catalyst load, longer reaction time and higher temperature, see: [url=]Repetition: Racemization of (S)-PZQamine (MW50-13) with Rh/C[/url]
Attached Files
Scheme MW50-8.png
1H NMR MW50-12.pdf
1H NMR MW50-12 JCAMP-DX.dx
TLC MW50-12.jpg