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20th January 2011 @ 06:30
Racemization experiments of enantioenrichend S-(+)-PZQamine, obtained from Multigram-scale racemic resolution of praziquanamine, with (-)-Dibenzoyl-L-tartaric acid (MW49-13), with Raney nickel

Scheme MW50-6.png

See also:
Racemization of S-(+)-PZQamine with Pd/C (MW50-1 to MW50-3)
Racemization of S-(+)-PZQamine with Pd/C (MW50-4)
Racemization of S-(+)-PZQamine with Pd/BaSO4 (MW50-5)
Thiyl radical-mediated racemization of S-(+)-PZQamine (MW50-8)

Hazard and Risk Assessment:
HRAF MW50.pdf

Start time: 6:00 PM 20/01/2011
End time: 24/01/2011

To a solution of S-(+)-PZQamine (20 mg, 98.9 µmol, MW: 202.3 g/mol) in ethanol (3 mL) was added Raney nickel (291 µg, 4.95 µmol, 0.05 eq.; 2.9 mg suspension of Raney nickel (Suspension in water ~0.1 g/mL), M.W. (Ni) 58.7 g/mol) and heated to 70°C for XX h.

Stirring bar can't be used, because the paramagnetic nickel adhere to the magnet

under air -> almost no racemization after 1 day

under hydrogen atmosphere (1 bar)
[α]D20 = +85° (c=1, DCM) -> slow racemization after 4 days

[1] "Heterogeneous Raney Nickel and Cobalt Catalysts for Racemization and Dynamic Kinetic Resolution of Amines", A. Parvulescu, P. Jacobs, D. De Vos, Adv. Synth. Catal. 2008, 350, 113-121.(DOI: 10.1002/adsc.200700336)
Attached Files
Scheme MW50-6.png