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21st February 2011 @ 08:37
Attempts to the acid-mediated cyclization of the dimethoxy-N-benzoyl-protected Ugi intermediate MW52-1 with methanesulfonic acid

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Hazard and Risk Assessment:
HRAF MW53.pdf


Start time: 7:10 PM 21/02/2011
End time: 7:30 PM 21/02/2011

MW54-1:
MW52-1 (36 mg, 83.7 µmol, M.W. 430.5 g/mol) was stirred with methanesulfonic acid (0.5 mL) for 14 h at room temperature.
- work-up: neutralized with Na2CO3, extracted with DCM, dried with Na2SO4, evaporated
Data: 1H NMR MW54-1.pdf

MW54-2:
MW52-1 (30 mg, 69.8 µmol, M.W. 430.5 g/mol) was stirred with formic acid (0.5 mL) for 14 h at room temperature.
- work-up: neutralized with Na2CO3, extracted with DCM, dried with Na2SO4, evaporated
Data: 1H NMR MW54-2.pdf

-> no specific signals in NMR visible

TLC (Rf=0.31; ethyl acetate, 100%; stain: potassium permanganate): same Rf for starting material and product, product stains without heating and more intense.
Stain: ceric ammonium molybdate: product stains more greenish and paler than the starting material.

MW54-1: Product and side product (small amout of product, no starting material, lots of side product)
MW54-2: minor side products (NMR: no starting material visible)
-> reaction with formic acid is more selective

TLC.JPG



Related reactions:
Synthesis of the dimethoxy-N-benzoyl-derivative of PZQ via Pictet-Spengler reaction (MW54-3)
Acid-catalyzed Pictet-Spengler reaction with binaphthalenedisulfonic acid (MW56-1 to MW56-4)
Acid-catalyzed Pictet-Spengler reaction with methanesulfonic acid (MW56-5 to MW56-8)

References:
[1] Polycyclic Compounds by Ugi−Pictet−Spengler Sequence, W. Wang†, S. Ollio†, E. Herdtweck and A. Doemling, J. Org. Chem. 2011, 76 (2), pp 637–644. (DOI: 10.1021/jo102058s)
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Attached Files
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1H NMR MW54-1.pdf
1H NMR MW54-2.pdf
TLC.JPG